Saturday, May 19, 2001

Mungo Man or out of Africa? It's in the genes

By Deborah Smith, Science Writer

A genetic study of more than 12,000 Asian men, living as far apart as Iran and Papua New Guinea, shows they are all descended from African men who lived 35,000 to 90,000 years ago.

The research strongly supports the Out-of-Africa theory of evolution - that modern humans emerged in Africa about 100,000 years ago, and then spread around the globe.

The migrating Africans did not interbreed with archaic humans already living in Asia, such as Peking man and Java man, the international team, led by Dr Li Jin of Fudan University in China, said.

The genetic results "indicate that modern humans of African origin completely replaced earlier populations in East Asia", they reported in the journal Science.

The Herald revealed earlier this month that European scientists had questioned an Australian team's claim to have extracted ancient DNA from a 60,000-year old fossil known as Mungo Man.

Australian team leader, Dr Alan Thorne, of the Australian National University, has argued that Mungo Man's DNA supports the competing Regional Continuity theory. This holds that modern humans evolved from archaic humans during the past million years, with interbreeding between regional groups.

Some of the strongest evidence for this multi-regional theory has come from fossils in Asia. But now the genetics of people from the region tell a different story.

The latest study examined the Y chromosome of men from 163 different populations in India, Siberia, East Asia, China, Taiwan, Indonesia and the South Pacific islands. The Y chromosome, which only men have, is passed unchanged from father to son.

The researchers looked for three specific mutations. Every one of the 12,127 men tested had at least one. Previous research has shown the three mutations are derived from an earlier mutation that arose in African men between 35,000 and 89,000 years ago. Absence of all three mutations would have indicated the man could have had some more ancient ancestors, they said.

A member of the Australian Mungo Man team, Dr Lars Jermiin, of the University of Sydney, said the results were interesting, but he questioned some of the team's interpretation. He said more of the 3 billion letters in the human genome needed to be studied to fully understand our origins.