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Frozen DNA evidence trapped in soil suggests that mammoth and wild horse populations petered out slowly, instead of vanishing quickly. Leonello Calvetti via Getty Images
Smithsonian Magazine has a story about research that shows that woolly mammoths and other Ice Age animals survived up to about 5,000 years ago instead of the accepted 13,000 years. Frozen permafrost samples collected about 10 years ago were analyzed and they revealed DNA of wooly mammoths, wild horses, and steppe bison. The research was published in the journal Nature Communications.
Most DNA samples are taken from materials like bone or hair, but soils also contain also genetic residue that animals leave behind as they move through an environment, according to Gizmodo’s Isaac Schultz. The soil samples sat in a freezer untested for years until Tyler Murchie, an archaeologist specializing in ancient DNA at McMaster University, decided to reinvestigate them.
“I found them in the freezers while looking for a new project during my PhD,” Murchie, lead author of the new paper, tells Gizmodo. “One of my responsibilities at the ancient DNA center is freezer maintenance, so I had a good idea of what cool stuff might be in there waiting for someone to study.”
The research team was eager to understand how and why large North American species like mammoths and bison survived for thousands of years before they vanished. During the Pleistocene-Holocene transition roughly 11,000 to 14,000 years ago, the climate went through rapid changes that led to the extinction of many Ice Age species like mastodons and saber-toothed cats. Based on previous research, scientists suspected two factors were driving extinctions: a loss of food due to a warming climate or overhunting by humans. It’s a question scientists have "been grappling with for some 270 years,” says Murchie to Gizmodo. In the new paper, Murchie's team presents a DNA record of the plant and animal community dating back 30,000 years.
