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Saturday, April 12, 2014

Before the “Ice Age” - Research on Early Americans

Pullling Apart the Bering Strait Theory
Researchers here say they have unearthed stone tools proving that humans reached what is now northeast Brazil as early as 22,000 years ago. Their discovery adds to the growing body of research upending a prevailing belief of 20th-century archaeology in the United States known as the Clovis model, which holds that people first arrived in the Americas from Asia about 13,000 years ago.

Walter Neves, an evolutionary anthropologist at the University of São Paulo has done analysis of an 11,000-year-old skull in Brazil and implies that some ancient Americans resembled aboriginal Australians more than they did Asians.

Tom D. Dillehay, an anthropologist at Vanderbilt University, has shown that humans lived at a coastal site called Monte Verde as early as 14,800 years ago.

European and Brazilian archaeologists building on decades of earlier excavations said last year that they had found artifacts at a rock shelter showing that humans had arrived in South America almost 10,000 years before Clovis hunters began appearing in North America.

Dr. Guidon remains defiant about her findings. At her home on the grounds of a museum she founded to focus on the discoveries in Serra da Capivara, she said she believed that humans had reached these plateaus even earlier, around 100,000 years ago, and might have come not overland from Asia but by boat from Africa.

Genetic Evidence of a single migration (but not over Bering Strait)
The team’s work follows up on earlier studies by several of its members who found a unique variant (an allele) of a genetic marker in the DNA of modern-day Native American people. Dubbed the “9-repeat allele,” the variant (which does not have a biological function), occurred in all of the 41 populations that they sampled from Alaska to the southern tip of Chile, as well as in Inuit from Greenland and the Chukchi and Koryak people native to the Asian (western) side of the Bering Strait. Yet this allele was absent in all 54 of the Eurasian, African and Oceanian groups the team sampled. 

In these earlier studies, the researchers concluded that the most straightforward explanation for the distribution of the 9-repeat allele was that all modern Native Americans, Greenlanders and western Beringians descend from a common founding population. Furthermore, the fact that the allele was absent in other Asian populations most likely meant that America’s ancestral founders had been isolated from the rest of Asia for thousands of years before they moved into the New World: that is, for a period of time that was long enough to allow the allele to originate in, and spread throughout, the isolated population.