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Why Is Altruistic Behaviour Problematic For The Theory Of Natural Selection?

Nice guys finish first, a chapter title in R. Dawkins' revolutionary popular science book the Selfish Gene. Although true altruism can not exist according to the classical theory of natural selection if such an evolutionary protagonist as RD has time for it, then there must be a good reason. In fact, we see much behaviour in nature that appears altruistic: alarm calling, guarding, defence and foraging by non-reproductives and grooming are just a few examples. Since work first began on altruistic behaviours, various mechanisms have emerged that have been able to squeeze them into the conventional model of natural selection. However, by no means can all altruistic behaviour now be explained by these methods.

First, altruism must be defined so we can see how it defies the conventional theory of natural selection. Perhaps more importantly we must then ask why, when inexplicable using Darwin's original model for selection, we still frequently observe altruism in nature. Three answers to this question have been put forward: kin selection, group selection and reciprocation. These will be examined in order.  

When an actor's behaviour increases the fitness of the behaviour's receiver at the expense of the actor, then the behaviour is said to be altruistic. This definition is simplistic but provides a good starting point; throughout the discussion it will be sharpened. In contrast to so-called selfish behaviour increases the actor's fitness while reducing the fitness of the receiver. If both the actor and the receiver gain in fitness following a behaviour, then the behaviour is cooperative. We must keep in mind that these costs and benefits are measures of reproductive success, the number of offspring surviving to reproductive age and thus the number of genes passed to the next generation.  

It is worth mentioning that much altruistic behaviour may directly benefit those performing the behaviour in a way that may not be immediately obvious to the observer. Guard...