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Health

Altruism & E.O. Wilson vs. Richard Dawkins

Gene ExpressionBy Razib KhanJanuary 11, 2008 6:26 PM

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There have been a spate of articles about E. O. Wilson'sdrive to put group selection back into mainstream conversation among evolutionary biologists over the past year.

Wilson has kept the torch alive for this particular paradigm since the 1970s, when it was prominently featured in his famous book Sociobiology.

At the same time as Wilson was making waves in the United States Richard Dawkins debuted with The Selfish Gene, a book where he explored the new ideas of theoretical biologists W. D. Hamilton and J. M. Smith. Hamilton's model of kin selection, which he debuted in the mid-1960s, ushered in a revolution in the social theory of evolution and heralded a long twilight for group selectionist theories (the philosophical decapitation was implemented by George Williams). Through this period Wilson refused to be swept away by the swelling tide, and in his book Evolution for Everyone David Sloan Wilson recounted how as a young scientist he was encouraged to explore this topic by the older Wilson. So what happened to prompt E. O. Wilson to become more vocal? I don't know much about ethology, but when I did poke into the literature a few years ago I stumbled on to some papers which expressed skepticism about the explanatory power of kin selection to explain eusociality among haplodiploid insects. Specifically, consider Hamilton's Rule: rB - C > 0 That is, the coeffecient of relatedness to an individual times the benefit to that individual minus the cost to yourself must be greater then one for an act to be genetically rational. In other words, if you increase the fitness of your full sibling my more than twice the reduction of fitness to yourself then the act will be genetically favored. For a cousin, you have to multiply the increase by four, because a cousin is only 1/4 as related (coefficient of relatedness 1/8 as opposed to 1/2). Among hymenoptera (e.g., ants, bees, wasps, etc.) the haplodiploid inheritance system implies that sisters should be more closely related to each other than to their offspring. This means that increasing the fitness of a sibling (i.e., a sister queen) might be more genetically optimal than producing your own offspring! More precisely, drones are haploid, while females are diploid. Full sisters share at least 50% of their genes via their father. From their mother they should share another 25% (remember, the mother is diploid, so she can contribute varied copies). So the expectation is that full siblings will be related on the order of 75%! This makes Hamilton's Rule a lot easier to satisfy. A theoretical problem is that queens may be fertilized by the sperm of multiple drones, which might result in far lower than 75% relatedness. Additionally, not all haplodiploid insects are eusocial, and not all eusocial insects are haplodiploid. This means empirically we always knew that haplodiploidy is not necessary nor always sufficient to produce eusociality. My understanding though is that with DNA fingerprinting entomologists have attained a much finer grained understanding of the relatedness of individuals within hives or colonies, and it necessitates the generation of a more complex picture. This means that though the press loves a fight, this is ultimately a debate about semantics and emphases, a difference of degree and not kind.Note: Definitions matter here. Richard Dawkins believes it is important to make a distinction between replicators and vehicles. A lot of the popular press pieces are sloppy in that they juxtapose gene level selection and group selection. This means that one is really contrasting meiotic drive with interdemic competition. I really don't think that this is the intent. All selection affects evolutionary change via differential replication of genes, the real debate is about the unit of selection. Also, I have a close friend who is in Wilson's department at Harvard, and from personal communication I can confirm that he has convinced very few of his colleagues at the same institution. Related:Zooillogix has some comment on this issue. Cooperation and multilevel selection.

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