#geneticprofiling

Despite the long history of the theory of kin selection, it has never been confirmed through unambiguous observation or experiment. Neither of the two authors in the previous blog seems to have had much interest in testing their ideas. In order to understand kin selection theory, one must recall the effect of the degree of separation of pedigree of two related individuals on the degree of identity of their genes. The basic rule is that for each degree of separation it drops by a factor of 2. Parents, progeny, and siblings are all, on average, half-identical, while uncles, nieces, grandparents, and grandchildren are a quarter, and cousins an eighth identical. The general effect of this exponential decline should be to give preference to small compact herds. Kin selection is not a feasible explanation for massed herds of species such as reindeer, wildebeest or emperor penguin. Moreover, Kay Holekamp has reported that hyena colonies are also generally only loosely related. Coltman et al have used genetic profiling to show that female wild sheep herds are related only to the extent of second cousins, while the males are unrelated1—and so it goes on. The Limit of Kin Selection in Animal Sociality Kin selection is a possible explanation for small herds of deer, sheep, and bovines. But, they all present a problem for males who may not even recognize their offspring, since they are absent at the time of their birth; when the two genders meet at the mating season in the next year they are more interested in sex than in their progeny. In this and in many other cases, in which the hypothesis has been challenged, partisan commentators have responded by modifying the theory with untested explanations. Edward Wilson has expressed his frustration with this unscientific practice in “The Social Conquest of the Earth”. Some animals act generously to those in distress by assisting them even to their own detriment. A good example of this is the adoption by macaques, chimps, hyena, and humans of orphaned infants and nursing them for long periods. Genetic profiles have shown that many of them are not related to the surrogates, which is a direct breach of the rules of kin selection. Hyenas nurse the infant orphans for more than a year and eventually incorporate them into hyena society, while receiving no tangible benefit to themselves.2 Among the chimp surrogates are some males, who do not normally engage in rearing.3 These observations contravene the “ruthless selfishness” of Dawkins. Some male baboons, who move into a new colony, team up with nursing mothers to protect the offspring from rough treatment by other members of the community, even though they receive no reward for this.4 What is Group Selection? An alternative to kin selection, called ‘group selection’, has been championed by the Wilsons (David and Edward); as its name implies it argues that genes may be propagated that benefit the whole society rather than the individual.5 This may indeed be a more realistic description of animal societies. However, it suffers from the drawback that it does not really advance our understanding of sociality. Asocial species do not benefit from group selection, because they do not form groups. Social species do receive a benefit, since this is an evolutionary requirement for the propagation of a trait, but where is the mechanistic explanation of how group selection arises? The time has come to abandon evolutionary explanations which have proved so unsatisfactory, and to turn to physiological approaches for understanding animal interactions: The Social Gene (blog #3. Social Genes). 1Coltman, D. W., Pilkington, J. G., & Pemberton, J. M.. Molecular Ecology, 12, 733-742. (2003) 2East ML, Höner OP, Wachter B, Wilhelm K, Burke T, Hofer H. Behavioral Ecology. 20:478-83. (2009) 3Boesch, C., Bole, C., Eckhardt, N., & Boesch, H. PLoS One, 5, e8901. (2010). 4Nguyen, N., Van Horn, R. C., Alberts, S. C., & Altmann, J. Behavioral ecology and sociobiology, 63, 1331-1344. (2009) 5Wilson DS, Wilson EO. American Scientist.;96:380-9. (2008) Read the full article