Genetics issues in ancient India

[Steve Farmer]

I wrote:

> >It is important to note that mtDNA studies like this may not be
> >as relevant to invasion/migration issues as studies of y-chromosome
> >polymorphisms.

Vidyasankar Sundaresan responded:

> mtDNA studies may not be relevant only to those who assume that
> the incoming Aryans were all male, who took native female partners.
> This assumption reveals more about the inadequacies of the theory
> than about the inadequacies of mtDNA studies themselves. If the
> incoming Aryans were a mixed population of males and females (as
> I would expect them to have been), mtDNA studies will still have
> important contributions to make.

You've distorted my message, whose intent was to point to the
abstracts of fifteen genetics papers potentially relevant (either
way) to the Aryan question. I took no stand either way in the
post on the Aryan migration issue itself. Those abstracts are
listed at http://www.safarmer.com/genetics.

But NB: What I said was that mtDNA studies "may not be as
relevant" as studies of y-chromosome polymorphisms to the Aryan
question — not that they "may not be relevant" at all. This
difference isn't trivial.

Moreover, your claim that methodological problems in the use of
mtDNA studies only arise for "those who assume that the incoming
Aryans were all male, who took native female partners" is by no
means correct. It is common for dominant/elite males in migratory
cultures, whether or not they are accompanied by females, to mate
with native females. This skews mtDNA data in ways that do not
occur when you use studies of y-chromosome polymorphisms, which
exclusively pertain to paternal lines. Hence the enormous
interest at present in population genetics in studies of
y-chromosome polymorphisms.

You write:

> Both your stand and my response above rely on the current paradigm
> that mtDNA is derived solely from the female line. This is, in turn,
> based on the observation that in most species, sperm cells do not
> contain mitochondria, or that if they do, mitochondrial material
> is digested after fertilization of the ovum. This picture is now
> becoming more complex. In some mollusc species, it is already well
> accepted that mtDNA show bi-parental inheritance. Human sperm does
> have mitochondria, and I am keeping an eye open for the possibility
> that mtDNA lineages may not be solely maternal.

What you say is correct, but it further undercuts your own
position. The data published by Strauss in _Science_ 286 (24 Dec.
1999) suggests that paternal and maternal mtDNA sometimes do
undergo sexual recombination. How and when this occurs is not
currently known. What *is* certain is that if this is a normal
situation, the value of mtDNA studies in investigating
migrational patterns is attenuated even further. The so-called
Eve thesis, for example, which is already under attack for
different reasons, would collapse completely. This points again
to the increasing importance to migrational studies of data on
y-chromosome polymorphisms -- as suggested in my post.

Again, a friend from Cavalli-Sforza's group, a specialist both in
migrational and y-chromosome and mtDNA issues, will report on the
relevance of these questions specifically to the Aryan problem at
a Harvard conference next May.

In sum: There are good reasons why population geneticists
currently place more hope in studies of y-chromosome
polymorphisms, and not in mtDNA research, in attempting to
unravel migrational issues.

Steve Farmer