A recent paper provides some new, strong evidence for an origin of all
modern humans in Africa, going through a recent bottleneck.
Ke Y., Su B., Song X., Lu D., Chen L., Li H., Qi C., Marzuki S., Deka
R., Underhill P., Xiao C., Shriver M., Lell J., Wallace D., Wells R.S.,
Seielstad M., Oefner P., Zhu D., Jin J., Huang W., Chakraborty R., Chen
Z., Jin L., "African origin of modern humans in East Asia: a tale of
12,000 Y chromosomes", Science 292 (11 May 2001), 1151-1153, abstract:
"To test the hypothesis of modern human origin in East Asia, we sampled
12,127 male individuals from 163 populations and typed for three Y
chromosome biallelic markers (YAP, M89, and M130). All the individuals
carried a mutation at one of the three sites. These three mutations
(YAP+, M89T, and M130T) coalesce to another mutation (M168T), which
originated in Africa about 35,000 to 89,000 years ago. Therefore, the
data do not support even a minimal in situ hominid contribution in the
origin of anatomically modern humans in East Asia."
Furthermore, they write: "...no ancient non-African Y chromosome was
found in the extant East Asian populations (P = 5.4x10^-6 assuming a
frequency of 1/1000 of local contribution in the extant populations),
suggesting an absence of either an independent origin or a
1,000,000-year shared global evolution." ... "It has been shown that all
the Y chromosome haplotypes found outside Africa are younger than 35,000
to 89,000 years and derived from Africa" (95% confidence interval around
44,000 years). They deem extinction of archaic lineages due to genetic
drift unlikely: "...with 163 populations from different regions of Asia,
it is hard to imagine that all of the 163 populations should drift in
the same direction." Comparing Y chromosome and similar mitochondrial
data with the autosome and X chromosome estimates of 535,000 to
1,860,000 years for a common ancestor, they think "...this difference in
age estimation might only reflect the difference in the effective
population sizes between Y chromosome/mtDNA and X chromosome/autosome
(three to four times as many as the former) in the presence of
bottleneck events associated with the outbound migrations from
Africa..."
The case for an origin of all _modern_ humans in Africa (or the Middle
East?) with a bottleneck of a small (how large?) population a few ten
thousand years ago seems to tighten. Of course, this does not prove
anything about whether the earlier humans (like H.erectus,
H.heidelbergensis, Neandertal,...) were or were not of the same
_biological_ species (cross-fertile). Neither does it date Adam and Eve,
in my opinion. However, it makes it easier to conceive of the descent of
all modern humans from the first humans "created in God's image",
possibly to be dated at this bottleneck. This, however, is a very
tentative speculation.
Peter
-- Dr Peter Ruest, <pruest@dplanet.ch> CH-3148 Lanzenhaeusern, Switzerland Biochemistry - Creation and evolution ----------------------------------------------------------------- Creative providence in biology (Gen.2:3): "..the work which God created (in order) to (actively) evolve it" -----------------------------------------------------------------
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