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Author Topic: Mapping Human Genetic Diversity in Asia  (Read 1151 times)
Charlie Hatchett
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Posts: 101

« on: December 13, 2009, 02:55:07 PM »

“…Our results show that genetic ancestry is strongly correlated with linguistic affiliations as well as geography.
Most populations show relatedness within ethnic/linguistic groups, despite prevalent gene flow among populations…”

“…More than 90% of East Asian (EA) haplotypes could be found in either Southeast Asian (SEA) or Central-South Asian (CSA) populations and show clinal structure with haplotype diversity decreasing from south to north. Furthermore, 50% of EA haplotypes were found in SEA only and 5% were found in CSA only, indicating that SEA was a major geographic source of EA populations…”

“…we concentrated on uncovering the geographic source(s) of EA and SEA populations…”

“…At K = 4, a component most frequently found in Negrito populations that is also shared by all SEA populations emerges, suggesting a common SEA ancestry…”

“…These observations suggest that SEA and EA populations share a common origin…”

“…The geographic source(s) contributing to EA
populations have long been debated. One hypothesis
suggests that all SEA and EA populations
derive primarily from a single initial migration,
which entered the continent along a southern,
largely coastal route (19, 20). Another hypothesis
argues for at least two independent migrations
into East Asia, first along a southern route, followed
later by a series of migrations along a more
northern route that served to bridge European and
EA populations, but with little contribution to
populations in Southeast Asia…”

“…The superior association between genetic
distance and the group indicator matrix as measured
by the correlation coefficients suggests that
prehistorical population divergence is the favored
model over IBD in explaining the data (24). This
conclusion is supported by simulation studies that
also suggest that the observed patterns cannot be
explained by simple IBD effects alone…”

“…The IBD model predicts a correlation of genetic
distance with geographical distance but not genetic
diversity and geographic distance (24). By
contrast, we found (Fig. 3A) that haplotype diversity
is strongly correlated with latitude (R2 =
0.91, P < 0.0001), with diversity decreasing from
south to north, which is consistent with a loss of
diversity as populations moved to higher latitudes.
In estimating the contribution of SEA and
Central-South Asian (CSA) haplotypes to the EA
gene pool by haplotype sharing analyses (16), we
found that more than 90% of haplotypes in EA
populations could be found in SEA and CSA populations,
of which about 50% were found in SEA
and EA only and 5% found in CSA only…”

“…Phylogenetic analysis of private
haplotypes indicates greater similarity between
EAand SEA populations relative to EA and
CSA populations (Fig. 3C). These observations
suggest that the geographic source(s) contributing
to EA populations were mainly from SEA populations,
with rather minor contributions from CSA
and that this clinal structure of EA populations
arose from prehistoric population divergence rather
than IBD or gene flow from CSA populations.…”

“…Our forward-time
simulation results under extreme ascertainment
scenarios (SOM text) show that the observed phylogeny
is not the result of ascertainment bias.
Simulation studies also suggest that substantial
levels of migration between populations after
their initial separation are unlikely to distort the
topology of the phylogeny…”

“…the evidence from our autosomal data
and the accompanying simulation studies (figs.
S29 and S30) point toward a history that unites the
Negrito and non-Negrito populations of Southeast
and East Asia via a single primary wave of entry
of humans into the continent…”
Charlie Hatchett

PreClovis Artifacts from Central Texas

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