Re: Dating with DNA? Problems and Current Approaches

On Wed, 13 Sep 2006 14:36:31 GMT, prd <X_header@xxxxxxxxxxx> wrote:

In sci.archaeology message
news:2a0fg2d4jck074di321uk0jrncoh376498@xxxxxxx by G Horvat
<g-horvat@xxxxxxx> . . . :
[...]
By "type", do you mean haplogroup (H, V, J, T, U, K, etc.)?

By type I mean the exact genomic mtDNA type or derivatives.

Micheal posed a hypothetical question, actually 2.
I introduced the genomics to the question.

1. If there was uncovered today a find such as "Oetzi", is
there a reasonable chance that one could date the find
based on its genomic mtDNA sequence. I doubt this because
of the distance between mutations and variation in mutation
rates.

2. If there was a find from 20,000 years ago, is there a
reasonable chance that one could date the find based
on its genomic mtDNA sequence. IOW is there a reasonably
good chance of finding alot of 'surface' mtDNAs that are
reasonably descendant from this find or the best one can
hope for are side branches and distal branch points.
This prospect seems do-able but one would need a really
good database.

So I asked the question, what is the current state of
the database.

In the New World, we have sequences which must have diverged from
Asian ones 10,000 - 30,000 years ago. I am, of course, familiar with
what is available concerning them and while I would like a much better
Native American database, it is my opinion that this will not result
in more secure dates. The problem, again in my opinion, is the
necessity to incorporate estimates into any formula used.

The more secure information derived from complete mtDNA sequence
comparisons concern relationships and that's what I concentrate on.

The closest sequences to the Native American ones now belong to many
branches.

[...]
RFLP misses mutations and really genomics are needed to be certain
of all positions, those little minute mutations are important
for dating since they reveal the time since the first instance
of a mtDNA preceding the branch points.

RFLP was used for classification purposes rather than dating.

Gisele
.

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