Lost Haplotypes

A bit more on admixture.

Following up on this.

One must remember that the farther back an admixture event is, the more difficult it is to detect, at least with the 23andMe methodology.  Over time, haplotypes are broken up by recombination and, after a while, the intrusive alleles become part of a group’s native genome and are possibly no longer recognized as admixture.  This is particularly true if the admixture is small.

This, if group X is a mixture of A, B, and C in historic times, this is fairly easily detected, even if components B and C are relatively minor.  Going back much farther in time, it is not so easily detected, and the genetic combination of A, B, and C is just considered as “pure X.”  The ancient combination blend is no longer easily discernible – by methods looking at haplotypes and using extant populations as the parentals (ancient DNA is another matter, see below).

Some would say using NRY and mtDNA would help in this regards but those are single locus markers very sensitive to population replacement events.  If the degree of admixture was relatively small, and ancient, there may well be no trace using those uniparentally inherited markers.

Then again, access to ancient autosomal DNA, utilizing appropriate methods, can (and does) detect ancient admixture, which is why the European genepool can be viewed as a mix of ancient components, and that’s fine, but with respect to “racial admixture” as is commonly perceived the problem still exists. When people, particularly heavy-breathing Nutzis, talk about admixture, they typically refer to the various racial groups extant today; they do not refer to ancient tribal groups making up the bulk of the European genepool nor do they refer to Neanderthal gene variants that are a normal part of that genepool.  And it is precisely the type of admixture that Der Movement worries itself so much about that is characterized by the problem discussed here.

It is possible that the existence of such “occult” ancient admixture could explain unusual phenotypes observed at low frequencies in populations thought to be (relatively) “pure.”  Alleles from intrusive groups exist, “scattered” throughout the population, but not recognized as intrusive, but instead viewed as part of the normal gene frequency pattern in these populations.  Such alleles may happen to be more prevalent in certain families, and through random mating events (independent assortment, recombination) may become concentrated in particular individuals – resulting in an “atavistic” physical appearance reflecting low levels of (near) undetectable admixture in the population.

Of course, on an individual (or even family), even with more recent admixture, recombination can dissociate alleles coding for phenotypic traits from other alleles typically used to ascertain ancestry, particularly when the former are few in number (e.g., for isolated traits or sets of traits).  On a population level, this may be less of a problem for more recent admixture, as these things average out, but for more ancient admixture, the issue described above still may hold.

Possibilities such as this, and the inherent problems in ascertaining very old low levels of admixture fly night over the heads of Type I ethnic fetishists.  On the other hand, these problems may actually be desirable for some, as the outcomes reinforce pre-existing dogma.