Download ScienceWeek - Kabbalah.info

http://scienceweek.com/2004/sa041231-2.htm
ScienceWeek
EVOLUTION OF BEHAVIOR: ON COLLECTIVE ACTION IN LARGE GROUPS
The following points are made by Ernst Fehr (Nature 2004 432:449):
1) War is a prime example of large-scale within-group cooperation between genetically
unrelated individuals. War also illustrates the fact that within-group cooperation often
serves the purpose of between-group aggression. Modern states are able to enforce
cooperation in large groups by means of sophisticated institutions that punish individuals
who refuse to meet their duties and reward those who follow their superiors' commands.
The existence of such cooperation-enhancing institutions is very puzzling from an
evolutionary viewpoint, however, because no other species seems to have succeeded in
establishing large-scale cooperation among genetically unrelated strangers(1).
2) The puzzle behind this cooperation can be summarized as follows. Institutions that
enhance within-group cooperation typically benefit all group members. The effect of a
single group member on the institution's success is negligible, but the contribution cost is
not negligible for the individual. Why, therefore, should a self-interested individual pay the
cost of sustaining cooperative institutions? More generally, why should a self-interested
individual contribute anything to a public good that -- once it exists -- an individual can
consume regardless of whether he contributed or not? Recent work(2) advances the scope
of reputation-based models(3-5) and demonstrates that individuals' concern for their
reputation may be a solution to this puzzle.
3) Evolutionary psychologists have sought to answer the puzzle of human collective action
for decades. However, progress was limited because of a lack of commitment to
mathematically rigorous theorizing. Many researchers erroneously thought that the notion
of reciprocal altruism, formalized as a tit-for-tat strategy for two-person interactions,
provides the solution to the problem. It was speculated that reciprocal altruism "may favor
a multiparty altruistic system in which altruistic acts are dispensed freely among more
than two individuals". However, it is always easier to speculate than to provide a rigorous
model, and the speculation is likely to be wrong in this case.
4) In the context of the problem of public-goods provision, a reciprocally altruistic
individual is willing to contribute to the public good if sufficient numbers of other group
members are also willing to contribute. Unfortunately, the presence of only a small number
of defectors quickly causes cooperation to unravel if it is solely based on conditionally
cooperative behavior, because the defectors induce the conditional cooperators to defect as
well. Theory and simulations suggest that reciprocally altruistic strategies can only sustain
high levels of cooperation in two-person interactions. Moreover, experimental evidence
indicates that cooperation in public-good games typically unravels because it is not possible
to discipline "free riders" -- those who take advantage of others' cooperation -- if only
conditionally cooperative strategies are available.
References (abridged):
1. Fehr, E. & Fischbacher, U. Nature 425, 785-791 (2003)
2. Panchanathan, K. & Boyd, R. Nature 432, 499-502 (2004)
3. Nowak, M. A. & Sigmund, K. Nature 393, 573-577 (1998)
4. Leimar, O. & Hammerstein, P. Proc. R. Soc. Lond. B 268, 745-753 (2001)
5. Gintis, H., Smith, E. A. & Bowles, S. J. Theor. Biol. 213, 103-119 (2001)
Nature http://www.nature.com/nature
-------------------------------Related Material:
ON NATURAL SELECTION, KIN SELECTION, AND ALTRUISM
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.
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.
-------------------------------Related Material:
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. 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.
2) 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.
ScienceWeek http://scienceweek.com