So what caused the mass extinction of large animals in Europe and North America like the woolly mammoth, Irish elk, and European elephant back during the last Ice Age? Some say the arrival of humans finished them off, some say it was all that ice — but a new study indicates that climate cycles were likely more to blame than us.

University of Adelaide scientist Alan Cooper and a team of researchers published a study in the journal Science that tried to settle the “overkill versus climate” debate on what caused these animals to die out, according to a Forbes.com report.

The study uses fossils that were aged with radiocarbon dating, and also used ancient DNA. Usually, such fossils can only be used to differentiate between species, but since these are only thousands of years old rather than millions of years old, DNA can be extracted and scientists can figure out if two similar fossils are actually the same species — many times, they found this is not the case. That means, many times what scientists thought was a continuous record of one species was actually just a lot of bones from different species.

The “overkill” argument had been bolstered in the past by the lack of extinction events during glacial periods, but scientists were able to find these extinction events by finding species turnover in the ancient DNA.

Scientists thought that extinctions would happen during the cooling parts of climate cycles in the last glacial period, which spans from 110,000 to just 11,650 years ago. However, scientists found that it was actually the warming periods following the Last Glacial Maximum — called Dansgaard-Oescheger events — that resulted in extinctions.

These events happened about 25 times during the last glacial period and usually feature climate oscillations, mostly in the Northern Hemisphere. This includes periods of rapid warming that takes place in just decades, followed by a cooling period that is gradual.

This warming phase in D-O events appears to be closely tied with the extinctions.