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Researchers at Cornell University have developed new statistical methods based on the complete genome sequences of living humans to shed light on events at the dawn of human history.
The scientists applied their methods to the genomes of individuals of East Asian, European, and western and southern African descent.
Although they analyzed just six genomes, the researchers made use of the fact that these genomes contain traces of genetic material from thousands of human ancestors, which have been assembled into new combinations over the millennia by genetic recombination.
The primary finding of the study is that the San, an indigenous group of hunter gatherers from southern Africa, diverged from other human populations about 130,000 years ago - earlier than previously thought. By comparison, the ancestors of modern Eurasian populations migrated from Africa only about 50,000 years ago.
Previous studies of human demography have primarily relied on mitochondrial DNA from the maternal line or Y-chromosome data passed from fathers to their sons. However, those studies were limited by small numbers of genomic positions.
The current study uses the full genome of each individual, providing a more comprehensive view of human evolution, the researchers said.
"The use of genomewide data gives you much more confidence that you are getting the right answer," said Adam Siepel, associate professor of biological statistics and computational biology, and senior author of the paper.