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Apparent Altruism and Limitations of the Evolutionary Approach
Evolution should cause selfishness to be adaptive because it will improve an individual's survival and potential reproductive success.
But what about altruistic behaviours, in which other animals benefit as a cost to the donor?
Before looking at the biological explanations for this, it is important to banish a demon. This one is called group selection (Wynne-Edwards, 1962). Animals do not gain a selective advantage by behaving in such a way that the group or species benefits. A group comprising these organisms would be open to exploitation by selfish animals.
So 'cheats' in the population would be more successful and spread, thereby out-competing the altruistic animals or 'suckers'!
There are two situations, however, when it could be beneficial to the inclusive fitness of an animal to behave in an apparently altrustic manner. In these situations, natural selection would favour such behaviours:
Kin selection (Hamilton, 1964): If those animals receiving the benefits are close relatives they will share a large proportion of their genes with the donor (a high coefficient of relationship).
If the 'altruistic' act allows the recipients to leave more offspring, the donor will have at least some of his/her genes passed on. (This means that natural selction does not operate at the group level, nor even the individual level, but at the genetic level).
The apparent altruism seen in social insects, such as ants and bees, can be explained by kin selection because the workers are very closely related.
Reciprocal altruism (Trivers, 1971): Sometimes unrelated animals may show signs of altruism towards each other. This behaviour is adaptive as long as the favour is returned or reciprocated at a later date. The benefit to the recipient must be greater than the cost to the donor for the behaviour to evolve.
Here's a question for you:
What stops a vampire bat from exploiting a reciprocal arrangement to get extra blood?
The "tit-for-tat" strategy in vampire bats is a commonly occurring example of an evolutionarily stable strategy (or ESS, for short!).
This means that if most of the population adopt the behaviour pattern, it cannot be beaten by any other strategy.
Predictions about the way in which an animal should behave to maximise benefits and minimise costs can be made using game theory (an economic theory stolen by animal behaviourists).
One type of game is the Prisoner's Dilemma, which models the behaviour of two individuals who could co-operate with each other (resulting in a mutual advantage) or try to stitch the other up (a big pay-off for the successful 'cheat')!
So, we've reviewed the theory and the evidence, but what about the limitations? Most of the criticisms focus on environmental influences outweighing the genetic factors:
Nature vs. nurture: Behaviours arise trough an interaction of genetic and environmental influences. This suggests that the evolutionary approach can only tell part of the story.
Cultural evolution: Behaviours may be transmitted through imitation from one individual to another, good behaviours spreading more rapidly than less beneficial ones. This becomes more common higher up the phylogenetic scale, which makes people reluctant to accept the evolutionary approach as an explanation of human behaviours.
Some criticisms focus on the methods of the evolutionary approach:
Pick 'n' choose: It has been suggested that the examples to demonstrate the evolution of behaviours are carefully selected and that many behaviours are ignored (Hayes, 1994).
Remember that these are criticisms of the evolutionary approach as explanations of animal behaviour. The theory of evolution is not disputed in scientific circles.