美国科学60秒 SSS 2015-03-20（在线收听）

Feel to walk and in central Mexico is in archaeological site, a cultural landmark and tourist attraction best known for its pyramids and plaza. But nearly 2,000 years ago, it was a powerful urban center home to more than 100,000 people. It was also one of the best planned and most diverse of such pre-industrial cities because migrants of different ethnicity's streamed in followed the eruptions of two volcanoes in southern Mexico that made their own homes less desirable, and there's tale to a kind of stronger it attracted additional migrant work forces. This newcomers tended to serve as crafts people, construction workers, musicians and military personnel.Male researchers help to develop to mythology to study their remains of one multi-ethnic neighbourhood using * mythology, nutritional status and DNA along with other techniques, and may found that migrant groups appear to help them compete them among each other to obtain high status goods to manufacture items in demand by the city's leads. The study in the journal proceedings of the national academy of sciences. Study author Linda * of the * also points out that the city's rulers controlled the flow of all raw materials coming into tale to account. She further suggests that the lurk last immigrants competition with each other, the intermediate only giving economic power and ruling the leads control over raw materials may combine the contribute to the cultural attention that ultimately led to tail to all kinds of clubs. Sound familiar.