Long-lost lake may have helped humans out of Africa
Long-lost lake may have helped humans out of Africa
18:26 17 January 2014 by Jeff Hecht
A giant, long-vanished lake along the White Nile may have been a vital way station for early modern humans leaving Africa. Archaeologists say the 45,000-square-kilometre lake, which would be one of the ten largest lakes on Earth if it existed today, was in the right place at the right time for at least one of two key migrations. One exodus took people to what is now Israel before 100,000 years ago, and another peopled Eurasia 70,000 years ago.
Geologists had seen traces of an ancient lake in the now-arid region south of Khartoum in Sudan, but it was too old for carbon dating so they didn't know when it dried up. So Martin Williams of the University of Adelaide in Australia teamed up with Tim Barrows of the University of Exeter, UK, to try other dating techniques. The two collected samples from former lake-shore deposits, and Barrows dated them to around 109,000 years ago.
Barrows and Williams traced the long-lost freshwater lake along some 650 kilometres of the White Nile, one of the two main tributaries to the Nile. At points, the lake seems to have stretched to almost 80 kilometres wide.
Its peak extent came in the last interglacial period, a warm interval before the last ice age. Barrows says it cannot have stayed at full size for long, because the lake-shore deposits he found took "thousands of years to form, but probably not tens of thousands". His dating techniques measure how long it has been since the deposits were exposed, so his date tells us when the lake first began to shrink.
More:
http://www.newscientist.com/article/dn24893-longlost-lake-may-have-helped-humans-out-of-africa.html?cmpid=RSS|NSNS|2012-GLOBAL|online-news#.UttQC2fnbmI
