The ice age is well-known for the “megafauna,” or giant mammals, that walked the Earth. In a time when much of the planet was frozen, the majestic wooly mammoth ran the show. Something caused the mammoths and other giant mammals to go extinct, and according to a report from CS Monitor, scientists think they have figured out what it was.

During the unstable climate of the late Pleistocene era, which lasted from 60,000 to 12,000 years ago, the planet was struck by sudden climate shifts called interstadials. During these peaks and troughs, the temperature on Earth rose from 7 to 29 degrees Fahrenheit over just a few decades.

Large animals, like short-faced bear, cave lions, and the wooly mammoth likely had a hard time adapting to the increased temperatures and died off due to the heat. Even if they were able to withstand the temperature jump, many of the plants and animals they consumed as prey probably were not.

Interstadials are known to alter global precipitation and vegetation patterns as well. Temperature drops in the late Pleistocene weren’t linked to any animal die-offs in the fossil record; only upward interstadial periods and high temperatures were connected to large-scale extinctions.

Ancient humans were also probably responsible for the extinction of wooly mammoths and other megafauna, by disturbing their environment and hunting them down to dangerously low levels.

Researchers analyzed DNA from dozens of megafauna species from the late Pleistocene, where they paired large die-offs with historical climate data extracted from the ice of a Greenland glacier.

By comparing the fossil and climate records, scientists were able to accurately link periodic changes in the climate with the mass-extinction of these giant mammal species.