From: Ephrem Tekle (ephrem@dehai.org)
Date: Thu Apr 12 2001 - 15:52:54 EDT
By Patrica Reaney (Reutors)
After studying the genetic ancestry of 53 people from different
continents and populations, Swedish scientists say all human ancestors
come from African ancestors that migrated from the continent about
52,000 years ago. (Corbis)
L O N D O N, Dec. 6 ‹ The ³Out of Africa² theory that modern man
evolved there and spread across the world got a boost today with new
research tracing humans from diverse ethnic and geographical
backgrounds back to that continent.
Swedish scientists used mitochondrial DNA ‹ genetic material in a
cell that is passed unchanged from mother to child ‹ from 53 people to
show that the human evolutionary tree is firmly rooted in Africa.
End of the Evolution Controversy? ³This is the first study in which
the genome is being used in a sufficiently large number of individuals
to come up with very strong evidence, in this case supporting the ŒOut
of Africa¹ theory,² Professor Ulf Gyllensten said in a telephone
interview. The biologist and geneticist at the University of
Uppsala said that even scientists who believe modern humans evolved
simultaneously in several parts of the globe would now have to
acknowledge that humans originate largely from Africa. ³It could
be the end of the argument so far that there is an African origin,²
Gyllensten added. Gyllensten and his colleagues traced the
ancestry of 53 people from DNA blood samples that were used in another
scientific study. The people came from different continents and
populations. Because mitochondrial DNA is inherited only via the
mother, it is a good way to trace genetic lineage.
Earlier Migration From Continent The results, which are published in
the science journal Nature, show that all the people tested have
origins in Africa and that the migration from the continent began
52,000 years ago, not 100,000 years ago as was previously thought.
³Our results point to something around 52,000 years ago. Other
estimates have pointed to 100,000 years ago but I think we have more
accurate information,² according to Gyllensten. In a commentary
on the research in Nature, S. Blair Hedges of Pennsylvania State
University described the Swedish research as the most thorough
analysis yet of divergences in human mitochondrial DNA. ³The
upshot is a robust tree rooted in Africa, which times the exodus from
Africa to within the past 100,000 years. With this result, the
pendulum swings further towards the claim that modern humans, Homo
sapiens, originated in Africa,² Hedges said. He added that the
evolutionary tree, which has more data than similar studies, indicates
that some Africans are closer to Europeans and Asians than to other
Africans.
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