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December 22, 2004

Green Beard Ethnic Nepotism? [Yes, Another Post On This]

Sailer and Salter's advocacy of kin selected ethnic nepotism using similarity data faces a major theoretical hurdle.

Evolution by natural selection concerns the change of the frequency of a specific allele at a given locus. In this sense, an allele competes with other alleles at this locus. It does not matter whether the effects of an allele increase the frequency of some alleles at other loci, a gene simply has to augment its own frequency to be evolutionary successful. For this reason, an allele that influences an organism in a manner that this individual behaves altruistically towards other individuals which are genetically similar to it with respect to other loci is neither selected for nor against. But genetic similarity theory focuses on overall genetic similarity, which basically includes all these irrelevant genes or loci. Instead, the question should be whether a gene is able to detect (based on phenotypic effects) whether another organism also has this allele at the same locus, then preferential behavior towards this organism is actually a better strategy than towards other organisms. But this scenario is simply the green beard effect, which as above said is usually excluded as a real possibility. This criticism has already been put forward by other authors (e.g., Mealey, 1985)...Standard kin selection theory, however, is able to give a possibility of the evolution of altruism. When a gene causes altruism towards a relative, this relative has—with a determined probability—the same gene identical by descent, and a fortiori identical in state. This is a clear way in which an allele can benefit the same allele in another organism (at least with a certain probability). (Brigandt in-press, pg. 10)

Dr. Harpending agrees with this criticism, but unlike Brigandt, apparently sees green beard effects as a possiblity. I want to take a look at this.

In some ways, green beard effects can better account for the peculiarities of ethnic conflict. Brigandt writes, with respect to van den Berghe's more traditionally Hamiltonian approach [1], that we would expect to see gradients of nepotism and ethnic conflict depending on how large the kinship coefficient is in any particular case. For example, we would expect Frenchmen to behave more altruistically toward each other than toward Englishmen, but more altruistically toward Englishmen than toward Poles. Wilson & Daly (via Jason) take this to its logical conclusion by suggesting "selection would have also favored altruism towards monkeys over dogs and mosquitoes over marigolds." However, "ethnic phenomena as ethnocentrism often have not only rather clear, but also distinctive boundaries. Either you are accepted as a fellow ethnic, or you are not. This does not conform to homeopathic altruism."

But this wouldn't be so strange if they are green beard effects. Ingroups and outgroups, according to the green beard hypothesis, are clearly delineated; either you are a member of the group (have the green beard gene or genes) or you are not (lack the green beard gene). Still, I see more problems and inconsistencies than solutions. For example:

1) If ethnic nepotism is a green beard effect, similarity data is still irrelevant. What matters is the presence or absence of the green beard gene (or tightly linked genes) but not similarity of other alleles across all loci.

2) Though possible, green beard effects are very rare. Dr. Harpending mentioned the fire ant gp9 locus, but an additional search of the literature yeilded only two more examples, within the slime mold Dictyostelium and possibly the poison-antidote system of bacteriocin producing bacteria.

3) The hypothesis would require the parallel acquisition of different versions of these genes in all ethnic groups that exhibit nepotism. Coupled with the second point, it seems highly unlikely that an ultra-rare phenomenon would repeatedly evolve in such a short amount of time, within such a phylogenetically exclusive group.

Minimally, this needs to be subjected to experiments before we jump on the bandwagon.

Ethnic Genetic Interests: Part 2
Ethnic Genetic Interests
Interracial Marriage: Salter's fallacy
Limits to Hamiltons Rule
On Genetic Interests
Dissin' Dawkins

[1] I say Hamiltonian approach because van den Berghe, unlike Rushton and (apparently) Salter, relies on the relatedness of individuals by descent and not their allelic similarity across all loci.

Posted by God Fearing Atheist at 03:57 PM