成人快手

Archaeologists have faced a mysterious gap in the story of the first human occupants of North America. Native Americans split from their relatives in Siberia roughly 25,000 years ago but they only appeared in Alaska 15,000 years ago, leaving an unexplained gap of 10,000. One theory is that humans may have spent the time in between taking refuge on the Bering Land Bridge between Russia and Alaska. Today, this region lies under water but new analyses of deep sea sediment cores reveal that the land bridge back then was covered by shrub tundra. This would have enabled the settlers to light fires and burn large mammal bones to survive the freezing temperatures. Professor Scott Elias from the University of London has reviewed the evidence.

Indus Megacity Collapse
Four thousand years ago - at roughly the same time as the great pyramids of Egypt were being constructed - people of the Indus civilisation in India and Pakistan lived in beautifully elaborate megacities. But shortly after, these urban centres were abandoned and their civilisation collapsed. New research suggests that climate change could be a key reason. University of Cambridge archaeologist Dr Cameron Petrie explains how scientists have demonstrated an abrupt weakening of the summer monsoon and a resulting drought at that time from looking at snail shells.

American Physical Society Meeting
Huge, geoengineering projects to tame wind patterns circulating the globe as a way to protect the US from extreme weather; that is only one of the topics that the top minds of physics discussed at the American Physical Society Meeting during this week. Our reporter James Morgan went to the conference in Colorado, in the US and tells us more about what happens when you put together 9,000 physicists together for a week.

(Photo: Shrub tundra in Alaska, which is the kind of vegetation the researchers think, covered the Bering Land Bridge during the last Ice Age. Courtesy of Royal Holloway, University of London)