非洲7千年前就养奶牛

In Europe and the near East, people went from being mobile hunter-gatherers to a more settled agricultural way of life. But in Africa, nomads domesticated animals long before they literally put down roots.

Researchers know this history in part because of cave art in the Sahara. There are even drawings of full cow udders and the occasional scene of milking. But it's tough to reliably date the art, or know how prevalent milking was.

One research team studying human use of dairy had experience dating artifacts from Europe and Asia. They thus used their skills to analyze a site in the Libyan Sahara.

The scientists studied 81 pottery shards. All the pieces had some residue of animal fat. The researchers analyzed the chemical compounds and were able to determine that Africans were engaged in dairy farming by about 7,000 years ago. The study is in the journal Nature. [Julie Dunne et al., "First dairying in green Saharan Africa in the fifth millennium B.C."]

Evidence of milk processing shows how dairying could have been quickly adopted, even though the ability to digest lactose may still have been rare. The work should thus provide additional data for evolutionary biologists studying lactose tolerance, a key genetic development in human history.

—Cynthia Graber