Friday, February 5, 2016

What happened around 14,500 years ago?

We uncovered a completely unknown chapter of human history: a major population turnover in Europe at the end of the last Ice Age.

A European research team pieced together a piece of missing history by reconstructing the mitochondrial genomes of 55 hunter-gatherer individuals who lived in Italy, Germany, Belgium, France, the Czech Republic, and Romania 35,000 to 7,000 years ago.

Their results show that the mitochondrial DNA of three individuals who lived in present-day Belgium and France before the coldest period in the last Ice Age, the Last Glacial Maximum, belonged to haplogroup M, which was thought to be absent in modern Europeans but is extremely common in modern Asian, Australasian, and Native American populations.

This had previously led to the theory that non-African people dispersed on multiple occasions to spread across Eurasia and Australasia. The colleagues think that the discovery of this maternal lineage in Europe suggests instead that all non-Africans dispersed rapidly from a single population, at a time they place around 50,000 years ago. The M haplogroup disappeared from Europe when the Last Glacial Maximum began around 25,000 years ago. Hunter-gatherer populations retreated to the south into a number of putative refugia, and the resulting bottleneck caused the loss of this haplogroup.

The researchers say their biggest surprise, however, was evidence of a major turnover of the population in Europe around 14,500 years ago, as the climate began to warm. Our model suggests that during this period of climatic upheaval, the descendants of the hunter-gatherers who survived through the Last Glacial Maximum were largely replaced by a population from another source. The exact origin for this population is unknown, although the inferred demographic history  suggests that it descended from another, separate Last Glacial Maximum refugium.

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