Tutu part Bushman, DNA shows

Researchers sequenced the complete genomes of five southern Africans over the age of 80 - Archbishop Desmond Tutu and four Bushmen from Namibia. This genetic peek deep into the heart of Africa confirms that Africans have more genetic diversity than Europeans or Asians and provides insights into how to live a long life despite disease and famine. 

"On average we found as many genetic differences between two Bushmen as between a European and an Asian," said Dr Vanessa Hayes of the University of New South Wales in Australia, who worked on the study reported in the journal Nature.

"This research now provides us with the tools to read the story of human evolution and specifically the story of disease evolution."

Geneticists have long known that, at the level of DNA, there is no such thing as race. They have also known that Africa, the source of all modern humans, also has more genetic diversity.

This is probably because so many different peoples stayed and evolved here, while Europeans, Asians and other groups arose from smaller populations that migrated from the continent.

Tutu and Bushman had different mutations

"To know how genes affect health we need to see the full range of human genetic variation, and Southern Africa is the place to look," said Webb Miller of Pennsylvania State University.

The team looked at some of the oldest Africans, both in terms of age and genetic roots. Tutu is an ethnic Bantu, while the four Bushmen all come from hunter-gatherer societies in the Kalahari desert of Namibia.

"The Bushmen participants have reached their advanced age despite living under harsh conditions due to periodic famine and untreated illness," the researchers wrote.

There were surprises. For instance, Tutu and one Bushman had many more different mutations known as single nucleotide polymorphisms or SNPs (pronounced "snips") than have been seen in sequencing other individuals.

They found differences in the genes that allow adults to digest cow milk, one related to having light-coloured skin, and SNPs that made all five men susceptible to malaria.

One of the Kalahari natives had a gene that reduces sweat loss, while four of the men had genes that give their bearers stronger bones.

These genes can all tell scientists how humans adapt to changing environments, the researchers said. They may also help in designing better drugs. Africans are often left out of trials for new drugs and researchers are finding more often that individual genes control how a person responds and reacts to drugs. - (Reuters Health, February 2010)