SSS 2009-08-14
时间：2019-01-08 作者：英语课 分类：Scientific American(八)月
- 1 SSS 2009-08-14
Early modern humans didn’t just chip away at stones to create their tools. They treated stone with fire in a sophisticated fashion, according to research published August 14th in the journal Science.
About 72,000 years ago, our ancestors along coastal 1 South Africa made tools from silcrete, a cement-like layer of soil. The silcrete found at archaeological sites was glossy 2 with a fine grain and a reddish color. It didn’t match stones in local outcroppings. Researchers from the University of Cape 3 Town couldn’t find big enough pieces to learn more, until a couple of years ago. Then a colleague from Arizona State University remarked that a piece of silcrete reminded him of heat-treated tools in the Southwest.
So the researchers set up a fire pit and buried a silcrete sample at high temperature. The next day, the stone looked like ones used by early humans. It flaked 4 easily and provided the basic material for complex tools. Until now, heat treatment was thought to have started in Europe 25,000 years ago. This discovery pushes it back tens of thousands of years into Africa—and suggests that the southern African coast may have been the site of a truly Promethean revolution.
- The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
- This country will fortify the coastal areas.该国将加强沿海地区的防御。
- I long for a trip to the Cape of Good Hope.我渴望到好望角去旅行。
- She was wearing a cape over her dress.她在外套上披着一件披肩。