A cataclysmic meteor impact in Canada may have been the catalyst that triggered the start of civilisation.
Evidence indicates an asteroid or comet struck Quebec around 12,900 years ago.
Scientists believe the impact caused a transition to a colder, drier climate around the world which had far-reaching effects.
In North America, big animals including mastodons, camels, giant ground sloths and sabre-toothed cats all vanished, while their human hunters turned to a subsistence diet of roots, berries and smaller game.
Meanwhile thousands of miles away in the eastern Mediterranean, the first farmers started growing cereals. The invention of agriculture was a pivotal step in the development of large settled communities and civilisation.
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Experts agree on the climate change that marked the start of the Younger Dryas period, but are divided about its cause. The new research is said to provide "conclusive" evidence that the trigger was a meteor impact.
Before now the most popular explanation has been an ice dam rupture releasing huge amounts of freshwater into the Atlantic. This in turn was thought to have shut down ocean currents moving warm tropical water, resulting in colder conditions.
Scientists analysed spherules, droplets of solidified molten rock, deposited in Pennsylvania and New Jersey at the start of the Younger Dryas period. They identified geochemical "fingerprints" exactly matching the profiles of rock found in southern Quebec.
Although no "smoking gun" crater had been found, this was a strong clue that the spherules had been created by the massive temperatures and pressures of a meteor impact in Canada.
The findings appear in the journal Proceedings of the National Academy of Sciences.
"The Younger Dryas cooling impacted human history in a profound manner," said Professor Mukul Sharma, one of the study authors from Dartmouth College in New Hampshire, US.
"Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture."
