http://www.newscientist.com/news/news.jsp?id=ns9999307
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A man who died about 60,000 years ago in Australia could force a rethink of
our theory of human origins.
Researchers in Australia have accomplished the extremely difficult feat of
extracting DNA from his skeleton and were astonished to find the sequence is
unique, matching nothing seen before.
The DNA is the oldest ever recovered from human remains. It shows that while
the man is completely anatomically modern, he came from a genetic lineage
that is now extinct. This finding challenges the prevailing theory that all
modern humans are descended from a group of people who migrated from Africa
around 100,000 years ago.
"It's remarkable - totally unpredicted," says anthropologist Alan Mann of
the University of Pennsylvania.
Alan Thorne of the Australian National University in Canberra, who led the
new research, says: "A simplistic 'Out Of Africa' model is no longer
tenable."
But not all experts agree. "The genetic evidence is equivocal," says Colin
Groves, of the ANU. "The African origin model stands or falls by the fossil
evidence. In my opinion, it stands."
The new research contradicts a recent study of mitochondrial DNA, which
supported the Out of Africa theory (New Scientist online, 6 December 2000).
The remains of Mungo Man were found on the shores of Lake Mungo in
south-eastern Australia in 1974.
In 1995, a team led by Thorne began an attempt to extract genetic material
from the remains. Gregory Adcock and his colleagues at CSIRO Plant Industry
managed to replicate and sequence a single gene from Mungo Man's
mitochondria. The small genome of these cell powerhouses is passed down the
female line.
Simon Easteal, an evolutionary geneticist at ANU, then set about analysing
the sequence and comparing it with sequences of the same gene from nine
other early Australians - ranging in age from 8,000 to 15,000 years - as
well as 3,453 contemporary people from around the world, chimpanzees,
bonobos and two European Neanderthals.
According to Easteal's evolutionary tree, the line that led to the most
recent common ancestor of contemporary people, includes the ancient
Australians but excludes Mungo Man.
"We can say with a high degree of confidence that modern people arrived in
Australia before the new lineage [of the most recent common ancestor]
arrived," Easteal says.
The findings are due to be published in the online edition of the
Proceedings of the National Academy of Sciences.
For more on the DNA study of Mungo Man, see the 13 January issue of New
Scientist magazine.