SSS 2012-06-20（在线收听）

 This is Scientific American 60 Seconds. I'm Cynthia Graber. This'll just take a minute. In Europe and the near east, people went from being mobile hunter gathers to more settled agriculture way of life. But in Africa, no matters domesticated animals long before they literally put down roots. Researchers know the history in part because of carve art in the Sahara. There are even drawings of full caw utters and the occasional scene of milking. But it's tough to reliably date the art or know how prevailing milking was. When researcher team studying human use of diary had experienced dating artifacts from Europe and Asia, they used their skills to analyze the 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 the Africans were engaged in dairy farming by about 7000 years ago. The study is in the journal Nature. Evidences of milk processing shows how dairying could have been quickly adopted even though the ability to digest lactose may have still been rare. The work should thus provide an additional data for evolutionary biologists studying lactose tolerance. A key genetic development in human history.