Scientists have found evidence that a comet rained chunks onto Earth 12,000 years ago and set off fires that caused an ice age and animal extinctions. CC0 Creative Commons

Our prehistoric ancestors thought the Ice Age was over when chunks of a huge comet came crashing down onto Earth about 12,800 years ago and sparked massive fires, the effect of which plunged the planet into another cold period and drove many animals into extinction.

Scientists have previously envisioned this scenario and now new research has found evidence in its support. Two studies in the Journal of Geology describe samples taken from ice and from sediment that back up the impact-driven climate change, a cold period known as the Younger Dryas. According to the researchers, chemical analysis of the samples, formed in the time of the impact event and taken from dozens of sites all over the world, suggests enough fires broke out to cloud the sky and block out the sun, which would have led to the roughly thousand-year cold era.

“The hypothesis is that a large comet fragmented and the chunks impacted the Earth, causing this disaster,” researcher Adrian Melott said in a statement from the University of Kansas. “A number of different chemical signatures — carbon dioxide, nitrate, ammonia and others — all seem to indicate that an astonishing 10 percent of the Earth’s land surface, or about 10 million square kilometers, was consumed by fires.”

At the same time the previously warming planet was cooling off, plants would have been dying and ocean currents would have shifted.

After a millennia had passed and the planet started to warm up again, “people again emerged into a world with fewer large animals and a human culture in North America that left behind completely different kinds of spear points,” the university explained.

A lot of large North American mammals mysteriously went extinct together about 11,000 years ago, including saber-toothed cats, woolly mammoths, giant ground sloths and mastodons. The scenario the scientists describe could offer an explanation for their disappearances.

According to the researchers, the comet that broke into the pieces that rained down on Earth would have originally been about 62 miles across and what remains of it is still flying around the solar system.

“Computations suggest that the impact would have depleted the ozone layer, causing increases in skin cancer and other negative health effects,” Melott said. “The impact hypothesis is still a hypothesis, but this study provides a massive amount of evidence, which we argue can only be all explained by a major cosmic impact.”