Third cousin crush:
I have heard two opinions on how long it takes for an idea in science to take hold with the public. The first opinion was that papers appear in the literature for about two years, then the newspapers take notice for about two years and finally the public interest groups begin to appear. The other opinion was that it takes thirty years for a new idea to become accepted. I suppose the idea that one needs to balance kinship – not too much and not to little – for optimal fertility falls into the thirty year sort. The question that remains is when the clock starts. I would say the Sibly article I cite regularly would be the latest one might say it all started. I had been working on it for some time, but since I do not leave tracks, unfortunately, history is going to look back to Sibly and possibly no earlier.
However the clock may have started in 1978, in which case all bets would be off, wouldn’t they?
I have in hand an article, a brief letter (Biological Basis of the Third Cousin Crush Johan A. Lundström et al. SCIENCE vol. 320 no. 5880 May 2008 page 1160) that cites the Helgason article I also frequently refer to. The Lundström article takes an interest in the mechanism for the relationship between kinship and fertility. Their suggestion is that the process is mediated by the major histocompatibility complex.
You know you can’t graft the tissues of one person onto another person without a great deal of effort to control the immune system unless the two people are identical twins. The incompatibility with foreign tissue is mediated by something on the cell surface, called the major histocompatibiltiy complex. One element of the complex, and the one that gives it its specificity, is protein, good old fashioned protein coded for by a good old fashioned gene. If they match, the new tissue is – other conditions being acceptable – accepted.
My own opinion is that the phenomenon is more likely to be due to epigenetic effects than to genes. It evolves too fast to be genes. And anyway, most of the Jews in America seem to be related – so far as their genes go – as close as about fifth cousin. Their fertility should be quite adequate. That does not appear to be the case.
On the other hand, if the major histocompatibility complex is being used as a clue for the proper degree of kinship between members of a human or animal couple, I should not be surprised at all.
Well it is good to know that somebody else is thinking about the need for a balance between novelty and familiarity in mating choice.
The article cites another article (P. Bateson, NATURE vol. 295 page 236 (1978)) that suggests this was going on and another article one year later that demonstrated such behavior in birds.
More power to them.
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