Human populations expanded before agriculture: study

When did human beings first begin to rapidly spread around the globe? According to a new genetic analysis published Thursday, it was more than 10,000 years ago -- before agriculture took hold.

Lines of evidence from linguistics and anthropology have led many researchers to argue that agriculture allowed humans to spread more rapidly and widely than ever before because of the increased food security it provided.

But genetic analyses that use the DNA of people alive today to trace population origins have often been contradictory, in part because genomic data itself has not been randomly collected from people around the world -- a necessary precondition that allows scientists to accurately model where people came from, and when.

The new study, conducted by a group of Chinese scientists and published in the journal Scientific Reports, uses data from the 1,000 Genome Project. They analyzed the DNA from 910 samples from 11 different groups in Africa, Europe and the Americas.

Across the three continents and the 11 groups, the researchers found that most of the rapid population expansions actually occurred before the advent of agriculture, in a period called the Late Glacial Maximum. That period was marked by a relatively warm and mild climate, and it followed a period of intense cold when ice sheets covered much of the planet.

Given the timing, it appears the expansion of human populations was mostly driven by a warming climate, which converted previously frozen land into livable terrain.

That process probably was accelerated once agriculture began in earnest, the authors write.

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