Researchers suggest an event that took place in Canada about 12,900 years ago is the reasons for the Earth's "dramatic climate shift," according to a new study by Dartmouth College.
The event reportedly occurred during the beginning of the Younger Dryas period, creating a colder, dryer global climate. The findings were published in the Proceedings of the National Academy of Sciences.
"The Younger Dryas cooling is a very intriguing event that impacted human history in a profound manner," said Mukul Sharma, a professor in the Department of Earth Sciences and one of the authors of a new paper. "Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture."
According to Dartmouth, big animals like mastodons, camels, giant ground sloths and saber-toothed cats disappeared in North America because of the extreme changes. The stress of a new environment caused the animals' human hunters, also known as Clovis people, to become hunter-gatherers, adding roots, berries, and smaller game to their diet.
Dartmouth researchers in the study did not argue that climate change had powerful effects on animal species roaming on Earth, but rather focused on the comet or meteor strike that may have caused the changes.
"The classical view of the Younger Dryas cooling interlude has been that a surge of meltwater from the North American ice sheet was behind it all," Dartmouth said. "According to this theory, a large quantity of fresh water accumulated behind an ice dam. The dam suddenly ruptured and dumped all this water into the Atlantic Ocean. The sudden influx is thought to have shut down the ocean currents that move tropical water northward, resulting in the cold, dry climate of the Younger Dryas."
Researchers working on the study reportedly discovered "conclusive evidence" which links a comet impact with the environmental changes, detailing a scenario in which the space matter collided with Earth.
"The report focuses on spherules, droplets of solidified molten rock expelled by the impact," Darmouth explained. "The spherules in question were recovered from Younger Dryas boundary layers at sites in Pennsylvania and New Jersey, the layers having been deposited at the beginning of the period. The geochemistry and mineralogy profiles of the spherules are identical to rock found in southern Quebec, where Sharma and his colleagues say the impact took place."
"What is exciting in our paper is that we have for the first time narrowed down the region where a Younger Dryas impact did take place," said Sharma, "even though we have not yet found its crater."
