DNA Diversifies Domestication's Roots

Article excerpt

Scientists generally trace the domestication of the wild ox, or aurochs, to about 10,000 years ago in ancient Turkey or nearby parts of southwest Asia. These beasts of burden then served as the founding population for modern cattle breeds throughout the world, the predominant theory holds. A new mitochondrial DNA study in living cattle breaks from the scientific herd on this issue.

Genetically discrete breeds of African, Asian, and European cattle existed 22,000 years ago or more, suggesting that domestication arose separately on each continent, assert Daniel G. Bradley, a geneticist at Trinity College in Dublin, and his colleagues.

The genetic findings lend support to the controversial proposal, advanced by Fred Wendorf of Southern Methodist University in Dallas and his coworkers, that cattle domestication emerged in northeastern Africa around 9,000 years ago, independent of any other domestications. At that time, summer rains in the eastern Sahara attracted seasonal occupations by herders, Wendorf argues.

"[Bradley's] article presents strong evidence that African domestic cattle have long been genetically separate from European and Asian cattle," Wendorf says. "Three centers of cattle domestication may have existed, with no crossbreeding of animals until sometime after 2,000 years ago."

The Irish researchers extracted mitochondrial DNA, which is inherited only through the mother, from blood samples of 90 living cattle in Africa, Europe, and India. …