What is it about?
Sexual selection was Darwin’s other great idea. Modern biologists see it working as a result of a correlation between (1) genes coding for attraction towards a particular trait and (2) genes coding for the trait itself. In this study we measured: 1. preference towards mates who display altruistic traits and; 2. the altruistic traits themselves by using two psychometric scales (i.e. questionnaires). To test for the influence of genes on responses to these scales we employed a twin study. This involved comparing the responses of identical twins (who share the same genes) with those of non-identical twins (who have a 50% chance of sharing any given gene). Because we were able to compare individuals with known levels of relatedness and environmental influences we could estimate the effects of genes and environment on variation in responses. We could therefore test whether human altruistic behaviour might have evolved as a result of sexual selection.
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Why is it important?
Our results demonstrated that genes influenced variation in responses to both scales (i.e. attraction towards altruism in a mate and altruistic behaviour itself). We also found a correlation between mate preference and preferred trait and that 67% of this correlation was influenced by genes. These results are consistent with human altruistic behaviour having evolved as a result of sexual selection.
Perspectives
The prevailing view in science continues to be that altruistic behaviour is explained by reciprocity theory (i.e. direct, indirect and generalized reciprocity) whereby individuals reciprocate altruistic acts over time. However, there is a scarcity of clear-cut evidence to support this theory despite more than 40 years of searching. Indeed, one study found evidence that appears to falsify the theory. In contrast, there is mounting evidence for a link between human altruism and sexual selection of which this study is one example.
Tim Phillips
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This page is a summary of: A link between altruism and sexual selection: Genetic influence on altruistic behaviour and mate preference towards it, British Journal of Psychology, November 2010, Wiley,
DOI: 10.1348/000712610x493494.
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