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Archiver > GENEALOGY-DNA > 2002-09 > 1031171225


From: Mark May <>
Subject: RE: [DNA] Toba bottleneck
Date: Wed, 4 Sep 2002 15:28:27 -0500


Thanks Grant, you are absolutely correct that this idea has been suggested
and published. Here is another link with more info on his theory.

http://www.bradshawfoundation.com/evolution/

It would seem that he is looking at DNA data that suggests a bottleneck and
looking for an explanation. Also he wants to explain racial
characteristics. Toba does not seem to be a very good explanation for any
of this without evidence of other mass extinctions. Also I think that
since 1998 when this was published the experts have pushed back the Out of
Africa for Homo Sapiens to 100-120 KA, to account for new discoveries like
Lake Mungo, and haven't they pushed back the time for the postulated
bottleneck as well?

I would say his theory does not account for a number of facts very well,
which is probably why it hasn't gotten much play in the past few years.

Lake Mungo, by the way, as discussed on this list recently, is a problem
for any bottleneck theory, as it shows mtDNA unlike any modern population
in 60 KA fossils.


J Mark May

-----Original Message-----
From: [SMTP:]
Sent:Wednesday, September 04, 2002 2:25 PM
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Subject:[DNA] Toba bottleneck

In a message dated 9/4/02 11:26:41 AM Pacific Daylight Time,
writes:

> I have never heard of this explanation for the bottleneck before, and I
> consider it highly unlikely. Please cite a source for Toba wiping out
the
> human race.

I don't know how likely it is but the theory was published in the June 1998
issue of the Journal of Human Evolution.

Late Pleistocene human population bottlenecks, volcanic winter, and
differentiation of modern humans
Stanley H. Ambrose
Journal of Human Evolution, Vol. 34, No. 6, Jun 1998, pp. 623-651 (doi:
10.1006/jhev.1998.0219)

Past Effects of Volcanic Eruptions
Toba Bottleneck

Approximately 71,000 years ago a horrific volcanic winter was brought on by
the eruption of Mount Toba in Sumatra. This volcanic winter followed by the
coldest 1,000 years of the Last Ice Age caused massive death and famine to
modern human and animal populations throughout the world. The results of
the
super-eruption of Toba may have also been a "bottleneck" in the evolution
of
modern humans. A "bottleneck" is an abrupt decrease in population,
followed
by rapid "differentiation" - or genetic divergence - of the surviving
populations. Anthropologist Stanley Ambrose of the University of Illinois
proposes that a volcanic winter reduced human populations to "levels low
enough for evolutionary changes, which occur much faster in small
populations, to produce rapid population differentiation," Ambrose said.
If,
as he believes,the eruption of Mount Toba in Sumatra caused the bottleneck,
"then modern human races may have diverged abruptly, only 70,000 years
ago,"
Ambrose wrote in the June (1998) issue of the Journal of Human Evolution.

Grant

"The nice part about living in a small town is that when you don't know
what
you're doing, someone else does." -- Unknown,











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