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From:
Subject: [DNA] Toba bottleneck
Date: Wed, 4 Sep 2002 15:24:52 EDT


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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