Thursday, December 11, 2008

A Growing Intelligence

IndiaBlitz and the Hindustan Times are reporting on a re-dating of the Ethiopian Gademotta site, which contains Middle Stone Age tools, containing blades and scrapers. The story states:

In the 1990s, for example, archaeologists dated a Middle Stone Age site in Ethiopia called Gademotta to 235,000 years ago, implying that the technology had been maturing for a while before the arrival of modern humans, although the accuracy of that dating has been questioned.

A second site, Kapthurin in Kenya, was more reliably dated in 2002 to 285,000 years ago, but researchers have been very reluctant to accept just one site as evidence that the Middle Stone Age started so early.

Both sites are in Africa's volcanic Rift Valley, the birthplace of many hominid species.

Now, according to a report in Science Now, two geochronologists from the University of California, Berkeley, Leah Morgan and Paul Renne, have redated Gademotta using the argon-argon method, an improved technique for dating volcanic rock that is considered more accurate than the potassium-argon method previously employed at the site.

The new results push the artifacts at Gademotta back to at least 280,000 years ago, essentially the same age as those at Kapthurin.

These two sites suggest that stone tool technology evolved continuously from Homo erectus/ergaster through early Homo sapiens to later archaic Homo sapiens, rather than in fits and spurts. It also suggests that there was more of a subtle transition between the different species of hominid.

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