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Did Eve precede Adam?

New research on the very early origins of modern humans has turned up evidence that male and female humans as we know them today probably never met.

New genetic studies from Stanford University published in Nature Genetics reveal that the modern genetic form of women appeared far earlier than that of modern man.

Standford's Dr Peter Underhill and colleagues looked at genetic mutations over time in the Y chromosome - the gene which makes modern men who they are.

He found that our most recent paternal ancestors appeared about 59,000 years ago - 84,000 years after our maternal ancestors. Previous studies of mitochondrial DNA (inherited only from the mother) shows that our common maternal ancestors lived in Africa roughly 143,000 years ago.

The Stanford researchers analysed mutations in the Y chromosome, which occur over time and can be used as a kind of a clock. These chromosomes were examined in over 1000 men from 22 different ethnic groups. From the extent of these mutations, they worked backwards to build a family tree which traced back to a theoretical ancestor.

Obviously our ancestral mother did meet some form of man along the way. But Dr Underhill suggests these ancestral males had a different, less perfect version of the modern Y chromosome.

The work confirms the Out of Africa theory, which says humans evolved in Africa and began spreading into Asia and Europe about 44,000 years ago.

This research also has important implications for male fertility studies. The research team identified new molecular markers on the Y chromosome which could help pinpoint the genetic basis of problems in male fertility.

Dr Colin Groves from the School of Archaeology and Anthropology at the Australian National University said a common misunderstanding of mitochondrial DNA is that all people were descended from one women or a single man. "The individual was one of perhaps thousands of women and men alive at the time", he said.

He said it was possible that before humans moved out of Africa, the Y chromosome underwent a relatively sudden mutation which conveyed such a great advantage that it swept through the population and replaced all other types of mutations.

Tags: archaeology, cloning-and-dna, palaeontology