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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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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.

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. More information at: http://www.amazon.com/exec/obidos/ASIN/0632043849/scienceweek

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ON ALTRUISM OF INDIVIDUALS IN INSECT SOCIETIES

The following points are made by Edward O. Wilson (citation below):

1) Altruism is self-destructive behavior performed for the benefit of others. The use of the word altruism in biology has been faulted by Williams and Williams (1957), who suggest that the alternative expression "social donorism" is preferable because it has less gratuitous emotional flavor. Even so, altruism has been used as a term in connection with evolutionary argumentation by Haldane (1932) and rigorous genetic theory by Hamilton (1964), and it has the great advantage of being instantly familiar. The self-destruction can range in intensity all the way from total bodily sacrifice to a slight diminishment of reproductive powers.

2) Altruistic behavior is of course commonplace in the responses of parents toward their young. It is far less frequent, and for our purposes much more interesting, when displayed by young toward their parents or by individuals toward siblings or other, more distantly related members of the same species. Altruism is a subject of importance in evolution theory because it implies the existence of group selection, and its extreme development in the social insects is therefore of more than ordinary interest. The great scope and variety of the phenomenon in the social insects is best indicated by citing a few concrete examples:

a) The soldier caste of most species of termites and ants is virtually limited in function to colony defense. Soldiers are often slow to respond to stimuli that arouse the rest of the colony, but, when they do, they normally place themselves in the position of maximum danger. When nest walls of higher termites such as Nasutitermes are broken open, for example, the white, defenseless nymphs and workers rush inward toward the concealed depths of the nest, while the soldiers press outward and mill aggressively on the outside of the nest. Nutting (personal communication) witnessed soldiers of Amitermes emersoni in Arizona emerge from the nest well in advance of the nuptial flights, wander widely around the nest vicinity, and effectively tie up in combat all foraging ants that could have endangered the emerging winged reproductives.

b) I have observed that injured workers of the fire ant Solenopsis saevissima leave the nest more readily and are more aggressive on the average than their uninjured sisters. Dying workers of the harvesting ant Pogonomyrmex badius tend to leave the nest altogether. Both effects may be no more than meaningless epiphenomena, but it is also likely that the responses are altruistic. To be specific, injured workers are useless for most functions other than defense, while dying workers pose a sanitary problem.

c) Alarm communication, which is employed in one form or other throughout the higher social groups, has the effect of drawing workers toward sources of danger while protecting the queens, the brood, and the unmated sexual forms.

d) Honeybee workers possess barbed stings that tend to remain embedded when the insects pull away from their victims, causing part of their viscera to be torn out and the bees to be fatally injured. A similar defensive maneuver occurs in many polybiine wasps, including Synoeca surinama and at least some species of Polybia and Stelopolybia and the ant Pogonomyrmex badius. The fearsome reputation of social bees and wasps in comparison with other insects is due to their general readiness to throw their lives away upon slight provocation.

e) When fed exclusively on sugar water, honeybee workers can still raise larvae -- but only by metabolizing and donating their own tissue proteins. That this donation to their sisters actually shortens their own lives is indicated by the finding of de Groot (1953) that longevity in workers is a function of protein intake.

f) Female workers of most social insects curtail their own egg laying in the presence of a queen, either through submissive behavior or through biochemical inhibition. The workers of many ant and stingless bee species lay special trophic eggs that are fed principally to the larvae and queen.

g) The "communal stomach", or distensible crop, together with a specially modified proventriculus, forms a complex storage and pumping system that functions in the exchange of liquid food among members of the same colony in the higher ants. In both honeybees and ants, newly fed workers often press offerings of ingluvial food on nestmates without being begged, and they may go so far as to expend their supply to a level below the colony average.

3) These diverse physiological and behavioral responses are difficult to interpret in any way except as altruistic adaptations that have evolved through the agency of natural selection operating at the colony level. The list by no means exhausts the phenomena that could be placed in the same category.

Adapted from: Edward O. Wilson: The Insect Societies. Harvard University Press 1971, p.321.

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