ScienceWeek

ANTHROPOLOGY: ORIGIN OF CLOTHING: MOLECULAR EVIDENCE

The following points are made by R. Kittler et al (Current Biology 2003 13:1414):

1) The human head louse (Pediculus humanus capitis) and body louse (P. humanus corporis or P. h. humanus) are strict, obligate human ectoparasites that differ mainly in their habitat on the host: the head louse lives and feeds exclusively on the scalp, whereas the body louse feeds on the body but lives in clothing. This ecological differentiation probably arose when humans adopted frequent use of clothing, an important event in human evolution for which there is no direct archaeological evidence.

2) The authors used a molecular clock approach to date the origin of body lice, assuming that this should correspond with the frequent use of clothing. Sequences were obtained from two mtDNA and two nuclear DNA segments from a global sample of 40 head and body lice, and from a chimpanzee louse to use as an outgroup.

3) The results indicate greater diversity in African than non-African lice, suggesting an African origin of human lice. A molecular clock analysis indicates that body lice originated not more than about 72,000 +- 42,000 years ago; the mtDNA sequences also indicate a demographic expansion of body lice that correlates with the spread of modern humans out of Africa. The authors suggest these results indicate that clothing was a surprisingly recent innovation in human evolution.

4) The authors point out that a critical assumption is that the origin of body lice reflects the origin of clothing; it is possible that clothing existed for some time before lice exploited this new ecological niche, in which case the origin of clothing could be much more ancient than the origin of body lice. While the authors cannot exclude this possibility, the colonization of a new ecological niche usually occurs rapidly after it becomes available. Since modern humans and archaic humans such as Neandertals diverged approximately 250,000 to 500,000 years ago, in order to associate clothing with archaic humans, clothing would have had to exist for hundreds of thousands of years before the origin of body lice, which seems improbable. Moreover, archaeological evidence does not contradict an association of clothing specifically with modern humans, as the only tools that can be definitely associated with clothing, such as needles, are only approximately 40,000 years old. Earlier tools, such as scrapers, may have been used to prepare hides for clothing, but may also have been used to scrape flesh for food or some other purpose. Indeed, clothing may have allowed early modern humans to colonize more extreme latitudes than their archaic predecessors, and hence might have been a factor in the successful spread of modern humans out of Africa.

Current Biology http://www.current-biology.com

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ANTHROPOLOGY: NEW EVIDENCE FOR OUT OF AFRICA MODEL

The following points are made by Chris Stringer (Nature 2003 423:692):

1) The idea that modern humans originated in Africa, with populations subsequently spreading outwards from there, has continued to gain support lately. But much of that support has come from analyses of genetic variation in people today, and from fossil and archaeological discoveries dated to within the past 120,000 years -- after our species evolved. Hard evidence for the inferred African origin of modern humans has remained somewhat elusive, with relevant material being fragmentary, morphologically ambiguous, or uncertainly dated. Thus the fossilized partial skulls from Ethiopia recently described by White et al (Nature 2003 423:742) are probably some of the most significant discoveries of early Homo sapiens so far, owing to their completeness and well-established antiquity of approximately 160,000 years.

2) There are two broad theories about the origins of H. sapiens. A few researchers still support a version of the "multiregional" hypothesis, arguing that the anatomical features of modern humans arose in geographically widespread hominid populations throughout the Pleistocene epoch (which lasted from around 1.8 million to some 12,000 years ago). But most researchers now espouse a version of the "out of Africa" model, although there are differences of opinion over the complexity of the processes of origin and dispersal, and over the amount of mixing that might subsequently have occurred with archaic (non-modern) humans outside of Africa. Within Africa, uncertainties still surround the mode of modern human evolution -- whether it proceeded in a gradual and steady manner or in fits and starts (punctuational evolution). Other questions concern the relationship between genetic, morphological and behavioral changes, and the precise region, or regions, of origin.

3) For instance, possible early H. sapiens fossils, dating from about 260,000 to 130,000 years ago, are scattered across Africa at sites such as Florisbad (South Africa), Ngaloba (Tanzania), Eliye Springs and Guomde (Kenya), Omo Kibish (Ethiopia), Singa (Sudan) and Jebel Irhoud (Morocco). But the best dated of these finds, from Florisbad and Singa, are problematic because of incompleteness and, in the latter case, evidence of disease. Meanwhile, the more complete or diagnostically modern specimens suffer from chronological uncertainties. So the most securely dated and complete early fossils that unequivocally share an anatomical pattern with today's H. sapiens are actually from Israel, rather than Africa. These are the partial skeletons from Skhul and Qafzeh, dating from around 115,000 years ago. Their presence in the Levant is usually explained by a range expansion from ancestral African populations, such as those sampled at Omo Kibish or Jebel Irhoud around 125,000 years ago.

4) The new cranial material from Herto, Ethiopia -- described by White et al -- adds significantly to our understanding of early H. sapiens evolution in Africa. The fossils are complete enough to show a suite of modern human characters, and are well constrained by argon-isotope dating to about 160,000 years ago. Three individuals are represented by separate fossils: a nearly complete adult cranium (skull parts excluding the lower jaw), a less complete juvenile cranium, and some robust cranial fragments from another adult. All display evidence of human modification, such as cut marks, considered to represent mortuary practices rather than cannibalism. Associated layers of sediment produced evidence of the butchery of large mammals such as hippopotamuses and bovines, as well as assemblages of artefacts showing an interesting combination of Middle Stone Age and late Acheulean technology.

Nature http://www.nature.com/nature

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