Does <0.5 Fst invalidate taxa?

[Over 9000]

The term subspecies is certainly not used ubiquitously to describe any level of genetic partitioning below the species level, and I'm repeating myself, but it's generally used using criteria specific to each organismal group as a matter of convenience - see previous "irrelevant" Trypanosoma example.

 

Repeating myself again, one can certainly make some sort of case that human populations represent "subspecies" - however I would suspect that broad acceptance of such a classification would be impeded by the fact that the vast majority of genetic variation is within groups, and identification of hybrids (e.g. F1, F2, backcrosses) would be challenging due to long term genetic transfer between groups, rendering such a classification system of limited practical utility.

 

Indeed we are repeating ourselves again! But it's always fun to really try to drill the actual truth into the public conciousness, in the face of determined obfuscation by so-called experts.

 

Is "more variation within groups" a problem for other subspecies? Is it in fact normal? Is this just an ad hoc race denial fallacy only applied to humans and originating from the avowed Marxist Richard Lewontin and parrotted endlessly by social science departments?

 

Let's take a look.

 

 

 

It is genuinely true that, if you measure the total variation in the human species and then partition it into a between-race component and a within-race component, the between-race component is a very small fraction of the total. Most of the variation among humans can be found within races as well as between them. Only a small admixture of extra variation distinguishes races from each other. That is all correct. What is not correct is the inferene that race is therefore a meaningless concept. This point has been clearly made by the distinguished Cambridge geneticist A.W.F. Edwards in a recent paper “Human genetic diversity: Lewontin’s fallacy.” R.C. Lewontin is an equally distinguished Cambridge (Mass.) geneticist, known for the strength of his political convictions and his weakness for dragging them into science at every possibile opportunity. Lewontin’s view of race has become near-universal orthodoxy in scientific circles. He wrote, in a famous paper of 1972:

 

It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals

 

This is, of course, exactly the point I accepted above, not surprisingly since what I wrote was largely based on Lewontin. But see how Lewontin goes on:

 

Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxnomic significance either, no justification can be offered for its continuance.

 

We can all happily agree that human racial classification is of no social value and is positively destructive of social and human relations. That is one reason why I object to ticking boxes on forms and why I object to positive discrimination in job selection. But that doesn’t mean that race is of “virtually no genetic or taxonomic significance.” This is Edwards’s point, and he reasons as follows. However small the racial partition of total variation may be, if such racial characteristics as there are highly correlated with other racial characteristics, they are by definition informative, and therefore of taxonomic significance.

Emphasis added.

 

Wright's (inventor of F statistics) values:

 

<0.05 = little genetic diff.

0.05-0.15 = moderate genetic diff.

0.15-0.25 = great genetic diff.

>0.25 = very great genetic diff.

Edited November 10, 2016 by Over 9000