Some of the first people in North America lived through extreme climate change at the peak of the last ice age, a new study suggests.

Researchers studied ancient pollen locked in rocks at White Sands National Park in New Mexico, which houses an archaeological site thought to contain the oldest human footprints in the Americas. The researchers previously dated those footprints to around 21,000 to 23,000 years ago, though their age is the subject of some scientific debate because they are significantly older than other Indigenous sites in the Americas.