A group of hunters from the Ju/'hoansi tribe in the Namibian Bush. Credit: Stephan C. Schuster

The pool of complete human genome sequences just got a bit bigger, thanks to the addition of two men from southern Africa; Archbishop Desmond Tutu, the South African civil-rights activist, and a man named !Gubi, from a Khoisan community in Namibia. Researchers also analyzed partial genomes of three other members of the Khoisan, a collection of hunter-gathererer groups in the Kalahari desert that makes up one of the world's oldest and most diverse populations. Tutu is Bantu, a group that makes up the majority of the population in southern Africa.

The majority of complete genome sequences to date have come from men of European descent, including scientists James Watson, George Church, and Stephen Quake. But analyzing diverse groups is important for both medical and scientific reasons. People in Africa are known to have high levels of genetic diversity--because the human species originated there, genetic variations have had more time to accumulate.

In the new study, published today in the journal Nature, researchers found that the four Khoisan men are as genetically different as a European and an Asian person. "This is despite the fact that they sometimes live within walking distance of one another," team leader Stephan Schuster, a genome researcher at the Pennsylvania State University, told Nature. According to the article, "!Gubi's and Tutu's genomes each carry more than one million single base-pair changes that are not found in each other or in any of the published genomes, including one from a Yoruba individual from West Africa."

Researchers "found single nucleotide polymorphisms related to enhanced physical prowess," according to a statement from Baylor College of Medicine, which participated in the research. "For example, four had two copies of a gene associated with higher bone mineral density and strength. Three had two copies of a gene associated with increased sprint and power performance. One desert dweller had a gene for a chloride channel (a tiny pore in the cell membrane that allows ions in and out) that enables the person to retain salt and water--an advantage in people in dry climates."

The findings could have important medical implications for people of African descent. According to Nature,

The continent's rich genetic diversity means that some drugs designed to treat Europeans do not work well in Africans. And genome-wide association studies designed to trace the genetic underpinnings of disease are difficult to execute in Africa because the arrays used to detect genetic variation were designed using mostly European sequences. As a result, researchers lack the tools to study important medical mysteries, such as why the Khoisan and some other African populations are particularly susceptible to tuberculosis.