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Ladywriter

Bottlenecks made humans less diverse

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Study suggests genetic diversity limited by two sudden population declines

Now, a recent study from University of Cambridge researchers William Amos and J.I. Hoffman suggests that the limited genetic diversity we see among humans today came from two major evolutionary bottlenecks — or sudden declines in population — that lead to a loss of genetic diversity. Amos and Hoffman found evidence of these events after they examined genetic samples from 53 distinct world populations. In the study, published in the October Proceedings of the Royal Society: B, the pair studied the frequency of two genetic indicators.

When Amos and Hoffman examined their samples, they found evidence of a bottleneck outside of Africa around 50,000 years ago. They also found a second major evolutionary bottleneck that occurred somewhere around the Bering land bridge, a narrow strip of land now submerged beneath the Bering Strait, which many anthropologists believe humans used to populate the Americas from Eurasia.

It's tempting to imagine sudden declines in human population at the hands of saber-toothed tigers or from a massive comet strike, but Amos says the likelier scenario is that humans diverged from one large population over and over again, leading to a series of what are known as founder effects. As humans leave big groups for smaller ones, they carry with them only a sample of the genes found in the larger group.


                                               gallery_3_22_21209.jpg

                                               Look at the flowers

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well....

most people in Italy are Italian....

Americans are well mixed :P


                                               gallery_3_22_21209.jpg

                                               Look at the flowers

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