Genetic Structure of a 2,500-Year-Old Human Population in China ...

> Original from: chingdude56
> Sent: Thursday, October 31, 2002 9:10 PM
> To: cybalist@yahoogroups.com
> Subject: [tied] Genetic Structure of a 2,500-Year-Old Human

Population

> in China ...

URL: http://groups.yahoo.com/group/cybalist/message/16575

> Genetic Structure of a 2,500-Year-Old Human Population in China and
> Its Spatiotemporal Changes
>
> Abstract
>
> To examine temporal changes in population genetic structure, we
> compared the mitochondrial DNA (mtDNA) sequences of three

populations

> that lived in the same location, Linzi, China, in different

periods:

> 2,500 years ago (the Spring–Autumn era), 2,000 years ago (the Han
> era), and the present day. Two indices were used to compare the
> genetic differences: the frequency distributions of the radiating
> haplotype groups and the genetic distances among the populations.

The

> results indicate that the genetic backgrounds of the three
> populations are distinct from each other. Inconsistent with the
> geographical distribution, the 2,500-year-old Linzi population

showed

> greater genetic similarity to present-day European populations than
> to present-day east Asian populations. The 2,000-year-old Linzi
> population had features that were intermediate between the present-
> day European/2,500-year-old Linzi populations and the present-day
> east Asian populations. These relationships suggest the occurrence

of

> drastic spatiotemporal changes in the genetic structure of Chinese
> people during the past 2,500 years.
>
> http://www.molbiolevol.org/cgi/content/full/17/9/1396

I've shifted this to the Nostratic list as I don't think it is of
much interest for Indo-European.

The 2,5000-year old population is based on 34 people, the 2,000-year
old population is based on 13 people, and the present-day population
on 50 people. Results from the 2,000-year old population must
therefore be used with extreme caution.

The paper tells us nothing about who the people in the 2,500-year old
population are, in particular, how closely related they are. If one
examines Figure 1 (click in the diagram), you will see that many of
the Group VI individuals had the same sequences. One sequence
occurred in 5 people (admittedly the ancestral sequence for Group
VI), another in 6 people, another in 3 people, and another two in 2
people. In this population, all the shared sequences are of Group
VI. It makes me think that members of the same family have been
sampled, which vastly reduces the statistical significance of the
results. Removing these 14 duplicates (not completely statistically
valid), Group VI drops from 22 out of 34 to 8 out of 20. The sample
still looks odd, but I think it then looks much more like present-day
Central Asian Turkic, not European.

Richard.