Archbishop Desmond Tutu in genome health study

By Doreen Walton
Science reporter, BBC News

Archbishop Tutu's complete genome has been sequenced and published

Scientists have analysed the genomes of five southern Africans, including Archbishop Desmond Tutu, to study their genetic diversity and health.

The research, published in the journal Nature, compared genes of the Archbishop with San people.

"I am excited by the results," Archbishop Tutu told BBC News.

"Without these tests, I would not have known my bloodline... I am related to the San people, the first people to inhabit Southern Africa," he explained.

Archbishop Tutu is a Bantu, traditionally an agricultural people, and said he was related to the San, who have traditionally lived around the Kalahari desert of southern Africa, through his mother.

"The fact that the test found that I am related to these wise people who paint rocks makes me feel very privileged and blessed."

"Archbishop Tutu, through his Tswana and Nguni Ancestry, is an ideal representative for most southern Africans," said co-author Vanessa Hayes from the University of New South Wales, Australia.

The team of researchers from Africa, America and Australia hope that the study will help redress the geographic imbalance in disease susceptibility studies based on genetics.

It would be disastrous if scientists were to ignore the diversity of the human race because this is the greatest asset of humanity Archbishop Desmond Tutu

Southern Africans have often been poorly represented in drug trials and it will now be possible to include them in genome based studies on disease.

The Archbishop says he was sceptical at first but believes the study will directly benefit southern Africans. "Initially I was not sure what the DNA test would prove but was willing nonetheless to go through with the project," he said.

"Genetic information is important for pharmaceutical companies in preparation of drugs and it is for that reason among others that I agreed to participate in this research."

All the participants were around 80 years old so long health records were also available for the scientists to study in conjunction with the genetic information.

Archbishop Tutu has had cancer and said he was relieved at what the genome study told him about his personal health. "The test revealed that although I have had TB and cancer, there were no genetic diseases and that gave me immense relief," he told the BBC News website.

Geographic diversity

As well as the Archbishop, four indigenous hunter-gathers living in different parts of the Kalahari took part, all of them tribal elders.

The San people of the Kalahari are hunter-gatherers

The researchers say knowledge of their genetics is important in understanding the DNA of all other peoples because the Bushmen are the oldest known lineage of modern human.

The African continent is the most genetically diverse place on Earth, and the region from which all modern humans originate.

The study found that southern Africans were genetically quite distinct from Europeans, Asians and West Africans. The diversity among the San people was particularly striking.

"On average, there are more genetic differences between any two [San] in our study than between a European and an Asian," explained Professor Webb Miller from Pennsylvania State University in the US, who compared the genomes.

"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."

Science explained: What is a genome?

Some of the individual genes identified in the San were found to relate to their lifestyle and diet. An allele associated with light coloured skin and one related to digestion of milk were not found.

An African specific malaria resistance allele was also not found. The Kalahari Desert is largely malaria-free and the researchers say the lack of this gene could be significant if the Bushmen were forced into a farming lifestyle which could bring increased exposure to disease.

Four of the elders had genes linked with higher bone mineral density and strength; three had genes associated with a better ability to sprint; one of the men who lived in the desert had a gene which allows reabsorption of chloride ions which could help with salt and water retention.

Another genetic trait found was the ability to taste bitter compounds, which could help hunter gatherers avoid toxic plants.

Archbishop Desmond Tutu said the results of the study were important for everybody, not just southern Africans. "It is exciting that science is finding evidence of genetic diversity among groups of people as well as among individuals and this discovery should be embraced, not feared," he said.

"It would be disastrous if scientists were to ignore the diversity of the human race because this is the greatest asset of humanity."