Ancient footprints could be oldest traces of humans in the Americas White Sands National Park, in southern New Mexico, is known for chalk-coloured dunes that stretch for hundreds of square kilometres. But at the height of the last Ice Age, the region was wetter and grassier. Mammoths, giant sloths and other animals walked the muddy shores of shallow lakes that grew and shrank with the seasons. And they had company.

In a landmark study published on 23 September in Science1, researchers suggest that human footprints from an ancient lakeshore in the park date to between 21,000 and 23,000 years old. If the dating is accurate — which specialists say is likely — the prints represent the earliest unequivocal evidence of human occupation anywhere in the Americas. (read on)