Roughly 13,000 years ago, a comet struck the Earth, wreaking havoc, extinction and climate change across the planet. It may also have nudged human populations on a path to civilisation as we know it today.
A new review supports a 2007 hypothesis for the so-called Younger Dryas impact, possibly the most devastating cosmic collision since the asteroid that wiped out the dinosaurs.
Dr Martin Sweatman at the University of Edinburgh sifted through more than a decade of hotly-debated papers and evidence before concluding that theory should be accepted. In particular, he points to a layer of geological data found at more than 50 archaeological sites spread across four continents – but particularly in North America and Greeland, where the largest fragments of the comet are believed to have hit.
Chemical signatures include an excess level of platinum, evidence of materials melted at extremely high temperatures and the detection of nanodiamonds, which are known to exist inside comets and form during high-energy explosions.
There's also tantalising clues at the relics found at some of the archaeological sites, Sweatman said.
"This major cosmic catastrophe seems to have been memorialised on the giant stone pillars of Göbekli Tepe, possibly the 'world's first temple', which is linked with the origin of civilisation in the Fertile Crescent of southwest Asia," he said. "Did civilisation, therefore, begin with a bang?"
Read more about comet impacts:
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- How planetary collisions happen
- 5 things you didn't know about comets and asteroids
The Younger Dryas impact theory states that a large comet, more than 4km across, collided with the Earth just before the start of the Neolithic period. It's thought to have disintegrated as it fell with multiple airbursts and impacts spread across the planet.
The effects would have been cataclysmic. Wildfires would have raged across entire continents, followed by a cold period known as an impact winter, caused by dust, ash and other material being thrown up into the atmosphere, deflecting solar radiation. It's also believed to have caused an abrupt mini ice age that lasted 1,000 years.
The impact likely contributed to the extinction of late Pleistocene megafauna, including mammoths, cave bears, and woolly rhinoceros. Humans, however, survived. But Sweatman and others believe the event left our species irrevocably changed.
The comet's impact coincides with major shifts in how and where human populations lived. It was then, in the so-called Fertile Crescent of southwest Asia (which spans parts of modern-day countries such as Egypt, Iraq and Lebanon), that humans adapted from hunter-gatherer lifestyles to ones centred on agriculture. They also lived a less nomadic lifestyle, creating permanent settlements for the first time.
Although the Younger Dryas impact theory has been questioned and debated, Sweatman argues that it should now be considered a consensus theory and calls for further research on its far-reaching consequences.
Older theories – including one by Isaac Newton – have suggested that events like this could have survived in our collective memory by inspiring tales of devastating floods, which appear in a number of religions. Some have even linked comet strikes to the myth of Atlantis.
