The human population at that time was reduced to small isolated
groups in Africa, apparently because of drought, according to an
analysis by researchers at Stanford University.
The estimated the number of early humans may have shrunk as low as
2,000 before numbers began to expand again in the early Stone Age.
“This study illustrates the extraordinary power of genetics to reveal
insights into some of the key events in our species’ history,” Spencer
Wells, National Geographic Society explorer in residence, said in a
statement. “
Tiny bands of early humans, forced apart by harsh environmental
conditions, coming back from the brink to reunite and populate the
world. Truly an epic drama, written in our DNA.”
Wells is director of the Genographic Project, launched in 2005 to study
anthropology using genetics. The report was published in the American
Journal of Human Genetics.
The migrations of humans out of Africa to populate the rest of the
world appear to have begun about 60,000 years ago, but little has been
known about humans between Eve and that dispersal.
The new study looks at the mitochondrial DNA of the Khoi and San people
in South Africa which appear to have diverged from other people between
90,000 and 150,000 years ago.
The researchers led by Doron Behar of Rambam Medical Center in Haifa,
Israel and Saharon Rosset of IBM T.J. Watson Research Center in
Yorktown Heights, N.Y., and Tel Aviv University concluded that humans
separated into small populations prior to the Stone Age, when they came
back together and began to increase in numbers and spread to other
areas.
Eastern Africa experienced a series of severe droughts between 135,000
and 90,000 years ago and the researchers said this climatological shift
may have contributed to the population changes, dividing into small,
isolated groups which developed independently.
Paleontologist Meave Leakey, a Genographic adviser, commented: “Who
would have thought that as recently as 70,000 years ago, extremes of
climate had reduced our population to such small numbers that we were
on the very edge of extinction.”
Today more than 6.6 billion people inhabit the globe, according to the
U.S. Census Bureau.
Posted by Casey Kazan.
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