Comet impact may have kick-started agriculture on Earth, scientists say

A comet that struck the Earth more than 12,000 years ago cooled the climate, leading hunter-gatherers to try something new

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In the movie 2001: A Space Odyssey, a visitor arrives from outer space in humanity’s distant past, forever changing the destiny of our species. Now scientists suspect something similar may have happened in real life.

No, it wasn’t an alien monolith that landed on Earth and made us smarter. But it did come from space. Some 12,800 years ago, the debris trail of a disintegrating comet entered the Earth’s atmosphere, resulting in more than 50 airbursts and ground impacts across the globe.

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The shockwaves, explosions and fires caused extensive damage. But it was the subsequent climate change that really did a number on things. Large mammals such as the mammoth, the saber-toothed cat and the American camel were driven to extinction. And in the smouldering remains of the prehistoric settlement of Abu Hureyra, in modern-day Syria, the surviving humans realized they could no longer survive on a hunter-gatherer lifestyle.

They would need to try something else. Agriculture.

Scientists have long known that humans started turning to agriculture about 12,000 years ago, first in the Middle East, and later in other parts of the world. Now a quartet of related research papers, all appearing in the journal Science Open, makes the case that it was global cooling caused by the cometary impact that forced humans to change their ways.

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“In this general region (of Abu Hureyra) there was a change from more humid conditions that were forested and with diverse sources of food for hunter-gatherers, to drier, cooler conditions when they could no longer subsist only as hunter-gatherers,” said Earth scientist James Kennett, one of the papers’ authors and a professor emeritus at the University of California Santa Barbara, in a press release from the university.

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“The villagers started to cultivate barley, wheat and legumes,” he noted. “This is what the evidence clearly shows.”

Abu Hureyra was already famous among archaeologists for its evidence of the earliest known transition from foraging to farming. Buried layers of organic remains show that, in the centuries before the impact, the people’s diet consisted of wild legumes, wild grains and wild fruits and berries.

But by a thousand years after the impact, fruits and berries disappear, replaced by what are known as Neolithic “founder crops” — emmer wheat, einkorn wheat, hulled barley, rye, peas, lentils, bitter vetch, chickpeas and flax. At the same time, the spread of drought-resistant plants point to a cooler, drier climate.

Meanwhile, the archeological record not only shows a significant drop the in the region’s population — what you’d expect from a cosmic cataclysm — but evidence of livestock pens and other signs of animal domestication.

And at the boundary between hunter-gatherers and farmers, a “black mat” with high concentrations of platinum, nano-diamonds and tiny metallic spherules. All these suggest temperatures and pressures that would have been unachievable at that time from anything other than a massive natural explosion.

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The comet-impact hypothesis has a problem in that there are no craters associated with the impacts of multiple comet fragments. But the scientists were able to compare shock-fractured quartz from the time period with similar finds at the sites of nuclear tests from the 1940s and ‘50s. Those airburst events could produce the same types of quartz grains without creating a large or long-lasting crater. Similarly, the comet fragments could have done massive damage just by exploding in the air.

Taken together, says Kennett, the new research “implies a novel causative link among extraterrestrial impacts, hemispheric environmental and climatic change, and transformative shifts in human societies and culture, including agricultural development.” Farming may have been, in a strange way, a gift from the stars.

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