By Marlowe Hood (AFP) – Feb 17, 2010
PARIS — Scientists said Wednesday they had sequenced the genome of Bushmen, the longest-surviving lineage of modern humans, expanding our understanding of genetic diversity and inherited disease.
Comparison of DNA provided by a Bushman elder and South African Archbishop Desmond Tutu showed that Tutu is partly of Bushman heritage, they added.
The 78-year-old Nobel winner voiced "astonishment and delight" at the news, a researcher told AFP.
Bushmen is the collective term for linguistically-distinct groups of hunter-gatherers who inhabit the Kalahari Desert, which straddles parts of Botswana, Namibia and South Africa.
They are the oldest known continuous community of modern Homo sapiens, having lived in this sparsely-populated region for some 27,000 years.
The genomes substantially widen knowledge about humanity's book of life, revealing our species to be more genetically diverse than thought, the investigators said.
"We have been able to add an enormous amount of information to the genome database," said Vanessa Hayes, a cancer specialist at the University of New South Wales, Australia and co-leader of the study.
"There are 1.3 million genetic variants that had never been reported before," she said by phone from Namibia.
Hayes said the findings -- appearing in the journal Nature on Thursday -- will help balance a "eurocentric" focus in genomics.
"As a result of this project, southern Africans will immediately be included in genome-wide association studies, increasing our ability to examine regionally significant diseases," she said.
Before this study, only nine individual human genomes had been fully sequenced. The majority are of European heritage, with the others coming from China, Korea and the Yoruba people of Nigeria.
Tutu was invited to participate in the study, in part because his mixed heritage brought together the region's rich ethnic diversity, said Hayes.
"Having a Tswanta mother and a Nguni-speaking father means his ancestry covers the two linguistic groups ... that represent about 90 percent of all Bantu is southern Africa," she said.
Bantu includes hundreds of ethnic groups in sub-Saharan Africa that speak a variety of languages as diverse as those covering the Indo-European family.
Tutu "was very proud to learn" that he had Bushman genes, said Hayes.
He was also tapped to help deliver a message of genome justice.
"Indigenous people have been left out of medical research efforts based on genetics," she said.
Tutu has in the past ardently defended the rights of Bushmen, many of whom have been pushed into resettlement as their ancestral lands have been increasingly taken over by neighboring populations.
What was especially surprising, though, was that Bushmen are very diverse genetically and this diversity falls along linguistic lines.
If you compare two people of European origin anywhere in the world, their gene profiles will "basically fall right on top of each other," Hayes said.
"But between two different Bushmen linguistic groups, they will be more different from each other than a European and an Asian. That is incredible," she said.
The genetic profiles also showed how the hunter-gatherers adapted to their foraging lifestyle and harsh environment, the study found.
Bushmen are likelier to have muscle genes that confer sprint performance, as well as a gene variation enabling them to taste bitter compounds, helping them as hunter-gatherers to spot plants with toxic fruits.
But their genetic isolation has also put them in danger.
The fact, for example, that they have lived for millennia in an arid environment means they never evolved genes offering some protection against malaria, as have many other human populations living in wetter climes.
As malaria-spreading agriculture practices encroach on their homelands, "the question is will they have enough time to adapt to it and are there enough bushmen left to be able to withstand the disease," said Hayes.
Estimates of their numbers run generally from 70,000 to 100,000.
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