|
ScienceWeek
SCIENCE-WEEK
A Weekly Email Digest of the News of Science
A journal devoted to the improvement of communication
between the scientific disciplines, and between scientists,
science educators, and science policy-makers.
June 29, 2001 -- Vol. 5 Number 26
-----------------------------------------------
All sciences are considered by their professors
as equally significant; by the politicians, as
equally incomprehensible; and by the military as
equally expensive.
-- Don K. Price
-----------------------------------------------
=-=-=-=-=-=-=-=-=
Section 1
=-=-=-=-=-=-=-=-=
Contents of this Issue (Full reports in Section 2):
1. IN BRIEF:
Evidence against molecular clock hypothesis... US government
report supports stem cell research... Genetic analysis of Indian
castes... Languages in bacteria... Copper in biological
systems... Quantum computing based solely on geometric
manipulations... Proposed new approach to x-ray analysis of
macromolecular structure... Evolution of planetary rotation...
Aerosol climate forcing... Acoustic oscillations and Hot Big
Bang.
2. NEUROBIOLOGY:
PLASTICITY AND HORMONE RESPONSE OF THE ADULT BRAIN
An investigation of the effect of estrogen on synaptic
connectivity in the adult rat brain provides another example of
steroid hormones altering adult neuroanatomy, and another example
of how patterns of neural connections can be reorganized in the
adult brain. The results have implications for catamenial
epilepsy in female humans.
3. ANTHROPOLOGY:
HAND MORPHOLOGY AND TOOL USE BY NEANDERTHALS AND EARLY MODERN
HUMANS OF THE NEAR EAST
A 3-dimensional morphometric analysis of the hand remains of
early modern humans and Neanderthals supports the idea of
significant behavioral differences between these groups and
indicates that an important shift in human manipulative behaviors
was associated with the earliest stages of the emergence of
modern humans.
4. EARTH SCIENCES:
GREENHOUSE EFFECT: FIRST MEASUREMENT OF INCREASED LONGWAVE
RADIATION BLOCKADE
An analysis of the differences between the spectra of the ongoing
longwave radiation of the Earth as measured by orbiting
spacecraft in 1970 and 1997 provides direct experimental evidence
for a significant increase in the Earth's greenhouse effect that
is consistent with concerns over radiative forcing of the
climate.
5. GEOCHEMISTRY:
ON THE EARLY DEVELOPMENT OF AN OXYGEN-RICH EARTH ATMOSPHERE
A new proposal suggests that changes in the deep interior of the
Earth affected the composition of volcanic gases, and that this
led to the rise in atmospheric oxygen levels 2.5 billion years
ago.
6. MATERIALS SCIENCE:
SUPERCONDUCTIVITY: ON 50 YEARS OF THEORY
Unconventional superconductors suggest a new kind of magnetically
mediated superconductivity in which the quanta that glue
electrons into pairs are derived from magnetic fluctuations. In
many kinds of unconventional superconductors, it appears that the
glue that binds electrons together exists only as a fleeting
entity, rather than as a well-defined excitation.
7. IN FOCUS: WOMEN IN THE EARLY HISTORY OF GENETICS
William Bateson, one of the founders of modern genetics and the
first to hold a professorship in the subject, was also the first
to bring women into the field at a time when women in science
were largely scorned.
8. FROM THE SCIENCEWEEK ARCHIVE:
EMERGENT BEHAVIOR IN PHYSICS, CHEMISTRY, AND BIOLOGY
"Emergent behavior" is behavior apparently not predictable from
first principles but dependent on new principles emerging only at
higher levels of complexity. The essential question is, To what
extent are reductionist approaches to phenomena limited, and
where limits exist, what is to be done?
=-=-=-=-=-=-=-=-=
Section 2
=-=-=-=-=-=-=-=-=
1. IN BRIEF:
... ... MOLECULAR EVOLUTION: Complete genome projects are
revealing a remarkable genomic plasticity involving frequent
dynamic rearrangements, including those between related species.
O. Lecompte et al report comparison of three complete genomes of
hyperthermophilic Archaea, with data in disagreement with the
idea of a constant rate of nucleotide mutations (molecular clock
hypothesis). (Genome Research 2001 11:981)
... ... SCIENCE POLICY: Stem cells, the precursors to various
differentiated tissue cells, continue to excite researchers and
confuse politicians. A new report from the US National Institutes
of Health states that research on stem cells derived from both
human embryos and adult tissue promises "a dazzling array" of
treatments for various diseases, with embryonic stem cells
clearly superior for some purposes. (New York Times 27 Jun 01)
... ... MOLECULAR ANTHROPOLOGY: M. Barnshad et al report an
analysis of mitochondrial DNA in males of India from 8 castes of
different rank, the results interpreted as genetic evidence
concerning the origins of Indian caste populations. The authors
report their data demonstrates that the upper castes have a
higher affinity to Europeans than to Asians, and the upper castes
are significantly more similar to Europeans than are the lower
castes. The authors conclude that "Indian castes are most likely
to be of proto-Asian origin with West European admixture
resulting in rank-related and sex-specific differences in the
genetic affinities of castes to Asians and Europeans."
(Genome Research 2001 11:994)
... ... CELL BIOLOGY: S. Schauder and B.L. Bassler present an
analysis of the "languages" of bacteria. Bacteria communicate
with one another using chemical signaling molecules as "words".
Specifically, bacteria release, detect, and respond to the
accumulation of these molecules, which are called "autoinducers".
Detection of autoinducers allows bacteria to distinguish between
low and high cell population density, and to control gene
expression in response to changes in cell number. This process,
termed "quorum sensing", allows a population of bacteria to
control, in a coordinated manner, the gene expression of the
entire community. (Genes & Development 2001 15:1468)
... ... CELL BIOLOGY: In a commentary on genes involved in copper
metabolism, Nancy C. Andrews points out that not only is copper a
ubiquitous metal in our modern technological environment, but it
is also essential for the function of most living organisms. Just
as copper allows for the movement of electrons through wires,
copper helps catalyze the movement of electrons within biological
molecules. Making up only 0.01 percent of the Earth's crust,
copper is relatively scarce in the environment and must be
actively scavenged by biological organisms. It is ironic that
insights into copper metabolism initially came from experiments
aimed at understanding how cells take up iron.
(Proc. Natl. Acad. Sci. 2001 98:6543)
... ... QUANTUM COMPUTING: L-M. Duan et al propose an
experimentally feasible scheme to achieve quantum computing based
solely on geometric manipulations of a quantum system. The
desired geometric operations are obtained by driving the quantum
system to undergo appropriate cyclic evolutions. In this scheme,
all-geometric quantum computation is based on laser manipulation
of a set of trapped ions. The authors suggest that an all-
geometric approach, apart from its fundamental interest, offers a
possible method for robust quantum computation.
(Science 2001 292:1695)
... ... MOLECULAR BIOPHYSICS: In a proposal for a new approach to
x-ray determination of 3-dimensional structures of biomolecules,
J. Miao et al point out that although x-ray protein
crystallography is currently the primary method used in
determining the 3-dimensional structure of protein molecules at
near atomic or atomic resolution, approximately 20 to 40 percent
of all protein molecules, including important membrane proteins,
are difficult or impossible to crystallize, and thus their
structures have not been accessible by crystallography. The
authors propose a new technique involving the determination of
macromolecular structure by ultrashort intense x-ray pulses.
(Proc. Natl. Acad. Sci. 2001 98:6641)
... ... ASTROPHYSICS: Venus rotates very slowly on its axis in a
retrograde direction, opposite to that of most other bodies in
the Solar System. The general belief is that in the past the
rotational axis of Venus was itself rotated 180 degrees as a
result of core-mantle friction together with atmospheric tides.
Now A. Correla and J. Laskar, in a quantitative analysis,
demonstrate that terrestrial planets with dense atmospheres like
Venus can evolve into one of only four possible rotation states.
(Nature 2001 411:767)
... ... ATMOSPHERIC SCIENCE: R.J. Charlson et al, in a commentary
on recent research in atmospheric science, point out that droplet
clouds are the most important factor controlling the reflectivity
(albedo) and thus the temperature of Earth. Man-made aerosols
have a strong influence on cloud albedo, with a global mean
forcing estimated to be of the same order (but of opposite sign)
as that of greenhouse gases. However, the uncertainties
associated with aerosol forcing are large. Recent studies suggest
that both the forcing and its magnitude may be even larger than
anticipated. (Science 2001 292:2025)
... ... ASTROPHYSICS: C.J. Miller et al present an analysis of
acoustic oscillations in the early Universe. During its first
approximately 100,000 years, the Universe was a fully ionized
plasma with a tight coupling (by Thompson scattering) between
photons and matter. The trade-off between gravitational collapse
and photon pressure would cause acoustic oscillations in this
primordial fluid, and these oscillations should have left
predictable imprints in the spectra of the cosmic microwave
background radiation and the present-day matter-density
distribution. The authors make a comparison of recent acoustic
oscillation detections from two different cosmological epochs,
and suggest the results provide further support for the standard
"Hot Big Bang model" of the Universe. (Science 2001 292:2302)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
2. NEUROBIOLOGY:
PLASTICITY AND HORMONE RESPONSE OF THE ADULT BRAIN
In this context, the term "plasticity" is the name given to
the capacity of neural tissue to adjust to change. One variant of
this concerns the dependence of the "wiring" of the nervous
system on its input. Another variant concerns the dependence of
the wiring of the nervous system on endogenous chemical
alterations (e.g., hormone secretions). Still another variant
concerns the degree to which one region can under certain
conditions assume the function of another region. Plasticity does
not occur everywhere in the nervous system, but it is often
evident in the cerebral cortex of the brain, the cortex being the
thin layer of cells apparently responsible for higher analysis of
sensory input, language, ideation, and other so-called higher
functions lumped together in the category "cognitive processes".
Hormones are signaling molecules secreted into the blood
stream by endocrine cells and acting on target cells that possess
receptors for the hormone. Estrogen is a collective term for the
female hormones, the most powerful of which is *estradiol. They
control female secondary sexual characteristics, and prepare and
maintain the uterine lining. Estrogen affects the growth,
differentiation, and function of peripheral tissues of the
reproductive system, including the mammary gland, uterus, vagina,
and ovary. Estrogens also play an important role in bone
maintenance and exert cardioprotective effects. In the brain,
estrogens modulate physiological parameters important for
regulating procreation, including reproductive behavior,
*gonadotropin production and release from the pituitary, and
mood. In recent years it has become apparent that although
estrogen is best known for its critical role in influencing
female secondary sexual characteristics, reproductive cycle,
fertility, and maintenance of pregnancy, there are important
actions of estrogen in male tissues such as the prostate, testis,
and *epididymis. Estrogens are essential for the normal
development of bone tissue in the male, in addition to their
well-known role in female bone.
In general, nerve cells have a single long extension (the
"axon") that propagates the electrical output (the action
potential) of the cell. The term "synapse" refers to the junction
between the terminal of a neuron's axon and another neuron. When
studying the synapse, the first neuron is called the
"presynaptic" neuron, and the second neuron is called the
"postsynaptic" neuron.
In this context, the term "dendrites" refers in general to
input extensions of nerve cells. Dendrites may be extensively
branched. In general, dendrites are considered to receive input
and axons to propagate output, but the electrical architecture of
most neurons is complicated, and in many types of nerve cells
activation of the axon produces electrical activity that not only
propagates down the axon but also propagates backward through the
cell body and dendrites. During the past several decades, the
detailed anatomy of dendrites has been a focus of much research,
in particular the often-present parts of dendrites called
"dendritic spines". These spines are small (1 to 2 microns)
thorn-like protuberances along the length of a dendrite, and
there is evidence that such spines may be important components in
many kinds of neural microcircuits.
In addition to its ability to mediate specific functions, an
important property of the synapse is its small size. The area of
contact has a diameter of 0.5 to 2.0 microns, and the presynaptic
terminal ("bouton") has a diameter that characteristically is
only slightly larger. In the brain, neuroanatomists distinguish
"single-synapse boutons" and "multiple-synapse boutons",
depending on whether a terminal bouton makes contact with only
one spine or with several spines.
Concerning input to a nerve cell at the cellular level, in
most cases this input is the result of a neurotransmitter
substance by the presynaptic terminal(s), with various
transmitters producing various effects on the postsynaptic
neuron, the effects categorized as "excitatory" or "inhibitory",
depending on whether they tend to increase or decrease the firing
rate of the postsynaptic neuron.
The "hippocampus" is a brain cortex structure in the medial
part of the temporal lobe. In humans, among other functions, the
hippocampus is apparently involved in short-term memory, and
analysis of the neurological correlates of learning behavior in
the rat indicates that the hippocampus is also involved in memory
in that species.
Hypersynchronous discharge of groups of neurons in the brain
can produce the motor symptoms of seizure activity if these
neurons are directly or indirectly connected to the part of the
brain controlling peripheral muscle tissue. When seizures are a
chronic syndrome, a diagnosis of "epilepsy" is usually made, but
it is important to understand that the term "epilepsy" refers to
chronic seizures produced by any cause, e.g., trauma, infection,
genetic dysfunction, neuroactive drugs, etc. Thus epilepsy is not
a unitary disease; it rather a label for a collection of
symptoms. The term "catamenial epilepsy" refers to a disorder
that occurs only in women, and the frequency of seizures in this
disorder is apparently linked to certain phases of the menstrual
cycle, with some suggestion that the condition may be explained
by heightened neuronal excitability due to an increased number of
dendritic spines on certain neurons in the hippocampus
(hippocampal pyramidal neurons).
... ... M. Yankova et al (3 authors at Northwestern University,
US) present an experimental study of the effects of estrogen on
synaptic connections in the hippocampus of the rat, the authors
making the following points:
1) The authors report that the overwhelming majority of
multiple-synapse boutons in estrogen-treated animals form
synapses with more than one postsynaptic cell. Thus, in addition
to increasing the density of excitatory synaptic input to certain
hippocampal neurons (pyramidal cells in the CA1 layer of the
hippocampus), estrogen also increases the divergence of input
from individual presynaptic boutons to multiple postsynaptic
neurons. The authors suggest these findings indicate the
formation of new synaptic connections between previously
unconnected hippocampal neurons.
2) The authors conclude: "The estrogen-induced increase in
different-cell multiple-synapse bouton contacts has important
implications for hippocampal physiology, particularly if those
multiple-synapse boutons reflect the establishment of new
synaptic connections between previously unconnected cells. One of
the most robust effects of estrogen on the hippocampus is a
decrease in the threshold for seizure activity. The enhanced
divergence of presynaptic input reported here is predicted to
increase synchronization of synaptically driven activity in
[layer CA1 of the hippocampus]. As such, these structural changes
may contribute significantly to increasing susceptibility to
synchronous discharge associated with seizures.
... ... In a commentary on this work, S.M. Breedlove and C.L.
Jordan (University of California Berkeley, US) state: "Mark your
scorecard to indicate another example of steroid hormones
altering adult neuroanatomy, and another example of how patterns
of neural connections can be reorganized in the adult brain.
Instead of asking whether new synapses can come or go, perhaps
now we should ask whether any particular synapse in the brain
remains unchanged for more than a short while."
-----------
M. Yankova et al: Estrogen increases synaptic connectivity
between single presynaptic inputs and multiple postsynaptic CA1
pyramidal cells: A serial electron-microscopic study.
(Proc. Natl. Acad. Sci. US 13 Mar 01 98:3525)
QY: Catherine S. Woolley: cwoolley@northwestern.edu
-----------
S.M. Breedlove and C.L. Jordan: The increasingly plastic,
hormone-responsive adult brain.
(Proc. Natl. Acad. Sci. US 13 Mar 01 98:2956)
QY: S. Marc Breedlove: breedsm@socrates.berekely.edu
-----------
Text Notes:
... ... *estradiol: 1,3,5(10)-estratriene-3,17beta-diol.
C(sub18)H(sub24)O(sub2). This is the natural hormone -- present
in pure form in the urine of pregnant mares and in the ovaries of
pigs.
... ... *gonadotropin: (gonadotrophin, gonadotrophic hormone)
Refers to a group of hormones capable of promoting growth and
function of the gonads.
... ... *epididymis: An elongated structure connected to the
surface of the testis, it stores and matures sperm cells.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 29Jun01
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
3. ANTHROPOLOGY:
HAND MORPHOLOGY AND TOOL USE BY NEANDERTHALS AND EARLY MODERN
HUMANS OF THE NEAR EAST
The structure and function of the human hand distinguishes
man from all other primates, since all other primates rely on
their forelimbs and hands as major organs of locomotion. The term
"hominid" refers in general to any primate in the human family,
and although fossil evidence for the evolution of the hands of
hominids is not plentiful, an apparent important feature of the
human hand is a truly opposable thumb that rotates so that it can
oppose the other four fingers. This, and other significant
anatomical features, provide the strength and nature of the grip
of the hand. Two main grips that are recognized in man are the
power grip, used when grasping something, and the precision grip,
used with a fine instrument.
The human group we call the "Neanderthals" lived in much of
Europe, part of Asia, and the Middle East between 150,000 to
probably less than 30,000 years ago. Neanderthals were the first
fossil humans to be discovered, and they have long been the focus
of anthropological investigation. More bones of Neanderthals are
known than for any other human-related (hominine) fossil group,
including 30 nearly complete skeletons, so the preoccupation of
the anthropology community with the Neanderthals is perhaps
understandable.
The Middle East ("Near East") has been a rich source of
human fossils, the first excavations beginning in the 1930s at
the cave sites of Skhul and Tabun on Mount Carmel in Israel, with
later excavations at Kebara (Mount Carmel), Amud (near the Sea of
Galilee), and Qafzeh (near Nazareth). Until a decade ago, the
Neanderthals were believed to predate the modern human population
in the Middle East, and to be in effect the ancestors of that
human population. But the current consensus, on the basis of
dating evidence, is that the Neanderthals and modern humans were
contemporaries in the Middle East, perhaps for as much as 40,000
years. The apparent temporal overlap of the two populations in
the Middle East has been a puzzle and a source of controversy.
The term "Paleolithic" (Old Stone Age) is essentially an
archeological term applied to Eurasia with approximate time-frame
segments as follows:
Upper Paleolithic: from 40,000 to 8000 years ago.
Middle Paleolithic: from 200,000 to 40,000 years ago.
Lower Paleolithic: from 2.5 million to 200,000 years ago.
Neanderthals lived by hunting and gathering, probably in
small, nomadic groups, an existence that evidently required
extraordinary strength. Their tool technology involved the
so-called "Levallois technique" to produce flakes that were then
further worked to yield as many as 60 different implements. For
the Neanderthals, this Middle Paleolithic technology is termed
"Mousterian", after a cave at Le Moustier in France. Mousterian
flakes could be used for many purposes, including cutting flesh,
scraping hides, and working wood. The "Levallois technique" is
named after the site in France where the first examples of such
tools were found. This tool-making technique involves the
preparation of a large stone "core" with a flat upper surface and
a convex lower surface. Broad flakes are detached from the core
by striking the core sharply at an angle on an anvil. The
resulting flakes are broad and thin.
Of importance in understanding research in Paleolithic man
is that evidence comes to us from three different fields,
anthropology, paleontology, and archeology, each field with
different methods, different biases, and a different focus.
... ... Wesley A. Niewoehner (University of New Mexico, US)
presents an analysis of Middle East Paleolithic fossil hands, the
author making the following points:
1) The author points out that the Near Eastern human fossil
and archeological records present a unique paleoanthropological
situation, because two morphologically distinct but
archaeologically very similar human groups, the late archaic
Neanderthals and the early modern Skhul/Qafzeh hominids existed
at approximately the same time. Near Eastern Neanderthals are
known from a number of 50,000- to 120,000=year-old sites in
Israel, Syria, and Iraq. Neanderthals were craniofacially
distinct, highly active, and comparatively very muscular. The
fossil remains from the approximately 50,000- to 100,000-year-old
site at Skhul and the approximately 100,000-year-old-site of
Qafzeh, both in Israel, are craniofacially more modern and less
muscular than Neanderthals. Both groups are associated with
Middle Paleolithic archeological data complexes, indicating they
used typologically and technologically similar toolkits for their
subsistence activities.
2) The author points out that observations that Neanderthals
were more heavily muscled, had stronger upper-limb bones, and
possessed unusual shapes and orientations of some upper-limb
joints relative to the Skhul/Qafzeh hominids, have led some
researchers to conclude that significant behavioral differences
must have been present, despite the association of the two groups
with similar Middle Paleolithic archeological data complexes.
3) The author presents a 3-dimensional morphometric analysis
of the hand remains of Skhul/Qafzeh hominids and Neanderthals.
The author reports that the Skhul/Qafzeh sample differs
significantly from the Neanderthals in many aspects of hand
functional anatomy. Given the correlations between changes in
tool technologies and functional adaptations seen in the hands of
Upper Paleolithic humans, the author concludes that the
Skhul/Qafzeh hand remains were adapted to Upper Paleolithic-like
manipulations. The author suggests these results support the
inference of significant behavioral differences between
Neanderthals and the Skhul/Qafzeh hominids and indicate that an
important shift in human manipulative behaviors was associated
with the earliest stages of the emergence of modern humans.
... ... In a commentary on this work, Steven E. Churchill (Duke
University, US) states: "Although many questions yet remain, this
study represents an important step in resolving contradictions in
our behavioral interpretations of the fossil and archeological
records of the Near Eastern Middle Paleolithic and in delineating
the adaptive characteristics of both groups of Mousterian
humans."
-----------
Wesley A. Niewoehner: Behavioral inferences from the Skhul/Qafzeh
early modern human hand remains.
(Proc. Natl. Acad. Sci. US 13 Mar 01 98:2979)
QY: Wesley A. Niewoehner: wesn@unm.edu
-----------
Stephen E. Churchill: Hand morphology, manipulation, and tool use
in Neandertals and early modern humans of the Near East.
(Proc. Natl. Acad. Sci. US 13 Mar 01 98:2953)
QY: Stephen E. Churchill: churchy@duke.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 29Jun01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ANTHROPOLOGY:
ISOTOPE EVIDENCE OF NEANDERTHALS AS PREDATORS
For many years after the discovery of the first Neanderthal
fossil in 1856, Neanderthal man was considered "a dim-witted
slouching brute". But Neanderthal fossil remains, in fact,
indicate Neanderthal man had a larger brain capacity (average
volume 1500 cubic centimeters) than modern humans (average volume
1360 cubic centimeters), and considering everything known about
the Neanderthals, many anthropologists now view Neanderthal man
as merely a group at one end of the spectrum of modern human
variation.
The Neanderthals have been found only in Europe and the
Middle East in sites dated at 120,000 to 35,000 years ago, and
perhaps up to 300,000 years ago in Spain. Neanderthals were
apparently culturally advanced in many ways. They made a variety
of tools and weapons from wood, bone, and stone, including
delicate arrowheads, hand axes, scrapers for removing fat from
animal skins, and tools for engraving designs on bone and stone.
Neanderthals also apparently made clothes from animal skins, used
fire extensively, lived in caves or bone and skin shelters, and
on the basis of burial remains, apparently had religious beliefs.
The Neanderthals apparently disappeared approximately 35,000
years ago, and whether they died off as a result of environmental
changes (e.g., retraction of the northern ice sheet), were killed
off by modern man, or were interbred with modern man and lost a
separate identity is still unresolved.
... ... M.P. Richards et al (6 authors at 6 installations, UK CA
US FR HR) present new evidence concerning Neanderthal diet, the
authors making the following points:
1) The authors point out that understanding Neanderthal diet
has implications for understanding Neanderthal land use, social
organization, and behavioral complexity. Yet despite the abundant
evidence for successful hunting techniques across Neanderthal
Eurasia, animal remains can indicate only hunting or scavenging
episodes; such remains cannot reveal predominant foods in the
diet over the long term. In contrast, the measurement of ratios
of the stable isotopes of carbon (C-13) and nitrogen (N-15) in
mammal bone *collagen provides an indication of aspects of diet
over the last few years of life, and such isotope evidence can
therefore provide direct information on Neanderthal diet.
2) The authors report that isotope analysis of two
Neanderthal fossils and associated animal fossils from Vindija
Cave, Croatia, indicate that the bulk of the dietary protein of
the Neanderthals came from animal sources. Comparison with animal
remains from this and other sites of similar age indicates that
the Vindija Neanderthal isotope values are similar to those of
other carnivores, and these results are very close to the results
for the earlier Late Pleistocene Neanderthals from France and
Belgium. Therefore, the authors suggest, the emerging picture of
the European Neanderthal diet indicates that although
physiologically the Neanderthals were presumably omnivores, they
behaved as carnivores, with animal protein the main source of
dietary protein. The authors suggest "this finding is in
agreement with the indirect archeological evidence and strongly
points to the Neanderthals having been active predators."
-----------
M.P. Richards et al: Neanderthal diet at Vindija and Neanderthal
predation: The evidence from stable isotopes.
(Proc. Natl. Acad. Sci. US 20 Jun 00 97:7663)
QY: Erik Trinkaus: trinkaus@artsci.wustl.edu
-----------
Text Notes:
... ... *collagen: The term "collagen" refers to a group
of fibrous proteins of very high tensile strength that form the
main component of connective tissue, cartilage, and bones in
animals.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 18Aug00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON THE NEANDERTHALS IN HUMAN EVOLUTION
About 10 kilometers east of Dusseldorf in Germany, in the valley
of the Dussel, there is a little town called Neander. One hundred
and forty-three years ago, in the summer of 1856, some workmen
broke into a cave to get at the limestone inside and discovered a
set of ancient bones. Most of the bones were smashed to bits by
the workmen, but some of the bones, including part of the skull,
survived, and the skeleton was soon recognized by anthropologists
as belonging to an ancient race of men who came to be known as
the Neanderthals. A Neanderthal fossil had actually been
discovered some years earlier in Gibraltar, but not recognized as
such. Neanderthal-like fossils have also been found in France,
Spain, Italy, Yugoslavia, Iraq, China, Java, and Israel. For more
than a century, one of the central questions in paleoanthropology
has been whether modern man evolved from this race -- or was the
Neanderthal a separate branch that became extinct?
... ... I. Tattersall and J.H. Schwartz present a review of
recent research in this area, the authors making the following
points:
1) Although many paleoanthropologists have lately begun to
look favorably on the view that Neanderthals merit species
recognition in their own right as Homo neanderthalensis, at least
as many paleoanthropologists still regard the Neanderthals as no
more than a strange variant of our own species, Homo sapiens.
This difference in viewpoint represents far more than a simple
matter of taxonomic hair-splitting, since if the Neanderthals are
considered as a single species they must be analyzed and
understood on their own terms. In contrast, if the Neanderthals
are merely subspecies variants of ourselves, they can be
dismissed as little more than an evolutionary epiphenomenon, a
minor and ephemeral appendage to the history of Homo sapiens.
2) Recently, Duarte et al (1999) proposed that the skeleton
of a 4-year-old child, unearthed in late 1998 at the 24,500-year-
old site of Lagar Velho in Portugal, represents not merely a
casual result of a Neanderthal/modern human mating, but rather is
the product of several millennia of hybridization among members
of the resident Neanderthal population and the invading Homo
sapiens.
3) In general, "Neanderthals" is the informal designation of
a morphologically distinctive group of large-brained *hominids
who inhabited Europe and western Asia between approximately
200,000 and less than 30,000 years ago. They are sharply
distinguished from modern humans by a wide range of cranial and
*postcranial characteristics, although they do share a number of
derived bony features with other members of the European/western
Asian hominid *clade that diversified in this part of the world
after approximately 500,000 years ago. Subsequent to
approximately 150,000 years ago, the Neanderthals appear to have
been the sole surviving species of this clade.
4) The Neanderthals were apparently highly successful over a
large region for a substantial period of time, but this situation
changed dramatically with the arrival in Europe of the first
modern humans, Homo sapiens. The evidence is that these "Cro-
Magnons" had begun to arrive both in eastern Europe and in the
far northeast of the Iberian Peninsula by approximately 40,000
years ago, and within little more than 10,000 years, the
Neanderthals were gone. The mechanism of their eviction has long
been debated, but there are four main possibilities. The first
and second of these possibilities, that the Neanderthals were
eliminated by the moderns in direct conflict or by indirect
economic competition, both imply the separate species status of
the Neanderthals, as does any combination of these two
possibilities. The alternative possibilities, that the
Neanderthals had simply evolved rapidly into moderns, or that the
genes of the invading moderns simply "swamped" those of the
Neanderthals, both imply some form of species continuity.
5) The authors suggest that the analysis by Duarte et al of
the Lagar Velho child's skeleton is "a brave and imaginative
interpretation" which the majority of paleoanthropologists will
consider unproven. The archeological context of Lagar Velho is
that of a typical *Gravettian burial, with no sign of *Mousterian
cultural influence, and the specimen itself lacks not only
derived Neanderthal characteristics, but also lacks any
suggestion of Neanderthal morphology.
6) the authors conclude: "The probability must thus remain
that this is simply a chunky Gravettian child, a descendant of
the modern invaders who had evicted the Neanderthals from Iberia
several millennia earlier. However, in this contentious and
poorly documented field, any new data are eagerly sought, and
Duarte et al's courageous speculations will doubtless spur much-
needed new research."
-----------
I. Tattersall and J.H. Schwartz: Hominids and hybrids: The place
of Neanderthals in human evolution.
(Proc. Natl. Acad. Sci. US 22 Jun 99 96:7117)
QY: Ian Tattersall: iant@amnh.org
-----------
Text Notes:
... ... *hominids: In general, any primate in the human family.
... ... *postcranial: In general, this refers to the skeleton
behind the cranium in a quadruped and below the cranium in a
biped.
... ... *clade: A "clade" is a cluster of taxa derived from a
single common ancestor.
... ... *Gravettian: A paleolithic culture in Europe extending
from approximately 30,000 to approximately 22,000 years ago.
... ... *Mousterian: See main report.
... ... *Levallois technique: See main report.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 3Sep99
-------------------
Related Background:
ON MODERN HUMAN ORIGINS
The study of human origins, the field called paleoanthropology,
has intrinsic difficulties because of the relative scarcity of
data, but these difficulties are magnified enormously by the
simple fact that paleoanthropology, in essence, represents a
species attempting to reconstruct its own early history. As might
be expected, an objective reconstruction, one without biases and
preconceptions, is far from easy... One of the important
questions concerning the Neanderthals is what happened to them?
Hypotheses have shifted back and forth since the first discovery
in 1856 of Neanderthal bones, with two major views. One view is
that the Neanderthals were the direct ancestors of modern
Europeans. The other view regards the Neanderthals as a side
branch of human evolution, with extinction as their fate. This
latter view is apparently the majority view in the
paleoanthropology community
.... ... G.A. Clark (Arizona State University, US) presents a
review of current research controversies and methods concerning
the transition from early humans to modern humans that apparently
occurred during the period from 50,000 to 10,000 years ago
(Middle-Upper Paleolithic transition). A central question is
whether the transition occurred abruptly or gradually. The author
makes the following points:
1) Insufficient data is only part of the reason the question
of human origins remains unresolved. Researchers in this area
come from various research traditions, and in each of these
traditions different assumptions about the remote human past
determine what is considered relevant data, which questions are
asked of the data, and how the data are interpreted. More data do
not remove the paradigmatic bias implicit within each research
tradition, and in consequence people from the different relevant
fields fail to communicate effectively.
2) The disciplines that contribute to the field (archeology,
human paleontology, and molecular biology) tend to be discovery-
driven and focused on methodology. The result is a common absence
of concern for the logic of inference underlying claims of
knowledge. European archeological studies of modern human origins
are a particularly good example of such epistemological naivete.
These studies are based on a century-old typological systematics
that emphasizes retouched stone tools, coupled with a set of
biases and preconceptions concerning the relationships between
developments in tool-making and developments of cultures.
3) On the surface, the voluminous literature produced by the
debate concerning modern human origins suggests an informed and
sophisticated interdisciplinary research in which data are
absorbed and digested, arguments assimilated, and methodologies
understood, compared, and evaluated. The author suggests "this is
a gross simplification of a much more complex reality."
4) The author concludes: "We are, in effect, consumers of
one another's research conclusions, but we select among
alternative sets of research conclusions in accordance with our
biases and preconceptions. These biases and preconceptions must
be subjected to critical scrutiny. As long as there is no
explicit concern with the logic of inference -- how we know what
we think we know about the past -- there can be no consensus."
-----------
G.A. Clark: Highly visible, curiously intangible.
(Science 26 Mar 99 283:2029)
QY: G.A. Clark: gaclark@asu.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 28May99
-------------------
Related Background:
HUMAN EVOLUTION: THE FATE OF THE NEANDERTHALS
The current consensus in paleoanthropology is that the
Neanderthals were an extinct side-line of human evolution.
European Neanderthals are thought to have diverged from the
lineage that gave rise to modern humans at least 500,000 years
ago. The current view is that approximately 30,000 to 40,000
years ago the Neanderthals were replaced by modern populations,
probably from an ultimately African source. A present debate
concerns how this population replacement occurred.
... ... Paul Mellars, in a short review of a recent conference
(28-30 Aug 1998, Gibraltar, UK) on the Neanderthals, makes the
following points: 1) The current consensus is that in the
southern part of the Spanish peninsula, roughly to the south of
the Ebro valley, the local Neanderthals survived for at least
5000 to 10,000 years after the arrival of modern populations in
the adjacent parts of northern Spain and the Mediterranean coast.
2) The most likely explanation for the prolonged coexistence of
these two populations lies in the ecological differences between
the northern and southern parts of the Iberian peninsula. 3)
Studies of Neanderthal skeletal remains reinforce the conclusion
that the Neanderthals were a divergent lineage that probably made
no contribution to the evolution of anatomically modern humans.
This is consistent with the DNA evidence that the two lineages
separated at least 500,000 years ago, and even longer divergence
times are favored by some researchers. 4) The impression at the
end of the conference was that the Neanderthals were really quite
different from humans -- well adapted to survive in the harsh
glacial environments of Europe, but with distinct anatomical and
behavioral patterns different from their modern human successors.
The author concludes: "The eagerness of some scientists to claim
close kinship with the Neanderthals could come close to denying
that human evolution actually took place."
-----------
Paul Mellars (University of Cambridge, UK)
The fate of the Neanderthals.
(Nature 8 Oct 98 395:539)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 6Nov98
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
4. EARTH SCIENCES:
GREENHOUSE EFFECT: FIRST MEASUREMENT OF INCREASED LONGWAVE
RADIATION BLOCKADE
Chlorofluorocarbons (CFCs) are any of several organic
compounds composed of carbon, fluorine, chlorine, and hydrogen,
and are manufactured under the trade name "Freon". Two such
compounds of wide application are trichlorofluoromethane (CFC-11)
and dichlorodifluoromethane (CFC-12), both used extensively as
aerosol-spray propellants, refrigerants, solvents, and foam-
blowing agents. Although these compounds are convenient because
they are nontoxic and nonflammable, they collect in the
stratosphere, where they are split into constituents by solar
radiation, with chlorine interacting with and removing ozone from
the protective ozone layer that shields living organisms on Earth
from harmful ultraviolet rays.
The term "greenhouse effect" refers to the blockade of
longwave radiation from the Earth into space by trace
constituents of the atmosphere, primarily water vapor, carbon
dioxide, ozone, methane, nitrous oxide, and various
chlorofluorocarbons -- gases referred to collectively as the
"greenhouse gases".
These days, the greenhouse effect is much in the public mind
as a possible cause of near-future global warming. But the
sensitivity of the biosphere to the greenhouse effect has existed
throughout the history of life on Earth: the longwave-blocking
(infrared radiation-blocking) gases return radiated heat to the
ground, accounting for approximately 70 percent of the net input
of energy to the Earth's surface. If the atmosphere were without
water and carbon dioxide (the main infrared blockers), the
surface temperature of the Earth in the present temperate
latitudes would be at approximately -20 degrees celsius in summer
and large portions of the planet would be covered by ice. We owe
the habitability of this planet to the greenhouse effect; the
problem is that future increases in the effect due to the escape
of industrial waste into the atmosphere may cause drastic changes
in climate, sea-level, and ecological balances -- all of these
with more or less unpredictable consequences.
In this context, the term "hydrologic cycle" refers in
general to the continuous circulation of water between the
oceans, atmosphere, and land, with water evaporating from the
surface to become water vapor in the atmosphere, and then
condensing and precipitating as water back to the surface. Since
water-vapor is an important greenhouse gas, changes in the
hydrologic cycle can alter the greenhouse effect, in some cases
by a positive feedback loop that accelerates changes in both
phenomena.
... ... J.E. Harries et al (4 authors at Imperial College London,
UK) present a report of increases in the greenhouse effect in the
period 1970 to 1997, the authors making the following points:
1) The authors point out that the evolution of the climate
of Earth has been extensively studied, and a strong link between
increases in surface temperatures and greenhouse gases has been
established. But this relationship is complicated by several
feedback processes -- most importantly that involving the
hydrologic cycle -- that are not well understood. Changes in the
Earth's greenhouse effect can be detected from variations in the
spectrum of outgoing longwave radiation, which is a measure of
how the Earth cools by radiation into space, the spectrum
carrying the imprint of the gases that are responsible for the
greenhouse effect.
2) The authors report an analysis of the differences between
the spectra of the ongoing longwave radiation of the Earth as
measured by orbiting spacecraft in 1970 and 1997. They find
differences in the spectra that point to long-term changes in
atmospheric methane, carbon dioxide, and ozone, as well as CFC-11
and CFC-12. The authors suggest their results provide direct
experimental evidence for a significant increase in the Earth's
greenhouse effect that is consistent with concerns over radiative
forcing of the climate. The authors conclude: "The results
presented here provide (to our knowledge) the first experimental
observation of a change in the Earth's outgoing longwave
radiation spectrum, and therefore the greenhouse effect: previous
studies have been largely limited to theoretical simulations
because of the paucity of data."
-----------
J.E. Harries et al: Increases in greenhouse forcing inferred from
the outgoing longwave radiation spectra of the Earth in 1970 and
1997.
(Nature 15 Mar 01 410:355)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 29Jun01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
EARTH SCIENCES:
AN ALTERNATIVE SCENARIO FOR GLOBAL WARMING
Earth's global surface temperature has increased by
approximately 0.5 degrees centigrade since 1975, a relative
"burst" of warming that has apparently taken the global
temperature to its highest level in the past 1000 years, and
there is a growing consensus that the warming is at least in part
a consequence of increasing anthropogenic *greenhouse gases.
These gases cause a global "climate forcing", i.e., an imposed
perturbation of the energy balance of the Earth with space. There
are many competing natural and anthropogenic climate forcings,
but increased greenhouse gases are estimated to be the largest
forcing and to result in a net positive forcing, especially
during the past few decades. Evidence supporting this
interpretation has been provided by observed heat storage in the
ocean, which is positive and which is of the magnitude of the
energy imbalance estimated from climate forcings for recent
decades.
... ... J. Hansen et al (5 authors at 3 installations, US)
present a discussion of global warming, the authors making the
following points:
1) The authors point out that a common view is that the
current global warming rate will continue or accelerate. The
authors, however, argue that rapid warming in recent decades has
been driven mainly by non-carbon dioxide greenhouse gases such as
chlorofluorocarbons, methane, and N(sub2)O, and not by the
products of fossil fuel burning, carbon dioxide, and *aerosols,
the positive and negative climate forcings of which are partially
offsetting.
2) The authors point out that the growth rate of non-carbon
dioxide greenhouse gases has declined in the past decade. If
sources of methane and O(sub3) precursors were reduced in the
future, the change in climate forcing by non-carbon dioxide
greenhouse gases in the next 50 years could be near zero.
Combined with a reduction of *black carbon emissions and
plausible success in slowing carbon dioxide emissions, this
reduction of non-carbon dioxide greenhouse gases could lead to a
decline in the rate of global warming, reducing the danger of
dramatic climate change.
3) The authors suggest that such a focus on air pollution
has practical benefits that unite the interests of developed and
developing countries, although assessment of ongoing and future
climate change requires composition-specific long-term global
monitoring of aerosol properties.
-----------
[Editor's note: After its publication several weeks ago, this
paper became controversial and received considerable publicity.
The senior author, James Hansen, is noted for helping to alert
the world to global warming in 1988, and this recent paper has
been interpreted as a reversal of his ideas concerning the
dangers of fossil fuel, carbon dioxide, and aerosol emissions,
and publicized by those opposed to the Kyoto Protocol on climate
change. For an account of reaction to this paper, see:
Nature 7 Sep 00 407:7.]
-----------
J. Hansen et al: Global warming in the 21st century: An
alternative scenario.
(Proc. Natl. Acad. Sci. US 29 Aug 00 97:9875)
QY: James Hansen: jhansen@giss.nasa.gov
-----------
Text Notes:
... ... *greenhouse gases: The physical basis of the so-called
"*greenhouse effect" is essentially simple: carbon dioxide gas is
transparent to visible light but relatively opaque to infrared
radiation. The same is true of glass. Relatively high-energy
visible light radiation from the sun passes inward through the
atmosphere, warms the surface of the Earth, which then radiates
lower energy in the form of infrared radiation (heat) back to the
atmosphere. But if the atmosphere has a concentration of infrared
impenetrable gases such as carbon dioxide, the infrared radiation
cannot pass out, and the surface of the Earth underlying the
atmosphere cannot cool, and the surface of the Earth thus will
continue to grow hotter.
... ... *aerosols: The term "aerosol" refers to a dispersion in
which a finely divided solid is suspended in air and the
particles are of colloidal dimensions. The term "colloidal
dimensions" refers to the range approximately 1 nanometer to 100
nanometers in diameter.
... ... *black carbon: (carbon black) Amorphous (i.e., non-
crystalline) carbon.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 6Oct00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
CLIMATOLOGY:
ANTHROPOGENIC ATMOSPHERIC AEROSOLS AND GLOBAL CLIMATE CHANGE
... Aerosols are an important component of atmospheric chemical
dynamics, with the contributions of aerosols to global and
regional climate far from simple.
... ... S.E. Schwartz and P.R. Buseck (2 installations, US)
present a commentary on recent research on anthropogenic
atmospheric aerosols, the authors making the following points:
1) Most considerations of global climate change caused by
human activities have focused on the warming influence of
greenhouse gases. However, aerosols are another important
atmospheric constituent that influences climate and that has been
affected by human activities. In general, aerosol particles
increase scattering and absorption of shortwave (solar)
radiation, increase cloud reflectance, enhance cloud lifetimes,
and suppress precipitation. These phenomena are all thought to
exert a cooling influence on climate. Recent data indicate that
anthropogenic aerosols reduce cloud droplet size and suppress
precipitation downward of major urban areas and industrial
facilities, which is consistent with earlier hypotheses.
2) The influences of aerosols on climate are more complex
than those of greenhouse gases. Bulk aerosol composition is
highly variable spatially and temporally because of different
sources and production mechanisms and short atmospheric residence
times (from less than a day to more than a month). Particles
sizes range from nanometers to microns, and within the same size
class, particles can exhibit widely different compositions and
morphologies, with different constituents present within the same
particle (e.g., 10 nanometer carbon spherules can be found
embedded within much larger sulfate particles). The
inhomogeneities in properties and geographical distribution of
aerosols make it difficult to characterize their influences on
climate and to represent these influences in models.
3) Recent analysis of the consequence of absorption of
shortwave radiation by aerosols indicates that the heating of the
atmosphere can evaporate clouds. Clouds exert both cooling and
warming influences on climate: cooling in the shortwave (because
of their reflectance), and warming in the longwave (because of
absorption and re-emission of thermal infrared radiation). The
shortwave component dominates, so a reduction in cloud coverage
would result in a net warming influence.
5) The authors conclude: "Recent studies demonstrate both
the importance of aerosol effects on climate and the complexity
of aerosol-cloud interactions. Unfortunately for those would like
a quick and accurate assessment of anthropogenic climate forcing
over the industrial period, the studies also demonstrate that
there is much to be learned before such an assessment can
confidently be given."
-----------
S.E. Schwartz and P.R. Buseck: Absorbing phenomena
(Science 12 May 00 288:989)
QY: S.E. Schwartz [ses@bnl.gov]
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 23Jun00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON CLIMATE FORCINGS IN THE INDUSTRIAL ERA
A "climate forcing" is an imposed perturbation of the Earth's
energy balance with space, for example, a change of the solar
radiation incident on the planet, or a change of carbon dioxide
in the Earth's atmosphere. The unit of measure of climate forcing
is Watts per square meter. Thus, the forcing due to the increase
of atmospheric carbon dioxide since pre-Industrial times is
approximately 1.5 Watts per square meter. Climate change is
combination of deterministic response to forcings and *chaotic
fluctuations -- the chaos a consequence of the nonlinear
equations governing the dynamics of the system. Quantitative
knowledge of all significant climate forcings is needed to
establish the contribution of deterministic factors in observed
climate change and to predict future climate. J.E. Hansen et al,
in a review of current considerations concerning climate forcings
in the Industrial era, make the following points: 1) The forcings
that drive long-term climate change are not known with an
accuracy sufficient to define future climate change. 2)
Anthropogenic greenhouse gases, which are well-measured, cause a
strong positive (warming) force. But other, poorly measured,
anthropogenic forcings, especially changes of atmospheric
aerosols, clouds, and land-use patterns, cause a negative forcing
that tends to offset greenhouse warming. 3) One consequence of
this partial balance is that the natural forcing due to solar
irradiance changes may play a larger role in long-term climate
change than inferred from comparison with greenhouse gases alone.
Current trends in greenhouse gas climate forcings are smaller
than in popular "business as usual" or 1 percent per year carbon
dioxide growth scenarios. The authors suggest that a summary
implication of their considerations is a paradigm change for
long-term climate projections: uncertainties in climate forcings
have supplanted global climate sensitivity as the predominant
issue. The authors further suggest that climate forcing scenarios
are essential for climate predictions, but if only one forcing
scenario is used in climate simulations, as has been a recent
tendency, the scenario itself is likely to be taken as a
prediction, as well as the calculated climate change. The authors
recommend that the use of multiple scenarios will aid objective
analysis of climate change as it unfolds in coming years.
-----------
J.E. Hansen et al (6 authors at National Aeronautics and Space
Administration, US)
Climate forcings in the Industrial era.
(Proc. Natl. Acad. Sci. US 27 Oct 98 95:12753)
QY: James E. Hansen
-----------
Text Notes:
... ... *chaotic fluctuations: The term "chaotic", in this
context, is specific. In the study of physical systems, the
term "chaotic behavior" has a specific meaning: the behavior of a
system is said to be "chaotic" if its final state is so sensitive
to the system's precise initial conditions that the behavior of
the system is in effect unpredictable and cannot be distinguished
from a random process, even though the behavior of the system is
strictly determinate in a mathematical sense. In other words, a
deterministic system characterized by extremely sensitive
instabilities, despite the system being determinate, can exhibit
behavior that is unpredictable, and the system is then called
"chaotic". During the past several decades, the analysis of such
chaotic systems has intrigued both physicists and mathematicians.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 4Dec98
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON THE PERMIAN EXTINCTION AND THE GREENHOUSE EFFECT
In geology and paleontology, a "period" is a major subdivision of
an era of geological time distinguished by a particular system of
rocks and associated fossils. The Permian Period is the most
recent period of the Paleozoic Era, and occurred approximately
225 to 270 million years ago. The Permian was characterized by an
abundance of vertebrate and invertebrate forms, a proliferation
of reptilian forms, and a variety of vegetation forms. The
arrangement of the continents was apparently quite different than
at present, with a closer packing of land masses, and the
southern end of Africa well below the Antarctic circle. One of
the more interesting features of the Permian Period is that it
was apparently terminated by a mass biotic extinction of enormous
proportions. ... ... Peter D. Ward (University of Washington
Seattle, US), reviewing the Permian extinction and a current
model to explain it, makes the following points: 1) The Permian
extinction was the greatest mass extinction in Earth's history,
involving the extinction of 90 percent of the species in the
ocean and 70 percent of the species on land. Despite its scale,
the Permian extinction remains a deep mystery. 2) In the fossils
of the past 530 million years, there is evidence of many mass
extinctions, but evidence only of 5 extinctions that killed more
than half the extant species. The best known extinction is the
Cretaceous-Tertiary (also called K/T) event of 65 million years
ago, apparently caused by the impact of a comet or an asteroid,
the event characterized by the extinction of the dinosaurs. But
the K/T event destroyed only about 50 percent of the species on
Earth, which means it was a much less extensive extinction than
the Permian. 3) Knoll et al, in 1995, proposed that the Permian
extinction in the oceans was essentially caused by the release in
the ocean, due to movements of land masses, of carbon dioxide
trapped in sediments, and that it was ocean carbon dioxide, known
to be highly toxic to marine life, that was responsible for the
ocean mass biotic extinction. 4) In the current article, Ward
suggests that ocean carbon dioxide and volcanic gases, both
emerging into the atmosphere, resulted in a heating of the
atmosphere to critical levels. Ward proposes that the surge in
temperature is reflected in the common redness of rock strata
associated with the end of the Permian, the red color a result of
the rusting of iron compounds, and suggesting a climate change of
massive proportions. 5) The author suggests that the Permian
extinction now appears to be a new type of mass extinction,
unrelated to extraterrestrial causes, and occurring much faster
than typical extinctions triggered by internal changes to the
climate and chemistry of the Earth. The author concludes: "Are we
walking down the same path that killed off so much life 250
million years ago -- not from carbon dioxide liberated from the
oceans but from carbon dioxide liberated from our cars and
industry?"
-----------
QY: Peter D. Ward, Univ. of Washington Seattle 206-543-8992.
(Discover August 1998) (Science-Week 28 Aug 98)
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
5. GEOCHEMISTRY:
ON THE EARLY DEVELOPMENT OF AN OXYGEN-RICH EARTH ATMOSPHERE
It is currently believed that the oxygen concentration in
Earth's atmosphere may have remained at 1 percent of its present
level until approximately 2 billion years ago, after which the
concentration gradually increased to its present value with the
increasing success of photosynthetic life forms. Fossil oxygen-
generating cyanobacteria have been dated as far back as 3.5
billion years ago, but the rate at which oxygen accumulated in
the atmosphere because of photosynthesis is not known.
Although the time-frame of the increase in oxygen
concentration of the atmosphere is uncertain, the consensus among
researchers is that the initiation of an oxygen atmosphere
increased the number and kinds of organisms capable of using
aerobic metabolic pathways. By the start of the Cambrian period
570 million years ago, or somewhat earlier, oxygen levels had
apparently increased enough to permit rapid evolution of large
oxygen-utilizing multicellular organisms.
... ... Norman H. Sleep (Stanford University, US) presents a
commentary on recent research on the early atmosphere of Earth,
the author making the following points:
1) The author points out that although oxygen now
constitutes approximately 20 percent of the gas in the
atmosphere, before approximately 2.5 billion years ago it was
apparently only a trace constituent. The Earth is unique among
the planets in the Solar System in having an oxygenated
atmosphere. The atmospheres of the other planets are anoxic
because oxygen levels are kept relatively low by an equilibrium
system involving chemical processes in crusts, mantles, and
volcanic gases. On the Earth, oxygen levels increased over
geological time apparently mainly as a result of photosynthesis,
which can be expressed as the general reaction carbon dioxide -->
carbon + oxygen.
2) Over the eons, a vast amount of organic carbon has become
locked up in sedimentary rocks, a small part of it in coal and
oil, thus preventing the reverse reaction to equilibrium that
would create carbon dioxide and lower atmospheric levels of
oxygen. However the advent of oxygen-producing photosynthesis
cannot be the entire story of the evolution of Earth's
atmosphere, since photosynthesis apparently existed long before
the well-documented rise in oxygen levels 2.5 billion years ago
(the Archaean-Proterozoic transition).
3) L.R. Kump et al (Geochem. Geophys. Geosyst. 2001) are now
proposing that changes in the deep interior of the Earth affected
the composition of volcanic gases, and that this led to the rise
in atmospheric oxygen levels 2.5 billion years ago. The idea is
that although photosynthesis is presently the main source of
oxygen in Earth's atmosphere, it may have been geological
activity that first allowed an oxygen-rich atmosphere to develop.
4) The author (Sleep) concludes: "It was over two centuries
ago that Antoine Lavoisier figured out that we breathe oxygen.
But we still don't know how an oxygen-rich atmosphere arose.
Clearly, processes at both the Earth's surface and in its bowels
were involved. Exactly how and by how much each contributed
remain open questions."
-----------
Norman H. Sleep: Oxygenating the atmosphere.
(Nature 15 Mar 01 410:317)
QY: Norman H. Sleep: norm@pangea.stanford.edu
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 29Jun01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
EARTH SCIENCE: ATMOSPHERIC OXYGEN OVER PHANEROZOIC TIME
The term "Phanerozoic time" refers to the past 550 million years,
the time during which most higher organisms arose and evolved,
both in the oceans and on the continents. The evolution of
atmospheric oxygen over geologic time is believed to have been
both a major cause and a major effect of biological evolution,
since oxygen is both consumed by plant and animal respiration and
produced by photosynthesis. On a geologic time scale (i.e.,
millions of years) the global biogeochemical cycles of carbon and
sulfur, involving the exchange of reduced carbon and sulfur
between rocks and the atmosphere-plus-oceans, constitute the
major controls on the levels of oxygen. Therefore, the study of
these cycles and how they may have varied in the geological past
is important to the history of both the atmosphere and of Earth
surface environments.
... ... Robert A. Berner (Yale University, US) presents a review
of recent work in the field, the author making the following
points:
1) The processes that affect the evolution of atmospheric
oxygen as it relates to the carbon and sulfur cycles over
geologic time include the following:
... ... a) Input to the oceans of carbon dioxide and dissolved
carbonate and sulfate derived from oxidation, during chemical
weathering on the continents, of ancient organic matter and
pyrite [FeS(sub2)] in *sedimentary rocks.
... ... b) Reduction and removal of dissolved inorganic carbon
from sea water and fresh water via the synthesis of organic
matter, followed by a burial of dead organic remains in bottom
sediments.
... ... c) Removal of sulfate from seawater via bacterial
reduction to hydrogen sulfide followed by the reaction of
hydrogen sulfide to form sedimentary pyrite.
... ... d) The reaction of hot *basalt with sulfate in seawater
at mid-oceanic rises.
... ... e) Degassing of reduced carbon- and sulfur-containing
gases to the atmosphere-plus-oceans as a result of the thermal
decomposition of deeply buried organic matter and pyrite by
*diagenesis, *metamorphism, and volcanism. On arriving at the
Earth's surface, these reduced gases are rapidly oxidized by
oxygen.
2) In addition to the above carbon and sulfur cycles which
involve atmospheric oxygen, there are cycles important to carbon
and sulfur mass balance, particularly isotope mass balance, but
which do not involve atmospheric oxygen. These cycles include a)
the weathering of calcium carbonate and calcium sulfate minerals
on the continents, and b) the formation of these minerals in the
oceans followed by burial in sediments.
3) Calculation of the effect of changes in the global carbon
and sulfur cycles over geologic time on atmospheric oxygen has
been attempted with various models:
... ... a) Sediment composition models: In these models, the
chemical composition of sedimentary rocks of various ages is
combined with the abundance of these rocks (corrected for
postdepositional erosional/metamorphosic loss) to calculate the
original rates of burial of organic carbon and pyrite sulfur in
sediments.
... ... b) Nutrient models: In these models the burial rate of
organic carbon is assumed to be limited by the availability of
the nutrients nitrogen and phosphorus, which leads to
consideration of the cycles of these elements, as well as those
of carbon and sulfur.
... ... c) Isotope mass balance models: In these models, carbon
and sulfur isotopic data for seawater composition over geologic
time are used to calculate the values of fluxes.
A major problem with all models is the extreme sensitivity
of the mass of atmospheric oxygen to very small imbalances in the
burial and weathering fluxes.
4) One study using sediment abundance data, along with
assumed rapid recycling of sediments to stabilize oxygen, shows a
pronounced and extended rise in atmospheric oxygen over the
period 375 to 275 million years ago, spanning the *Carboniferous
and Permian periods. What could have brought this about? The
modeling indicates that increased oxygen production caused by
increased burial of organic carbon is the chief suspect. This
increased burial is attributed to the rise and spread of large
woody vascular plants on the continents beginning at about 375
million years ago. The plants supplied a new source of organic
matter to be buried on land and carried to the oceans via rivers.
This "new" carbon was added to that already being buried in the
oceans, thus increasing the total global burial flux.
-----------
Robert A. Berner: Atmospheric oxygen over Phanerozoic time.
(Proc. Natl. Acad. Sci. US 28 Sep 99 96:10955)
QY: Robert A. Berner [berner@hess.geology.yale.edu]
-----------
Text Notes:
... ... *sedimentary rocks: These are rocks formed by the
hardening of accumulated particles (sediments) that were
transported by agents such as wind and water. Such rocks are the
prime source of fossils.
... ... *basalt: Basalt is a dark gray to black igneous
rock of volcanic origin that cools rapidly. "Igneous rocks" are
rocks that have congealed from a molten mass.
... ... *diagenesis: In general, the term "diagenesis" refers to
all the changes that occur in a sediment at low temperature and
pressure after deposition. With increasing temperature and
pressure, diagenesis grades into "*metamorphism".
... ... *metamorphism: In general, the process of changing the
characteristics of a rock in response to changes in temperature,
pressure, or volatile content. Most metamorphic changes do not
include bulk chemical changes, but merely the crystallization of
new mineral phases. Examples of the transformation of
sediments through diagenesis and metamorphism are sand to
sandstone and peat to coal.
... ... *Carboniferous and Permian periods: The "Carboniferous
period" is the time-frame 362.5 to 290 million years ago. The
"Permian period" is the time-frame 290 to 245 million years ago.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 19Nov99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
A MOLECULAR DATING TEST OF THE CAMBRIAN EXPLOSION HYPOTHESIS
The early history of the *Metazoa, whether the Metazoa originated
as part of a *Cambrian "explosion" or with an extended
*Precambrian "phylogenetic fuse", remains controversial in
evolutionary biology. The Cambrian explosion hypothesis -- that
the phyla and even classes of the animal kingdom originated in a
rapid evolutionary radiation at the base of the Cambrian at 545
to 560 million years ago -- rests on the sudden appearance of a
diverse range of animals in the fossil record. Although recent
discoveries of *Ediacaran metazoans have extended the record of
sponges and bilateral animals to 570 million years ago, the
biological affinities of many Ediacaran organisms remains
controversial, and the earliest paleontological evidence of
metazoan life is no more than 600 million years ago. However, the
absence of earlier metazoan fossils could have been caused by
systematic biases in preservation that left the Precambrian
history of recognized phyla unrecorded in fossils. Molecular
studies have the potential to shed light on the origin of the
animal phyla by providing independent estimates of the divergence
times, but molecular studies have been criticized for failing to
account adequately for variations in rate of evolution.
... ... L. Bromham et al now present a study involving a method
of dating divergence times from molecular data (both
*mitochondrial DNA and nuclear DNA) which addresses the
criticisms of earlier studies, and which the authors state
provides more realistic but wider confidence intervals. The
authors report their data are not compatible with the Cambrian
explosion hypothesis as an explanation for the origin of metazoan
phyla, and they suggest their data provide additional support for
an extended period of Precambrian metazoan diversification. The
authors conclude: "Although we cannot provide precise estimates
of the origin of metazoan phyla, we can use our results to
confidently reject the Cambrian explosion hypothesis, which rests
on a literal interpretation of the fossil record and assumes that
special evolutionary phenomena, capable of producing profound
differentiation in a short period, operated in the Cambrian but
not before or since. By contrast, the Precambrian phylogenetic
fuse hypothesis assumes no more than we already know to be
reasonable: that lineages can diverge gradually over time and
that the fossil record contains gaps that can greatly reduce the
chances of finding fossils for certain periods or particular
types of organisms.
-----------
L. Bromham et al (3 installations, UK NZ)
Testing the Cambrian explosion hypothesis by using a molecular
dating technique.
(Proc. Natl. Acad. Sci. US 13 Oct 98 95:12386)
QY: Lindell Bromham: LBromham@zoology.uq.edu.au
-----------
Text Notes:
... ... *Metazoa: In general, the term "metazoa" refers to all
multicellular animals. Among important distinguishing
characteristics of metazoa are cell differentiation and
intercellular communication. For certain multicellular colonial
entities such as sponges, some biologists prefer the term
"parazoa".
... ... *Cambrian "explosion": The geological period known as the
Cambrian is the time frame from about 505 million years ago to
545 million years ago. Its most outstanding aspect is the rather
sudden appearance of numerous invertebrate fossils, so numerous
that some have termed it an explosion of evolutionary processes.
Many of the life forms that existed during the Cambrian are long
extinct, but their fossils are numerous, and through their
fossils the various Cambrian species have been the subject of
much study by paleobiologists. The Cambrian explosion of life
forms has been a long-standing puzzle for paleobiologists, and at
present there is apparently no single generally accepted
explanation. Among the ideas proposed have been, 1) that the
explosion of new forms resulted from a sudden increase in
atmospheric oxygen; 2) that the explosion is only apparent, and
the Precambrian, the period previous to the Cambrian, lacks
fossils because of heat and pressure associated with important
geological changes; 3) that living forms evolved mostly in
freshwater areas, and are therefore absent in Precambrian
sediments, which are primarily marine; 4) that changes in the
shape and extent of shorelines produced by continental drift
dramatically transformed climate and environment; 5) that the
previous evolution of DNA recombination and regulatory genes
culminated in and sparked the diversity and anatomical complexity
manifested in the explosion; 6) that an exponential increase of
species could become significant only after attaining a threshold
value at the start of the Cambrian; and, 7) that once
multicellular organisms appeared, the intrinsic possibilities for
variation increased enormously with a resultant explosion of
evolved forms. Unfortunately, there is no evidence to suggest a
selection of one of these proposals, although some of them are
less convincing than others. And of course the truth may be that
more than one factor was involved. No matter the origin, the
Cambrian explosion is apparently accepted by most paleobiologists
as a real discontinuity, a period that saw the sudden emergence
of dozens of new orders and phyla, including sponges, annelids,
crustaceans, hemichordates, brachiopods, and mollusks.
... ... *Precambrian "phylogenetic fuse": The term "fuse" here is
a metaphor for a proposed long series of precursor events leading
to the apparent "explosion" in the fossil record. The essential
question is whether the apparent explosion in the fossil record
was the result of relatively sudden changes in preservation
constraints (e.g., hard-body vs. soft-body forms), or whether a
set of special conditions (e.g., climate change or atmospheric
oxygen availability) provoked an actual rapid diversification of
forms.
... ... *Ediacaran metazoans: The term "Ediacaran" refers to an
assemblage (until recently the oldest) of soft-bodied marine
animals, the assemblage first discovered in the Ediacara Hills in
Australia.
... ... *mitochondrial DNA: Mitochondrial DNA (sometimes denoted
as mtDNA), found in the mitochondria of all eukaryotes, is
believed to evolve in parallel with nuclear DNA, but since sperm
lose their mitochondria, it is inherited only in the maternal
lineage in animals.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 20Nov98
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
6. MATERIALS SCIENCE:
SUPERCONDUCTIVITY: ON 50 YEARS OF THEORY
The current general theory of superconductivity is based on
several ideas:
1) The interaction between particles involves the exchange
of energy quanta.
2) The interaction between electrons in a material can under
certain conditions produce an effective "coupling" between
electrons, and when this occurs, the material may exhibit
superconductivity -- the flow of electrons without resistance.
3) The interaction and effective coupling between electrons
in a material can take various forms, involving various types of
energy quanta, depending on the material and on conditions, and
thus producing the various types of superconductivity.
In this context, a "heavy-fermion" system is one in which
electrons acquire very large effective masses, often hundreds of
times that of a free electron [*Note #1].
... ... Piers Coleman (Rutgers University, US) presents a
commentary on current research in superconductivity, the author
making the following points concerning the history of theory in
this field:
1) In the late 1950s, John Bardeen (1908-1991), Leon N.
Cooper, and John R. Schrieffer demonstrated that
superconductivity involves the formation of bound pairs of
electrons, called "Cooper pairs". Their theory (BCS theory)
argued that the electron pairs were "glued together" by small
deformations (phonons) in the crystal lattice, the deformations
accompanying the motions of electrons. But although phonons had
been implicated in superconductivity many years before BCS
theory, it was not until the 1960s that it became possible to
definitively identify phonons as the "glue" (the interaction
energy quanta) in conventional superconductivity.
2) In the early 1960s, G. Eliashberg demonstrated that the
electron-pairing forces created by phonons could be incorporated
into BCS theory using a set of equations that now bear his name.
It turns out that the exchange of phonons between the electrons
in a Cooper pair produces tiny harmonics in the energy
distributions of the electrons, and these harmonics can be
detected experimentally. In the late 1960s, W.L. McMillan and
J.M. Rowell experimentally confirmed the long-suspected role of
phonons in conventional superconductors, and demonstrated that
the Eliashberg refinement of BCS theory was accurate to
approximately 1 percent.
3) The 1970s and 1980s led to the discovery of
superconductivity in two new unconventional classes of materials,
the heavy-fermion and high-temperature superconductors.
Conventional superconductivity is suppressed by the tiniest
concentration of magnetic atoms, but the unconventional
superconductors contain a dense array of magnetic atoms, which
appear to be actively involved in electron pairing. This has led
physicists to consider a new kind of magnetically mediated
superconductivity in which the quanta that glue electrons into
pairs are derived from magnetic fluctuations. In many kinds of
unconventional superconductors, it appears that the glue that
binds electrons together exists only as a fleeting entity, rather
than as a well-defined excitation.
-----------
Piers Coleman: Magnetic glue exposed.
(Nature 15 Mar 01 410:320)
QY: Piers Coleman: coleman@physics.rutgers.edu
-----------
Text Notes:
... ... *Note #1: Fermions (electrons, protons, neutrons) are
particles that obey the Pauli exclusion principle: i.e., no two
fermions of the same kind can occupy the same quantum state.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 29Jun01
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON THE DISCOVERY OF HIGH TEMPERATURE SUPERCONDUCTIVITY
One of the operating tenets of 20th century "big science" is that
important breakthroughs in science can be more or less engineered
if appropriate conditions are constructed and appropriate
individual researchers placed in those conditions. When this
approach produces a success, the various bureaucrats who support
the idea feel reaffirmed; when various counter-examples to the
approach occur, it is the turn of the doubters to feel
reaffirmed. A cogent instance of a counter-example was provided
in 1986 by the Bednorz-Mueller discovery of high-temperature
superconductivity -- a discovery of signal importance in
experimental physics made by two relatively unknown researchers
working in what can be characterized as a backwater and poorly-
equipped laboratory. Not only was the discovery of high-
temperature superconductivity totally unexpected by the
international physics community, but the discovery of the
phenomenon by outsiders under "little science" conditions caused
a degree of shock in the science policy system. Ordinary
superconductivity is a property of many metals, alloys, and
chemical compounds at temperatures near absolute zero, at which
temperatures (their "critical temperatures") their electrical
resistivity vanishes and they become strongly diamagnetic.
(Diamagnetic substances such as the alkalis and alkaline earth
metals, the halogens, and the noble gases are repelled by magnets
and tend to position themselves at right angles to the magnetic
lines of force.) High-temperature superconductors were unknown
until 1986, but at present there are some known high-temperature
superconductors with critical temperatures greater than 100
kelvins. The accepted theory of ordinary superconductivity
is the Bardeen-Cooper-Schrieffer theory (BCS theory) (1957). At
the present time, a successful theory of high-temperature
superconductivity has not been developed, in spite of a great
deal of effort. Johannes Georg Bednorz (1950- ) and K. Alexander
Mueller (1927- ) shared the Nobel Prize in Physics in 1987 for
their discovery of high-temperature superconductivity in a
ceramic oxide (lanthanum-barium-copper) alloy at 30 kelvins, at
that time the highest superconductivity temperature
ever observed, the work having been carried out at the IBM Zurich
Research Laboratories at Rueschlikon.
... ... Helga Nowotny (Swiss Federal Institute of Technology, CH)
presents an essay on innovation in research and the modern
partnership between basic research and applied science, the
author making the following points:
1) One of the most exciting recent success stories of
science began in September 1986 with the appearance in the
_Zeitschrift fur Physik_ of an article with the cautious title,
"Possible high-T(subc) superconductivity in the Ba-La-Cu-O
system." A few weeks later, the names of the two authors,
Alexander Mueller and Georg Bednorz, and their discovery hit the
front pages of _The New York Times_ and researchers around the
world were caught in an unprecedented frenzy, attempting to
replicate and surpass the findings of the initial breakthrough.
The race for high-temperature superconducting systems was on.
2) The discovery of high-temperature superconductivity was
unexpected in terms of its discoverers, the place of its
discovery, and the scientific ideas involved. It contradicted
conventional wisdom and the expectations of peers and research
administrators. Mueller and Bednorz were outsiders, Mueller a
specialist on perovskites (a type of oxide mineral) and Bednorz a
crystallographer. They benefitted from the novice effect, but
they also enjoyed a degree of autonomy that allowed them to
prepare for the unpredictable. Of the 3 superconductivity
laboratories of IBM, the Rueschlikon laboratory where the two
researchers were based was by far the most modestly equipped. And
the discovery contradicted long-held views, not only overturning
certain established empirical rules concerning superconductivity,
but also unveiling previously unknown phenomena not accounted for
by the classic Bardeen-Cooper-Schrieffer theory.
3) The author points out that even if we knew how to create
conditions under which creativity can flourish, and how to favor
the occurrence of what cannot be planned, the problem remains of
how to turn highly individualistic bursts of scientific
creativity into socially desired techno-scientific outcomes. "For
the most disturbing paradox is this: there has been a relative
decline in the importance of the individual creative act, while
its proliferation is encouraged. Individual scientific creativity
has become a necessary, but no longer sufficient, precondition in
a long, branching sequence of possibilities."
-----------
Helga Nowotny: Innovation machine on the boil.
(Nature 28 Oct 99 401:859)
QY: Helga Nowotny: Swiss Federal Institute of Technology, ETH-
Zentrum, CH-8092 Zurich, CH.
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 3Dec99
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
7. IN FOCUS: WOMEN IN THE EARLY HISTORY OF GENETICS
[Editor's note: William Bateson (1861-1926), who introduced the
term "genetics" into science and who is considered one of the
founders of 20th century research in genetics, had another (and
less well known) aspect to his career, as the following excerpt
demonstrates.]
--------------
"Between 1900 and 1910, when he left Cambridge to become director
of the new John Innes Horticultural Institute in Merton, Surrey,
Bateson coordinated the work of an active group of researchers,
whose goal it was to investigate the validity and complexities of
Mendelian heredity through breeding experiments using a wide
variety of plants and animals. This collaborative effort -- in
which lecturers, postgraduate students, and undergraduates all
worked within the paradigm of Mendelian heredity under Bateson's
direction -- does not fully satisfy the current understanding of
a scientific _school_, for, as L.C. Dunn pointed out, "there had
been collaborators and assistants but seldom a body of students
to develop the field he founded." Yet this was through no fault
of Bateson. His failure to establish a true school in genetics
stemmed from his own insecure institutional position at Cambridge
and the resistance of this ancient institution to embracing a new
scientific discipline. Only in 1908 did Bateson gain a
professorship at Cambridge, but this was in biology rather than
genetics and was a limited-term appointment, for a period of five
years. As contemporaries and historians alike have acknowledged,
however, the group of followers Bateson attracted at Cambridge
amassed a considerable amount of critical evidence after 1902 and
contributed not only new terminology but also basic concepts that
laid the foundations for rapid progress in the preclassical
period of genetics. What has not been generally recognized is
that Bateson's early group consisted primarily of women. Indeed,
of the thirteen Cambridge researchers closely involved in
Bateson's early research program, seven were women associated
with Newnham College. This is particularly interesting because
the situation of women in science at Cambridge at the time was
dire. Having been in the vanguard in opening university education
to women, the women's colleges of Cambridge, Newnham and Girton,
now faced new challenges. Their students had gained access to
science lectures and laboratories in the mid 1870s and had been
granted the right to sit the Natural Sciences Tripos (NST), one
of the Cambridge honors examinations, in 1881. Women acquitted
themselves well in these examinations and by the late 1890s
sought to be granted university degrees. At the end of a year-
long, often acrimonious, discussion of the question, however,
members of the university overwhelmingly rejected this memorial
(petition) in May 1897. Despite this defeat, by the turn of the
century the second generation of university women was beginning
to reap rewards. More women in science aimed to pursue
postgraduate research and sat the more specialized Part 2 Natural
Sciences Tripos examination, generally taken only by those
aspiring to an academic career in science. Because of the hostile
climate at Cambridge, however, few opportunities existed to
enable Cambridge women to engage in postgraduate research.
Bateson's willingness to accept advanced women students into his
program of research, therefore, provided a remarkable opportunity
for women in biology."
-----------
Marsha L. Richmond: "Women in the Early History of Genetics."
(Isis 2001 92:55)
-------------------
[Editor's note: The harsh circumstances of women in science 100
years ago were not restricted to biology. In the early years
of stellar spectroscopy, particularly at the Harvard Astronomical
Observatory in the US, nearly all the data were catalogued and
analyzed by female astronomers, called "computers", who were
trained professional astronomers but forbidden because of their
sex to use the telescopes. It is an irony of the social history
of science that the work of such female astronomers as Henrietta
Swan Leavitt (1868-1928) and Annie Jump Cannon (1863-1941) came
to be of greater significance than the work of many of the male
astronomers who considered these female astronomers to be no more
than menial assistants.]
-------------------
SCIENCE-WEEK http://scienceweek.com 29Jun01
-------------------
Related Background:
IN FOCUS: ON WOMEN IN PHYSICS
"Forty-nine years old; strong-featured face, brooding eyes, a
mass of dark sexy hair she tosses about like a forties movie
vamp, the walk seductive and knowing, the mouth sullen and
grievance-collecting in repose, then surprisingly girlish in
laughter when the eyes fill with a sudden shimmering light. Alma
Norovsky is a theoretical physicist at a university renowned for
its devotion to the life of the mind. Of her colleagues, Alma
says drily: 'They're very theoretical. People are always asking
me how women are treated here. "Women?" I answer. "They're a
theoretical concept."'... Divorced four years from the physicist
husband she married in graduate school, on her own for the first
time in her life, in love with her new independence and happy to
be working here, Alma nevertheless sighs. 'How do you work in
physics, or live among academic liberal men, and not explode all
day long every day? Once in a while I'm able to control myself...
Last year at a conference I was standing with a group of
physicists, all men, and I was introduced to a new member of the
group. He said, "You're the first good-looking physicist I've
ever met." I casually indicated the man standing beside me and
said, "Oh, that's not true. You know Richard here. He's good-
looking, and he's a physicist." They all looked startled, and
then some of them nodded their heads appreciatively. I was proud
of myself then, but usually it's awful. Still. Always. At every
dinner table, in the office, the constant little indications that
you don't really exist. You've got to remind them that you're a
thinking, working being just like themselves all the time. It's
wearing.'"
-----------
Vivian Gornick: _Women in Science: Portraits from a World in
Transition_. (Simon & Schuster, New York 1983)
(Science-Week 15 Oct 99)
-------------------
Related Background:
WOMEN NOW SUBSTANTIAL PORTION OF ALL NEW US CHEMISTS
The latest survey of the American Chemical Society, covering
chemists and chemical engineers who graduated between July 1996
and June 1997, shows the following statistics for new women
graduates (percentage of total graduates who are women):
Chemistry Bachelor's Degree: 48.2%
Chemistry Master's Degree: 46.2%
Chemistry PhD Degree: 31.6
Chemical Engineering Bachelor's Degree: 35.4%
Chemical Engineering Master's Degree: 29.3%
Chemical Engineering PhD Degree: 22.9%
-----------
(Chem. & Eng. News 9 Mar 98)
-------------------
SCIENCE-WEEK http://scienceweek.com 20Mar98
-------------------
Related Background:
M.I.T ACKNOWLEDGES BIAS AGAINST FEMALE SCIENCE PROFESSORS
One would suppose that in science, an enterprise that emphasizes
rationality, the general attitude would be to maximize the
utilization of scientific talent irrespective of gender. But as
in other areas of human endeavor, suppositions are not realities.
In what has been called an extraordinary admission, top officials
at the Massachusetts Institute of Technology, the most
prestigious science and engineering university in the US, have
issued a report acknowledging that female professors at the
institution suffer from pervasive discrimination. The report
concerns discrimination against women in the M.I.T. School of
Science, and documents a pattern of discrimination in areas
including employment, awards, promotions, inclusion in important
committees, and allocation of resources such as laboratory space
and research funds. At the present time, the M.I.T. School of
Science faculty consists of 8 percent women, and this percentage
has remained virtually unchanged for approximately 20 years. In
February 1999, the American Association of University Professors
issued a report indicating that although the percentage of
faculty women in general in the US grew to 34 percent from 23
percent since 1975, the salary gap for male and female professors
actually widened during this period. In the US, women now
comprise a substantial portion of undergraduate science students,
but only a minor portion of science faculties. Concerning gender
discrimination, Charles M. Vest, the president of M.I.T., is
quoted as saying, "I have always believed that contemporary
gender discrimination within universities is part reality and
part perception. True, but I now understand that reality is by
far the greater part of the balance."
-----------
Carey Goldberg: M.I.T. acknowledges bias against female
professors.
(New York Times 23 Mar 98)
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 2Apr99
For more information: http://scienceweek.com/swfr.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
8. FROM THE SCIENCEWEEK ARCHIVE:
EMERGENT BEHAVIOR IN PHYSICS, CHEMISTRY, BIOLOGY:
-------------------------------------------------
THEORETICAL PHYSICS: ON THE THEORY OF EVERYTHING
In a recent issue of SW (11 Feb 00/Report #1; appended below), we
discussed a call by several biologists for a phenomenological
approach to dynamic processes inside biological cells. In this
issue we discuss a similar call by two physicists (one of them,
R.B.L., a Nobel laureate in physics) concerning "emergent
behavior" in physical systems, i.e., behavior apparently not
predictable from first principles but dependent on new principles
emerging only at higher levels of complexity. In both cases, the
essential question is the same: To what extent are reductionist
approaches to phenomena limited, and where limits exist, what is
to be done?
... ... R.B. Laughlin and D. Pines (2 installations, US) present
a provocative commentary on current fundamental theory in
physics, the authors making the following points:
1) The term "Theory of Everything" refers to the ultimate
theory of the Universe, a set of equations capable of describing
all phenomena that have been observed, or that will ever be
observed. It is the modern incarnation of the reductionist idea
of the ancient Greeks, an approach to the natural world that has
been extremely successful and which for many people is the
central paradigm of physics. A special case of this idea is the
general wavefunction equation of nonrelativistic quantum
mechanics, which describes the everyday world in terms of known
quantities: the charge and mass of the electron, the charges and
masses of the atomic nuclei, and Planck's constant. Less
immediate things in the Universe, such as the planet Jupiter,
nuclear fission, the Sun, or the isotopic abundances of elements
in space are not described by this equation, because important
variables such as gravity and nuclear interactions are missing.
But concerning everyday people-scale phenomena, this equation is
for all practical purposes the Theory of Everything for our
everyday world.
2) The authors suggest, however, that examining the Theory
of Everything, it becomes obvious that it is not even remotely a
theory of every thing. We know the equation is correct because it
has been solved accurately for small numbers of particles
(isolated atoms and small molecules) and found to agree in minute
detail with experiment. But it cannot be solved accurately when
the number of particles exceeds approximately 10. The authors
suggest that no computer existing, or that will ever exist, can
break this barrier -- it is a "catastrophe of dimension": If the
amount of computer memory required to represent the quantum
wavefunction of one particle is N, then the amount of computer
memory required to represent the wavefunction of k particles is
N^(k). Although it is possible to perform approximate
calculations for larger systems, and such calculations have in
many cases been valuable, the schemes for approximating are not
first-principles deductions, they are rather art keyed to
experiment. These approximate approaches thus tend to be the
least reliable precisely when reliability is most needed, i.e.,
when experimental information is scarce, the physical behavior
has no precedent, and the key questions have not yet been
identified.
3) A variety of physical phenomena easily observed in the
laboratory (e.g., the *quantum Hall effect, *superfluid helium,
*Josephson effect) permit measurements of exact quantities that
cannot be deduced by direct calculation from the present Theory
of Everything, for exact results cannot be predicted by
approximate calculations. The authors suggest this point is still
not understood by many professional physicists, who find it
easier to believe that a deductive link exists, and has only to
be discovered, than to face the truth that there is no link. But
the absence of a link is true nonetheless, and not denied by the
reliability of such experiments: The important consideration is
that experiments concerning these physical phenomena work because
there are higher organizing principles in nature that make them
work.
4) Concerning Big Bang cosmology and attempts to develop
fundamental theory from considerations and observations of the
early Universe, the authors suggest that no one familiar with
violent high-temperature phenomena would dare to infer anything
about the equations of quantum mechanics by studying explosions,
for explosions are unstable and quite unpredictable from one
experiment to the next. The authors suggest that the assumption
that the early Universe should be exempt from this problem, and
that a Theory of Everything can be inferred from observations of
the early Universe, is not justified by anything except wishful
thinking. It could very well turn out that the Big Bang is the
ultimate emergent phenomenon, "for it is impossible to miss the
similarity between the large-scale structure recently discovered
in the density of galaxies and the structure of styrofoam,
popcorn, or puffed cereals."
5) The authors suggest that the fact that the essential role
played by higher organizing principles in determining emergent
behavior continues to be disavowed by so many physical scientists
is a poignant comment on the nature of modern science. To solid-
state physicists and chemists, who are schooled in quantum
mechanics and deal with it every day in the context of
unpredictable electronic phenomena such as that exhibited by
*Kondo insulators or *cuprate superconductivity, the existence of
these organizing principles in emergent behavior is so obvious
that it is a commonplace not discussed in polite company. But to
other scientists, the idea is considered dangerous and ludicrous,
since it is fundamentally at odds with the reductionist beliefs
central to much of physics. But, the authors suggest, the safety
that comes from acknowledging only the facts one likes is
fundamentally incompatible with science, and sooner or later this
attitude "must be swept away by the forces of history".
6) The authors point out that for the biologist, evolution
and emergence are part of daily life. For many physicists, on the
other hand, the transition from a reductionist approach may not
be easy, but should, in the long run, prove highly satisfying.
Living with emergence means, among other things, focusing on what
experiment tells us about candidate scenarios for the way a given
system might behave before attempting to explore the consequences
of any specific model. This contrasts sharply with the imperative
of reductionism, which requires us never to use experimental
observations in the formulation of theory, as the objective of
reductionism is to construct a deductive path from the ultimate
equations to the experiment without "cheating". But this is
unreasonable when the behavior in question is emergent, for the
higher organizing principles -- the core physical ideas on which
the model is based -- would have to be deduced from the
underlying equations, and in general this is impossible.
Repudiation of this physically unreasonable constraint is the
first step down the road to fundamental discovery.
7) The authors conclude: "The central task of theoretical
physics in our time is no longer to write down the ultimate
equations but rather to catalogue and understand emergent
behavior in its many guises, including potentially life itself.
We call this physics of the next century the study of complex
adaptive matter. For better or worse we are now witnessing a
transition from the science of the past, so intimately linked to
reductionism, to the study of complex adaptive matter, firmly
based in experiment, with its hope for providing a jumping-off
point for new discoveries, new concepts, and new wisdom."
-----------
Editor's note: Contrast with the above views the reports on
complexity in chemistry and biology appended below.
-----------
R.B. Laughlin and D. Pines: The Theory of Everything.
(Proc. Natl. Acad. Sci. US 4 Jan 00 97:28)
QY: R.B. Laughlin, Dept. of Physics, Stanford Univ. 415-723-3058.
-----------
Text Notes:
... ... *quantum Hall effect: In classical physics, the Hall
effect is the development of a transverse voltage across a
current-carrying conductor in a magnetic field, the voltage being
perpendicular to both the direction of the current and the
direction of the magnetic field. In quantum physics, there are
two other Hall effects, an integer charge quantum Hall effect,
and a fractional charge quantum Hall effect, these quantum Hall
effects being observed at extremely low temperatures (a few
kelvins) and extremely intense magnetic fields (at least several
tesla). Both quantum Hall effects were first noted in the 1980s,
and the fractional quantum Hall effect, although experimentally
observed, has not been theoretically resolved. In 1982, R.B.
Laughlin (one of the authors of the paper reviewed in the present
report) postulated the theoretical existence of quasi-particle
excitations with fractional charge e/3, where e is the
conventional electronic charge, the quasi-particle being the
statistical result of the collective motion of many electrons. R.
de-Picciotto et al (1997) apparently demonstrated unambiguously
the existence of quasi-particles with fractional charge as
predicted by Laughlin's theory.
... ... *superfluid helium: In general, a "superfluid" is a fluid
that flows without any resistance. "Superconductivity" is
sometimes considered as a special case of superfluidity in which
the "fluid" components (electrons) are charged. But more
conventionally, superfluidity is considered a property of liquid
helium at extremely low temperatures, a property that enables
liquid helium to flow without friction. Both helium isotopes
(sup4)He (the common isotope, often denoted as helium-4) and
(sup3)He (the rare isotope, often denoted as helium-3) possess
superfluidity under special circumstances.
... ... *Josephson effect: In general, any of the phenomena that
occur at sufficiently low temperatures when a current flows
through a thin insulating layer between two superconducting
substances. Such phenomena were predicted theoretically by B.D.
Josephson in 1962. Josephson was 22 years of age when he made his
theoretical discovery; he received the Nobel Prize in Physics in
1973.
... ... *Kondo insulators: An insulator exhibiting the Kondo
effect. The Kondo effect is a large anomalous increase in the
resistance of certain dilute alloys of magnetic materials in
nonmagnetic hosts as the temperature is lowered. In general, the
Kondo effect occurs when an impurity atom with an unpaired
electron is placed in a metal, producing an interaction of
localized electrons with delocalized electrons.
... ... *cuprate superconductivity: In general, high-temperature
superconductivity exhibited by certain copper alloys. The
accepted theory of ordinary low-temperature superconductivity
is the Bardeen-Cooper-Schrieffer theory (1957). At the present
time, a successful theory of high-temperature superconductivity
has not been developed, in spite of a great deal of effort. J.G.
Bednorz and K.A. Mueller shared the Nobel Prize in Physics in
1987 for their discovery of high-temperature superconductivity in
a ceramic oxide (lanthanum-barium-copper) alloy at 30 kelvins, at
that time the highest superconductivity temperature ever
observed.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 25Feb00
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
ON COMPLEXITY IN CHEMISTRY
The term "complexity" is fashionable in science these days, the
interest presumed to indicate a movement away from reductionism,
away from the idea that the behavior of a system is best
understood in terms of how the components of the system behave
and interact. A focus on "complexity", however, is not perforce
anti-reductionist. Indeed, in practice, with real systems, the
behavior of a system is often not predictable from knowledge of
the behavior of its components, but most often this is simply
because that knowledge is incomplete, and not because of any
_principle_ barring prediction of the behavior of the system from
knowledge of its parts. Even systems exhibiting *chaotic
fluctuations are not necessarily non-reductionist, since such
systems are mathematically deterministic. In any case, faced with
an apparent unpredictability of a system given available
information about its parts, one looks for predictive global
methods to understand the system, methods that do not depend upon
a detailed knowledge of the behavior of the components of the
system. Thermodynamics is exactly such a global method of great
utility in chemistry and physics, and since thermodynamics is a
method of analysis that goes back to its originator Carnot in
1824, one can safely say that the idea of special methods to deal
with "complexity" is quite old. In our time, at least for ideal
systems, we can derive the equations of thermodynamics from
statistical mechanics, i.e., derive the global equations from
equations for the behavior of components. But Nicolas Sadi Carnot
(1796-1832) never heard of statistical mechanics, which was
introduced by Boltzmann (1844-1906) in 1871; Carnot founded
thermodynamics as a predictive global method to deal with an
important "complex" system of his time -- the steam engine.
... ... G.M. Whitesides and R.F. Ismagilov (Harvard University,
US) present a review of current ideas in chemistry concerning
"complexity", the authors making the following points:
1) Chemistry has its own understandings of the term
"complexity". In one characterization, a complex system is one
whose evolution is very sensitive to initial conditions or to
small perturbations, one in which the number of independent
interacting components is large, or one in which there are
multiple pathways by which the system can evolve. Analytical
descriptions of such systems typically require nonlinear
differential equations. A second characterization is more
informal; that is, the system is "complicated" by some subjective
judgment and is not amenable to exact description, analytical or
otherwise.
2) Faced with the impossibility of handling many real
systems exactly, chemists have evolved a series of approaches to
the treatment of complex systems. These treatments include
reasoning by analogy, averaging, linearization, drastic
approximation, pure empiricism, and detailed analytical solution.
The emphasis in thinking about complicated systems has been to
find methods that are predictive, even if they are non-
analytical. "Complexity" per se, the study of nonlinear processes
with high sensitivity to conditions, has not been the focus of
major effort.
3) Chemistry has relied heavily on the ability of ensemble
properties that are obtained through thermodynamics and
statistical mechanics to make it unnecessary to consider the
behavior of individual molecules. However, single-molecule
chemistry is now making it possible to inquire about individual
molecular behaviors, and the behavior of macromolecules is a
promising area of research because of the existence of many
possible molecular conformations, each with different properties.
4) At the core of chemical interest in complexity are the
two fundamental problems concerning life: a) how collections of
molecules give rise to the varieties of behaviors that
characterize cells and organisms; and 2) how individual molecules
might have originally assembled into collections that had the
characteristics of life (energy dissipation, self-replication,
and adaptation). Whether the understanding of complexity at the
molecular level will reveal important elements of the structure
of life is unclear.
5) One of the opportunities in fundamental chemical research
is to learn from biology and to use what is learned to design
non-biological systems that dissipate energy, replicate, and
adapt. Whether such systems would model life is not critical;
they would unquestionably be interesting and probably important.
-----------
G.M. Whitesides and R.F. Ismagilov: Complexity in chemistry.
(Science 2 Apr 99 284:89)
QY: George M. Whitesides: gwhitesides@gmwgroup.harvard.edu
-----------
Text Notes:
... ... *chaotic fluctuations: The term "chaotic", in this
context, is specific. In the study of physical systems, the
term "chaotic behavior" has a specific meaning: the behavior of a
system is said to be "chaotic" if its final state is so sensitive
to the system's precise initial conditions that the behavior of
the system is in effect unpredictable and cannot be distinguished
from a random process, even though the behavior of the system is
strictly determinate in a mathematical sense. In other words, a
deterministic system characterized by extremely sensitive
instabilities, despite the system being determinate, can exhibit
behavior that is unpredictable, and the system is then called
"chaotic". During the past several decades, the analysis of such
chaotic systems has intrigued both physicists and mathematicians.
-------------------
Summary & Notes by SCIENCE-WEEK http://scienceweek.com 2Jul99
For more information: http://scienceweek.com/swfr.htm
-------------------
Related Background:
CELL BIOLOGY: FUNCTIONAL MODULES IN BIOLOGICAL ORGANIZATION
The term "phenomenology" has a variety of meanings, but in
this report we are concerned with only one meaning of the term:
we take the term "phenomenology" to refer to a scientific
approach that focuses on explanations based on formal
relationships among observed entities or processes, as opposed to
an approach ("reductionist") that focuses on explanations based
on analysis of the fundamental constituents of such entities or
processes. Using the terms in this way, we have the following
examples: a) Thermodynamics is a phenomenological approach to the
behavior of a gas; statistical mechanics is a reductionist
approach to the behavior of a gas. b) Mendelian genetics is a
phenomenological approach to the inheritance of traits; molecular
genetics is a reductionist approach to the inheritance of traits.
One can think of similar dichotomies in almost every field in
science.
The term "reductionist" has had an unfortunate history in
biology, where it has been used to characterize the idea that any
biological entity or process can be "explained" in terms of the
laws of physics and chemistry. Certainly, the behavior of every
entity or process in the natural world is ultimately totally
dependent on the laws of physics and chemistry (which leads to
the idea that the behavior can "in principle" be derived
["explained"] from such laws), but the actual practical
possibility of any explanations of the behavior of observable
entities or processes in terms of the laws of physics and
chemistry depends on the current state of our knowledge
concerning both the observables and the fundamental laws. In the
practice of science, it can be argued that it does not matter
much which approach is used, phenomenological or reductionist,
provided the approach produces results that are useful, or which
help in understanding the behavior of the entity or process, or
which suggest new and intriguing questions. Beyond this, the
discussion properly belongs in the domain of philosophy and not
science.
The above preamble is necessary in the context of the
present report, since the report concerns a recent article in
which a group of authors (2 molecular biologists, a biophysicist,
and a physiologist) call for a more "phenomenological" approach
to cell biology, an interesting idea, since cell biology is not
one of those areas of biology where such appeals are common.
During the last 50 years, in fact, cell biology has experienced a
remarkable flowering based on the application of fundamental
biochemistry, biophysics, and molecular biology to entities and
processes recognizable at the cellular level (i.e., micron-scale
objects).
... ... L.H. Hartwell et al (4 authors at 3 installations, US)
present an essay calling for a transition from molecular to
"modular" cell biology, the authors making the following points:
1) The authors begin their essay with the following
statement: "Although living systems obey the laws of physics and
chemistry, the notion of function or purpose differentiates
biology from other natural sciences. Organisms exist to
reproduce, whereas, outside religious belief, rocks and stars
have no purpose. Selection for function has produced the living
cell, with a unique set of properties that distinguish it from
inanimate systems of interacting molecules." [Editor's note:
Contrast with this the remarks in the relevant background
material below.]
2) The authors propose that a major challenge for science in
the 21st century is to develop an integrated understanding of how
biological cells and organisms survive and reproduce. The authors
suggest that cell biology is in transition from a science that
was preoccupied with assigning functions to individual proteins
or genes, to a science that is now attempting to cope with the
complex sets of molecules that interact to form "functional
modules".
3) The authors define a "functional module" as a discrete
entity whose function is separable from those of other modules.
This separation depends on chemical isolation, which can
originate from spatial localization or from chemical specificity.
For example, a ribosome, the module that synthesizes proteins,
concentrates the reactions involved in making a polypeptide into
a single particle, thus spatially isolating its function. Modules
can be insulated from or connected to each other. The authors
suggest that in the future, the higher-level properties of cells,
such as their ability to integrate information from multiple
sources, will be described by the pattern of connections among
their functional modules.
4) The authors point out that the number of cellular
functional modules that have been analyzed in detail is very
small, and each of these efforts has required intensive study.
The authors suggest that biologists need to study more functions
at the modular level and develop methods that make it easier to
determine the relationship of inputs to outputs of modules, their
biochemical connectivity, and the states of key intermediates
within them.
5) The authors suggest that the best test of our
understanding of cells will be to make quantitative predictions
about their behavior and test them. This will require detailed
simulations of the biochemical processes occurring within the
modules. "But making predictions is not synonymous with
understanding. We need to develop simplifying, higher-level
models and find general principles that will allow us to grasp
and manipulate the functions of biological modules."
6) The authors summarize their essay: "Cellular functions,
such as signal transmission, are carried out by 'modules' made up
of many species of interacting molecules. Understanding how
modules work has depended on combining phenomenological analysis
with molecular studies. General principles that govern the
structure and behavior of modules may be discovered with help
from synthetic sciences such as engineering and computer science,
from stronger interactions between experiment and theory in cell
biology, and from an appreciation of evolutionary constraints."
-----------
[Editor's note: The essential idea here can be presented as
follows: Consider a computer, a machine with a "purpose" -- to
compute. A computer operates on its inputs in specific ways to
produce specific outputs. A "flow diagram" of computer dynamics
is a phenomenological description of the behavior of the machine.
A complete "wiring diagram" of electrical entities and events in
the machine is a reductionist description of the behavior of the
machine. (Of course, from the perspective of quantum mechanics,
the wiring diagram is itself phenomenological.) Suppose we are
given a machine and know nothing about it except that it operates
on inputs to produce outputs. If our problem is to predict the
behavior of the machine in response to particular inputs, there
will come a time when a flow diagram, albeit "phenomenological",
will be of immense value in understanding how the machine works.
What the authors propose is that much of the future of cell
biology will lie in the construction of the equivalent of
detailed and predictive flow diagrams for the internal operations
of biological cells.]
-----------
L.H. Hartwell: From molecular to modular cell biology.
(Nature 2 Dec 99 402supp:C47)
QY: Leland H. Hartwell, Fred Hutchinson Cancer Center, Seattle,
WA 98109 US.
-------------------
Summary by SCIENCE-WEEK http://scienceweek.com 11Feb00
-------------------
Related Background:
IN FOCUS: ON FUNCTION AND TELEOLOGY IN BIOLOGY
"Biology, and especially evolutionary biology, is rife with
claims concerning what various characteristics are "for". The
heart exists for the purpose of pumping blood. Bears have fur in
order to ward off the cold. Functional claims of this sort have
quite disappeared from physics. Whereas Aristotle thought that
planets, no less than living things, have goals, this
teleological conception of the physical world is now a relic of a
bygone age. Planets move as they do because of the laws of
motion; they do not act as they do for the good of anything.
Darwin is rightly famous for having introduced an important
materialist element into the science of life. But rather than
banishing functional notions from biology, he showed how they can
be domesticated within a materialist framework. Organisms are
goal-directed systems because they have evolved. Their behaviors
are suited to the tasks of survival and reproduction because
natural selection has allowed some traits, but not others, to be
passed from ancestors to descendants. Even if Darwinism
legitimates talk of goal and purpose within biology, the question
of what such talk means remains to be addressed. The heart does
many things. It pumps blood, but it also makes noise and takes up
space in our chests. Why are we inclined to say that pumping
blood is part of the heart's function, but making noise and
taking up space are not?"
-----------
Elliott Sober (ed.): _Conceptual Issues in Evolutionary Biology_
(MIT Press, Cambridge MA 1995, p.x)
(Science-Week 9 Jul 99)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
NOTICES
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
ScienceWeek invites explicative commentaries on research, theory,
science policy, etc. For details, please see:
http://www.scienceweek.com/authors.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
CHANGE OF EMAIL ADDRESS:
If at any time you need to change the Email address at which you
receive SW, please send the information to:
request@scienceweek.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
SCIENCE-WEEK SUBSCRIPTIONS:
Complete subscription information is available at:
http://scienceweek.com/subinfo.htm
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
The first issue of ScienceWeek appeared May 1, 1997, and it has
been published regularly each week since that date. Content is
designed to cross existing conceptual and linguistic barriers
between the scientific disciplines: reports in the physical
sciences are presented primarily for biological scientists, and
reports in the biological sciences are presented primarily for
physical scientists. The SW website contains thousands of reports
from back issues, plus a concordance search engine for all
content in the back issue archive. Access to the website is free.
We welcome comments, suggestions, and criticisms from our
subscribers. Public letters relevant to any report are also
welcome. Editorial contact: editors@scienceweek.com
Editor/Publisher: Dan Agin
Managing Editor: Claire Haller
Associate Editor: Joan Oliner
Copyright (c) 1997-2001 SCIENCE-WEEK/Spectrum Press Inc.
All Rights Reserved
US Library of Congress ISSN 1529-1472
---------------------------------------------
ScienceWeek has a liberal copying policy.
For information about copying, see the following:
http://www.scienceweek.com/copying.htm
ScienceWeek is published by Spectrum Press Inc.,
3023 N. Clark Street #109, Chicago, 60657-5205 IL, USA.
---------------------------------------------
-----end file
|