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ScienceWeek
ANIMAL BEHAVIOR: ON COOPERATION AMONG CHIMPANZEES
The following points are made by Joan B. Silk (Science 2006 311:1248):
1) Evolutionary theory predicts that altruistic interactions, which are costly to the actor and beneficial to the recipient, will be limited to kin or reciprocating partners. This precludes anonymous acts of altruism on behalf of strangers, such as giving blood, or large-scale cooperation, such as serving on committees. Cooperation is equally perplexing to economists whose theorems are based on the principle of maximizing profit and self-interest, not concern for the welfare of others. Evolutionary theory and economic models provide a comfortable fit for the behavior of other animals [1-5], including other highly social and intelligent members of the primate order, but humans stand out as a puzzling anomaly [1].
2) This raises two questions: Why do humans cooperate so much? And what limits the extent of cooperation in other animals? While evolutionary social scientists struggle with the first question, primatologists are beginning to tackle the second. Much of this work focuses on chimpanzees. Chimpanzees participate in a variety of collective activities in the wild, but we can't say much about the motives underlying cooperation or the factors that prevent them from cooperating more in the wild. So researchers have headed into the laboratory to probe the capacity and motivation for cooperation.
3) To cooperate effectively, individuals must know what needs to be done and be willing to do it. Experimental efforts to induce nonhuman primates (capuchins, tamarins, and chimpanzees) to work together in joint tasks have met with mixed success. But it is not clear whether collaborative failures occurred because animals didn't understand how to solve the tasks or because they were inhibited by the presence of competitors who monopolized the apparatus and appropriated rewards.
4) Two sets of experiments conducted by researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany [2] provide compelling evidence that chimpanzees collaborate effectively under appropriate conditions. In one set of experiments, bowls of food were attached to a platform outside the testing room. A rope was threaded through the platform so that it could be pulled forward only if two chimpanzees pulled on the ends of the rope at the same time. Pairs of chimpanzees that got along well in other settings quickly learned to solve this task together, but chimpanzees paired with less preferred partners were much less successful. The same apparatus was used in another set of experiments [2], but with one chimpanzee placed in the testing room and the other in an adjoining room. The chimpanzee in the testing room could admit the other by removing a key that locked the door between the two rooms. First, Melis and her colleagues manipulated the need for collaboration by varying the distance between the ends of the rope threaded through the platform. A chimp was more likely to recruit an assistant when the rope ends were too far apart to be pulled at the same time by one individual. Second, the chimps were allowed to choose between two potential collaborators who differed in their effectiveness in the task. Initially, the chimpanzees did not discriminate between the two assistants, but they came to show a strong preference for the more effective helper.
References (abridged):
1. E. Fehr, U. Fischbacher, Nature 425, 785 (2003)
2. A. P. Melis, B. Hare, M. Tomasello, Science 311, 1297 (2006)
3. F. Warneken, M. Tomasello, Science 311, 1301 (2006)
4. S. T. Emlen, in Behavioural Ecology: An Evolutionary Approach, J. R. Krebs, N. B. Davies, Eds. (Blackwell Scientific, Oxford, 1997), pp. 228-253
5. L. A. Dugatkin, Cooperation Among Animals (Oxford Univ. Press, Oxford, 1997)
Science http://www.sciencemag.org
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SOCIO-ECONOMIC SCIENCE: ON HUMAN ALTRUISM
The following points are made by E. Fehr and U. Fischbacher (Nature 2003 425:785):
1) Human societies represent a huge anomaly in the animal world(1). They are based on a detailed division of labor and cooperation between genetically unrelated individuals in large groups. This is obviously true for modern societies with their large organizations and nation states, but it also holds for hunter-gatherers, who typically have dense networks of exchange relations and practise sophisticated forms of food-sharing, cooperative hunting, and collective warfare(2,3). In contrast, most animal species exhibit little division of labor and cooperation is limited to small groups. Even in other primate societies, cooperation is orders of magnitude less developed than it is among humans, despite the close common ancestry of primates and humans. Exceptions are social insects such as ants and bees, or the naked mole rat; however, cooperation in these species is based on a substantial amount of genetic relatedness.
2) Why are humans so unusual among animals in this respect? The authors propose that quantitatively, and probably even qualitatively, unique patterns of human altruism provide the answer to this question. Human altruism goes far beyond that which has been observed in the animal world. Among animals, fitness-reducing acts that confer fitness benefits on other individuals are largely restricted to kin groups; despite several decades of research, evidence for reciprocal altruism in pair-wise repeated encounters(4,5) remains scarce. Likewise, there is little evidence so far that individual reputation building affects cooperation in animals, which contrasts strongly with what we find in humans. If we randomly pick two human strangers from a modern society and give them the chance to engage in repeated anonymous exchanges in a laboratory experiment, there is a high probability that reciprocally altruistic behavior will emerge spontaneously.
3) However, human altruism extends far beyond reciprocal altruism and reputation-based cooperation, taking the form of strong reciprocity. Strong reciprocity is a combination of altruistic rewarding, which is a predisposition to reward others for cooperative, norm-abiding behaviors, and altruistic punishment, which is a propensity to impose sanctions on others for norm violations. "Strong reciprocators" bear the cost of rewarding or punishing even if they gain no individual economic benefit whatsoever from their acts. In contrast, "reciprocal altruists", as they have been defined in the biological literature(4,5), reward and punish only if this is in their long-term self-interest. Strong reciprocity thus constitutes a powerful incentive for cooperation even in non-repeated interactions and when reputation gains are absent, because strong reciprocators will reward those who cooperate and punish those who defect.
4) In summary: Some of the most fundamental questions concerning our evolutionary origins, our social relations, and the organization of society are centered around issues of altruism and selfishness. Experimental evidence indicates that human altruism is a powerful force and is unique in the animal world. However, there is much individual heterogeneity and the interaction between altruists and selfish individuals is vital to human cooperation. Depending on the environment, a minority of altruists can force a majority of selfish individuals to cooperate or, conversely, a few egoists can induce a large number of altruists to defect. Current gene-based evolutionary theories cannot explain important patterns of human altruism, pointing towards the importance of both theories of cultural evolution as well as theories of gene culture co-evolution.
References (abridged):
1. Boyd, R. & Richerson, P. The Nature of Cultures (Univ. Chicago Press, Chicago, in the press)
2. Kaplan, H., Hill, J., Lancaster, J. & Hurtado, A. M. A theory of human life history evolution: diet, intelligence, and longevity. Evol. Anthropol. 9, 156-185 (2000)
3. Hill, K. Altruistic cooperation during foraging by the Ache, and the evolved human predisposition to cooperate. Hum. Nat. 13, 105-128 (2002)
4. Trivers, R. L. Evolution of reciprocal altruism. Q. Rev. Biol. 46, 35-57 (1971)
5. Axelrod, R. & Hamilton, W. D. The evolution of cooperation. Science 211, 1390-1396 (1981)
Nature http://www.nature.com/nature
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Notes by ScienceWeek:
In this context, the term "altruism" refers in general to behavior that benefits another individual, usually of the same species, at the expense of the agent. The phenomenon is widespread among various species, and has been interpreted by some as apparently at odds with Darwinian theory. Theories of altruism in biology are often concerned with "cost-benefit" analysis as dictated by the logic of natural selection.
The term "Hamilton's rule" refers to the prediction that genetically determined behavior that benefits another organism, but at some cost to the agent responsible, will spread by natural selection when the relation (rb-c} > 0 is satisfied, where (r) is the degree of relatedness between agent and recipient, (b) is the improvement of individual fitness of the recipient caused by the behavior, and (c) is the cost of the agent's individual fitness as a result of the behavior. The rule was first proposed by William D. Hamilton (1936-2000), and Hamilton's theory is often referred to as "kin selection". As an example: A mutation that affected the behavior of a sterile worker bee so that she fed her fertile queen but starved herself would increase the inclusive fitness of that worker because, while her own fitness decreased, her actions increased the fitness of a close relative.
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ON NATURAL SELECTION, KIN SELECTION, AND ALTRUISM
The following points are made by Mark Ridley (citation below):
1) Natural selection working on groups of close genetic relatives is called kin selection. In species in which individuals sometimes meet one another, such as in social groups, individuals may be able to influence each other's reproduction. Biologists call a behavior pattern altruistic if it increases the number of offspring produced by the recipient and decreases that of the altruist. (Notice that the term in biology, unlike in human action, implies nothing about the altruist's intentions: it is a motive-free account of reproductive consequences.) Can natural selection ever favor altruistic actions that decrease the reproduction of the actor? If we take a strictly organismic view of natural selection, it would seem to be impossible. Yet, as a growing list of natural observations records, animals behave in an apparently altruistic manner. The altruism of the sterile 'workers' in such insects as ants and bees is one undoubted example. In such cases, the altruism is extreme, as the workers do not reproduce in some species.
2) Altruistic behavior often takes place between genetic relatives, where it is most likely explained by the theory of kin selection. Let us suppose for simplicity that we have two types of organism, altruistic and selfish. A hypothetical example might be that, when someone is drowning, an altruist would jump in and try and save him or her, whereas the selfish individual would not. The altruistic act decreases the altruist's chance of survival by some amount which we call c (for cost), because the altruist runs some risk of drowning. The action increases the chance of survival of the recipient by an amount b (for benefit). If the altruists dispensed their aid indiscriminately to other individuals, benefits will be received by other altruists and by selfish individuals in the same proportion as they exist in the population. Natural selection will then favor the selfish types, because they receive the benefits but do not pay the costs.
3) For altruism to evolve, it must be directed preferentially to other altruists. Suppose that acts of altruism were initially given only to other altruists. In such a case, what would be the condition for natural selection to favor altruism? The answer is that the altruism must take place only in circumstances in which the benefit to the recipient exceeds the cost to the altruist. This relation will hold true if the altruist is a better swimmer than the recipient, but it does not logically have to be true (if, for instance, the altruist were a poor swimmer and the recipients were capable of looking after themselves, the net result of the altruist's heroic plunge into the water might merely be that the altruist would drown). If the recipient's benefit exceeds the altruist's cost, then a net increase occurs in the average fitness of the altruistic types as a whole. This condition has only theoretical interest. In practice, it is usually (maybe always) impossible for altruism to be directed only to other altruists, because they cannot be recognized with certainty. It may be possible, however, for altruism to be directed at a class of individuals that contains a disproportionate number of altruists relative to their frequency in the population. For example, altruism may be directed toward genetic relatives. In this case, if a gene for altruism appears in an individual, it is also likely to be in its relatives.
Adapted from: Mark Ridley: Evolution. 2nd Edition. Blackwell Science 1996, p.321.
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