Evaluate Hamilton's rule using specific behavioural examples

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Evaluate Hamilton’s rule using specific behavioural examples

In evolutionary terms costs and benefits are continuously weighed up among primates to ensure successful reproduction and survival among their species. Although it seems that various species are in competition within and between each other to ensure the survival of the fittest, this has not necessarily been demonstrated to be the case. Some kind of altruism also exists among primates in order to maintain survival. For example prairie dogs give alarm calls to warn other individuals about potential predators, although this greatly increases the risk of them getting spotted themselves.  

Hamilton (1964) proposed a theory that facilitated with answering some of the questions within the apparent paradox of altruistic behaviour. He suggested that fitness is measured in terms of the number of genes passed on as oppose to the number of offspring that is produced. He suggested that individuals can increase their fitness in two ways. Firstly they can directly pass genes on to their own offspring. Secondly, they can aid the reproduction of others that are likely to carry the same genes. Consequently, an organism’s fitness is made up of two components, direct and indirect fitness which combine to give a measure known as ‘inclusive fitness’.

Hamilton’s solution to the problem of altruism was that a gene for altruism could evolve under Darwinian selection if the altruist’s behaviour allowed a genetic relative that shared the same gene to reproduce more than it would otherwise have done. However, one implication of this is that one would assume that an individual should always prefer to aid kin that are closest to it rather than distant to it, as the chances of sharing the same gene is likely to be higher with close kin.

This theory is summarised into a formula generated by Hamilton known as Hamilton’s Rule. This rule suggests that a gene for altruism will evolve whenever

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r B > C. In this formula B is the benefit to the recipient of the altruistic act, C is the cost to the actor and r is the coefficient of relatedness between the actor and the beneficiary. In other words r measures the probability that any two individuals share the same gene because they inherited it from the same common ancestor. Calculating r within our species is relatively simple. For example we inherit half our genes from our mother and half our genes from our father. Therefore the r value between an individual and their mother is 0.5, and ...

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