Re: First Americans Arrived Recently, Settled Pacific Coast, DNA Study Says

In sci.archaeology message news:eqnil0$edv$1@xxxxxxxxx by "Uwe Müller"
<uwemueller@xxxxxxxxxx> . . . :


"Jack Linthicum" <jacklinthicum@xxxxxxxxxxxxx> schrieb im Newsbeitrag
news:1171209545.500210.272980@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

snip >


By measuring the rate of mutation, Kemp found that so-called molecular
evolution-the process by which genetic material changes over time-had
taken place two to four times faster than researchers believed mtDNA
could evolve.

That, Kemp said, suggests people entered the Americas within the last
15,000 years, because the DNA has evolved too fast for the arrival to
have occurred any earlier.

snip >

The first paragraph boils down to something like: all dates arrived at
via genetic dating could be divided by 2 or even 4. That would have
enormous consequences for the
population/repopulation-after-the-ice-age-scenarios in Europe.

The second paragraph seems to imply some doubts about the dating. If the
dating is correct, an age of 10300 for the sample, no method of dating
given, than the mutation rate should have to be roughly trebled. If the
mutation rate is trebled, the amount of genetic change apparent in
modern descendants would argue against an aearlier arrival than ca.
15000.

If the dating of the tooth was not correct, the mutation rate may remain
unchanged, or could be changed according to personal preferences. There
would be no argument against earlier arrivals.

So everything rests on one tooth, and how it was dated. Does anyone know
how it was done? A carbon 14 dating could be easily off because of the
influence of marine carbon, as they were said to exploit coastal
ressources. Was it dated by the date of the layer of extraction?

Their conclusions are not warranted, the 96% confidence interval for
the persistence of a founding haplotype is 0.04 = 1/2^N where N = number
of halflifes. 2^N = 25 N ~4.5 halflives. If the estimated rate of evolution
is 1 event per locus of 9 to 28 ky then the rejectable timings would be
40 ky + 10,000 years. Therefore the conclusion of the abstact is not
scientifically secure and a bad use of statistics. Even if they were using
genomic DNA which has 5 times the number of relevent mutations their
rejection criteria would be in excess of 15,000 years or more.
.