#kinselection

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PART I: Hamilton's Inclusive Fitness Theory or Hamilton's Rule | Altrui...

[thesocialgene-blog]

Featureless Paddock

I will now return to the notional experiment that launched the hypothesis of the social gene: the featureless paddock that allowed the interpretation that a proximity reward caused some varieties of sheep to congregate together. When I discussed it originally, I did not explain that the purpose of those experiments had been to test whether the two genders formed single-sex groups. Perez-Barberia and co-workers showed conclusively that feral Soay sheep formed separate groups based on gender within a symmetric paddock in conditions that precluded estrus. Segregation did not occur within any single-sex group, including groups composed of mixed small and large animals that might be expected to exhibit size-dependent activity differences. On the other hand, strong and nearly equal segregation occurred in a random mixed-sex group and in a similar group that contained only animals that were of approximately the same size in both genders; i.e. relatively large females and small males. Foraging and resting synchrony of the mixed-sex groups was also significantly lower than those of single-sex. Since there was no size dimorphism in one of these categories, they concluded that it was not responsible for segregation. On the other hand, the observations were consistent with their alternative hypothesis that social affinity accounted for the formation of the single-sex flocks. This simple observation fulfills the definition of a reward that is conferred on each gender separately and provides the underlying basis of sexual segregation; it may be described as a “homosocial proximity reward”.   A definitive experiment or observation need not be complicated; indeed, some of the most dramatic events in scientific history have been no more than simple observations. When Galileo watched objects of different size and density falling from the leaning tower of Pisa at the same rate, he reshaped the principal claims of ancient Greek philosophers. When Eddington, at Einstein’s instigation, observed that stars modified their apparent position when their light passed close to the sun during an eclipse, he confirmed both the special and general theories of relativity. The featureless paddock experiment is not one of those categories, but, in its small way, it has opened the door to a reevaluation of animal sociality. It showed that animals associate spontaneously without an external stimulus, that they separate by gender and that this is not caused by differences in size.   Perez-Barberia- “One possible explanation of the results of our study could be the social affinity hypothesis (Bon et al. 2005, Conradt 2005, Michelena et al. 2005). But, why should animals show an affinity for animals of the same sex?” Bon- “Mechanisms proposed to explain social segregation in children, and data collected on behavioural development and social interactions in other mammal species inspired the social affinity hypothesis”   One can glean from these discussions that a few experimental investigators have moved beyond the millstone imposed by evolutionists, in order to explain their field observations. In particular, Bon et al. have broken the taboo of comparing animals with humans. Their conclusions do not directly address kin selection, but they do discuss social affinity without reference to it.   Read the full article

[thesocialgene-blog]

Recognition

According to kin selection theory, herds can only form when animals are related to each other and when affiliation between individuals is proportional to the closeness of genetic relatedness. It would be expected that this should require each animal to be able to recognize its closest kin. This raises a difficulty with many ungulates who separate into distinct bachelor and nursery herds. The males only meet up with the females at mating time and, therefore, are absent at the time of the birth of the next generation. It is doubtful that they even understand that mating gives rise to new infants. Moreover, they only meet the new crop of juveniles of either gender briefly at the next mating season when their attention is directed to the opportunities of mating presented by the ewes. Therefore, mature males have no reason to speculate on the identity of their progeny or any other potential juvenile relatives and it may be considered unlikely that they experience a sudden recognition of kinship when the newly mature males join the bachelor herds. The picture is more favorable for the ewes to recognize and respond to immediate relatives, since at least they know their own progeny and may be familiar with lateral relatives who remain in their established territory throughout their lives. A potential solution to the problem of recognition has been offered by the supposition that the animals do not need to know their relatives as long as the aggregate is in practice composed of closely related individuals. The argument is that a subject might be attracted to all of the other members of the herd. This may be true, but it dilutes the impact of the hypothesis by making kinship an approximation rather than a necessity. Nevertheless, there are costs to this particular version of kin affiliation. Dawkins, in The Selfish Gene, employed field data provided by Brian Bertram to present the scenario of a pride of lions composed of seven resident lionesses and two lions who are itinerant. With further reasonable assumptions, the average relatedness of the males was computed to be 0.22 and that of the females to be 0.15. The measure of social affinity between two females of unknown relatedness is slightly less than a third of what might be achieved with a full sister, had she been able to detect her kinship. The figure of relatedness for the males is less than half that of a full brother. If a choice must be made to engage in social behavior with another animal, there are clear advantages to knowing its degree of relatedness.   The arguments discussed here are yet one more example of proponents justifying kin selection by introducing an additional interpretation, that the degree of relatedness is that of the herd rather than the individual. In effect, they are arguing that measurements of relatedness are irrelevant to the theory (which explicitly places kinship at its center). We will see later that more sophisticated measurements do not support even this speculation. I have not discussed yet another apologia of the theory, that animals may detect their kin by smell. Read the full article

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SOCIAL GENE vs KIN SELECTION IN DESCRIBING ANIMAL SOCIALITY. II: THE EVIDENCE

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

[thesocialgene-blog]

SOCIAL GENE vs KIN SELECTION IN DESCRIBING ANIMAL SOCIALITY: I: THE THEORY

(The Social Gene chs 1 & 3) In a world defined by Darwin as one of relentless competition for success in producing offspring, evolutionists were confronted by the existence of altruistic gestures between individuals. They resolved this paradox in the theory of “kin selection” by granting a waiver for close relatives on the grounds that their genes were almost identical to each other, and so those favorable genes of the subject could be propagated almost as effectively by these relatives. The doctrine of kin selection was described by William Hamilton as: “If natural selection followed the classical models exclusively, species would not show any behaviour more positively social than the coming together of the sexes and parental care. ”1 Richard Dawkins offered a similar sentiment: “... a predominant quality to be expected in a successful gene is ruthless selfishness.” 2 In this interpretation of evolution these authors have concluded that the sole purpose of sociality is contained in its benefit to close relatives. This appears to be the fulfillment of the dogma of “natural selection” proposed by Darwin, although he did not express this view. In deconstructing this hypothesis the first decision is whether it is justified in its own right without further explanation as is implied by the quotations. I will argue that there are no grounds a priori to conclude that either expression is established in fact or in theory. Delving Deeper into the Faulty Hypothesis of Kin Selection For the sake of argument, let us take the opposite position that animals may benefit from being unselfish. The criteria for determining which is most likely to be true will be whether the needs of the individual and the species are furthered. A first impression would suggest that natural selection favors the first interpretation by promoting the success of the individual in competition with other members of the species. In many species - those that are not social – conflicts may occur between individuals when they meet each other. A case in point is the Arctic Fox that pounces on small prey in their burrows and would not appreciate competition. Sociality offers no benefit to the individual or species in this example. In contrast, cooperation is intrinsic to African Wild Dogs who depend for their survival on their ability to take down preys that are much larger than them in the open savannah. They achieve this by forming packs that are optimal in size for their task and without redundancy. Ruthless selfishness plays no role in the act of hunting in their society. They precede their hunts by performing a chorus of joyful yapping and all members join in the feast of a successful kill. The hypothesis, then, depends on whether kinship is the basis of the pack. It certainly seems as though the dogs receive a strong motive to cooperate and that this applies independently of family connections. I have presented the evidence that kinship is not a prerequisite for sociality in The Social Gene and address the failures of kin selection further in the second article “II: The Evidence”.   1. Hamilton W. D. J. . (1964) The Genetical Evolution of Social Behavior. I. Theoret. Biol 7, 1-16 2. Dawkins, R. (2006). The Selfish Gene (No. 199). Oxford university press. Read the full article