Thursday January 11 2:10 PM ET

Did We Come Out of Africa? Studies Collide

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - It seemed settled -- extensive genetic studies had
confirmed that the ancestors of all living humans emerged from Africa some
50,000 years ago and either killed off or out-competed all other human-like
creatures who settled across much of the world.

But two studies published this week strongly disputed this scenario and
reignited the vigorous and often acrimonious debate about where humans come
from.

One study, done in Australia, used genetic evidence that suggested ``Mungo
Man'' -- a 60,000-year-old skeleton -- is genetically unrelated to the
Africans believed to have evolved 150,000 or so years ago and later to have
settled the world.

Another, published in Friday's issue of the journal Science, analyzed
physical features of early human skulls to suggest there must have been
interbreeding among the migrating Africans and resident Neanderthals and
even Homo erectus species of pre-humans.

``There never was a marauding band of Africans,'' University of Michigan
anthropologist Milford Wolpoff, who with colleagues published the latest
report in Science, said in a telephone interview.

Replacement Theory Said Wrong

Wolpoff said his findings and the Australian findings indicated humans in
Europe and Australia evolved gradually from Homo erectus and Neanderthals,
with input from Africans, over time. This view contrasted with theories
that Homo erectus and Neanderthals were dead-end species.

``It certainly means that the ``Eve'' theory, the replacement theory, seems
to be wrong,'' Wolpoff said.

He argued there is no such thing as a separate species of early humans,
despite studies of Neanderthal DNA that showed it to be distinct from the
DNA of modern living humans.

``Ancient humans shared genes and behaviors across wide regions of the
world, and were not rendered extinct by one 'lucky group' that later
evolved into us,'' Wolpoff said.

``The fossils clearly show that more than one ancient group survived and
thrived.''

Studies released in November 2000 seemed to reinforce the idea that one man
who lived in Africa 59,000 years ago and one woman who lived some 143,000
years ago are the genetic ancestors of all surviving humans.

Peter Underhill of Stanford University in California and colleagues around
the world did a genetic analysis of DNA samples from the Y chromosomes of
more than 1,000 men, and mitochondrial DNA from women, to reach their
conclusion.

Both types of DNA are believed to be passed down from father to son in the
case of Y chromosomes, and mother to daughter in the case of mitochondrial
DNA, with relatively few changes that can be ``clocked'' with each
generation.

Groups Must Have Intermixed

Wolpoff did not dispute these findings but strongly disagreed with the idea
that they meant modern Africans killed or out-competed earlier human
populations, replacing Neanderthals and Homo erectus 50,000 to 60,000 years
ago.

``Whenever we come into contact with other people, we share genes,''
Wolpoff said. ``It is obvious to us that the groups must have
intermixed.''

For its study Wolpoff's group examined fossil skulls from the Mladec cave
in the Czech Republic and a skull from the Willandra Lakes region of
Southeastern Australia.

``We looked at crania,'' Wolpoff said. ``If you are digging a basement for
your house and up came a skeleton and you called in a local forensic
scientist, they would go right to the skull. The cranium is the most
diagnostic part.''

The researchers compared bumps from the cranium of the Australian fossil to
skulls of Homo erectus skeletons from Indonesia. The Czech skulls were
Neanderthal and were compared with samples from the Middle East.

``The data imply that both have a dual ancestry,'' they wrote in their report.

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