Animal Behavior/Sociality< Animal Behavior
Cooperation, Altruism, and SocialityEdit
Many animals and humans show a startling flair for exhibiting kindness, cooperation, and altruistic behavior. Evolution, which is often (and falsely) viewed as largely driven by conflict between competing individuals, may not be an obvious candidates for explaining their existence. Evolution may promote traits underlying group living, altruism, and coorperative behaviors under specific conditions, however, if genes underlying such characteristics are favored. There are several degrees of working together:
- Cooperation refers to the practice of individuals working together instead of working separately in competition. The success of participating individuals depends and is contingent upon the success of their partners in cooperation.
- Altruism consists of unselfish/selfless acts in which the altruist appears to put other individual’s interests before their own. The general expectation is that the evolution of altruistic traits is not compatible with selfish gene theory. How could such a mechanism reinforce a behavior jeopardizing one's own interests at the expense of another's? Examples include self-sacrificing Behavior: e.g. vampire bats, guard bees, Cooperative breeding, e.g. African Kingfishers, Acorn Woodpeckers, Florida Scrub Jay;
- Social behavior relates to interactions with other members of the population. Group living comes with a diverse range of advantages and disadvantages.
- Society describes a group of individuals of the same species, organized in a cooperative manner, and extending beyond sexual contexts and parental care.
- Eusociality is an extreme form of altruism where sterile workers labor on behalf of reproductive individuals, cooperate in the care of young. There must be an overlap of at least two generations of individuals which share in colony labor.
Units of SelectionEdit
Discussion about the units of selection centers on an understanding of what the life of each individual is ultimately devoted to. This is nowhere more pertinent than in evolutionary explanations for altruistic acts or for the emergence of highly social societies. How could altruistic behavior ever emerge as a superior strategy if it actually diminishes the reproductive fitness of the individual showing it?
- Group Selection: In this view the unit of selection resides at the level of a group of individuals, where groups that contain a greater degree of cooperation would be expected to outcompete those groups that show less of it. Altruistic traits favor reproductive success of a group at the expense of that of an individual. Unfortunately, all members of a group with a high level of cooperation will derive the benefits, even those individuals who may be less cooperative than others. For several decades critiques have cast doubt on group selection as a major mechanism in evolution. "For the good of the group/species ..." explanations have not fared well in theoretical or empirical studies as over time selfish individuals in cooperative groups will outcompete the altruists.
- Individual Selection: In this view individuals are simply looking out for their own selfish interests
- Gene Selection: Is altruistic behavior focused on the preservation of selfish genes
Simple Egoistic SolutionsEdit
In some instances, benefits may accrue to an individual committing an altruistic act. If these benefits exceed its cost, it is in the egoistic interest of the individual to perform such an altruistic act.
Cooperation may be in each individual's egoistic interest if it increases its own individual fitness. Wolves, for instance, hunt in packs and then share their prey. Thereby each wolf benefits from pack hunting as the group can bring down prey that would be too large for a single individual. Although the behaviour may seem altruistic, individuals benefit directly in tasks that require many eyes. Fish tend to group in schools as it becomes significantly harder for a predator to pick out and hunt one specific individual from within their midst.
In 1971, Hamilton proposed the Selfish Herd model, which postulated a centripetal instinct that directs animals to place themselves towards the centre of a group. This behavior is based on a presumed increase in predation towards the outer edges of the group.
Young may remain with their parents and help them or group members raise more offspring, rather than breeding themselves (e.g., ostriches, some primates). Helpers may gain useful experience in raising their own offspring or have an increased chance to inherit a valuable breeding territory.
Reciprocal altruism exists in situations where individuals exhibit altruistic acts towards each other. For each individual the benefits accrued must exceed the costs it incurs.
Complex Egoistic SolutionsEdit
for Individuals: The Prisoner's Dilemma: e.g. Pukekos (Porphyrio porphyrio)
An individual behaves in such a way as to enhance the reproduction of another individual, at a cost to its own fitness. (e.g., Sterile workers in social insects who give up all reproduction for the benefit of their mother queen. Mutual or delayed benefits can’t account for this one: sterile workers never get to produce any daughters.)
An individual fitness solution to the paradox goes as follows: genes are favored that produce a disproportionate propagation of ones genes to subsequent generations even if it is at the expense of the individual. This may occur directly through either reproducing personally or indirectly by encouraging the reproduction of close relatives who share many of ones genes. Under those circumstances altruistic behaviors should primarily be directed towards close relatives who share many of the genes as compared to non-relatives who share fewer of them. Inclusive fitness refers to the sum of an individual's Direct Fitness (probability of reproductive success of one's own offspring) and its Indirect Fitness (probability of reproductive success of non-descendant relatives). Altruistic acts are frequently directed towards relatives. <Kin Selection>: selection for traits that lower an individual's personal fitness, but raise a relative's fitness. Recipient (related) kin share genes with the altruistic individual and are thus genetic extensions of them. Kin selection and inclusive fitness can explain sociality through increased survivorship of relatives, increased inclusive fitness, altruism, and delayed maturation or breeding.
Inclusive Fitness: refers to the sum of an individual's Direct Fitness (probability of reproductive success of one's own offspring) and its Indirect Fitness(probability of reproductive success of non-descendant relatives). Altruistic acts are frequently directed towards relatives. Kin Selection: selection for traits that lower an individual's personal fitness, but raise a relative's fitness. Recipient (related) kin share genes with the altruistic individual and are thus genetic extensions of them. Kin selection and inclusive fitness can explain sociality through increased survivorship of relatives, increased inclusive fitness, altruism, and delayed maturation or breeding. Kin selection favors behavior that sufficiently enhances the fitness of related individuals (i.e., carrying similar genes) leading to an increased representation of genes being passed on to the next generation.
Hamilton's Rule benefit to recipient / cost to altruist > 1 / coefficient of relatedness
The complex needs for group-living may have driven members towards a surprising degree of intelligence. Individuals of many species are able to keep track of each other's social status, correctly attribute each others mental states, and successfully engage in each other's deception.
- Wynne-Edwards, V.C. (1962). Animal Dispersion in Relation to Social Behaviour. Edinburgh: Oliver & Boyd.
- Wynne-Edwards, V. C. (1986) Evolution Through Group Selection, Blackwell. ISBN 0-632-01541-1
- Williams, G.C. (1972) Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Princeton University Press. ISBN 0-691-02357-3
- Maynard Smith, J. (1964). "Group selection and kin selection". Nature 201 (4924): 1145–1147. doi:10.1038/2011145a0.