People really were walking around in the southwestern US during the middle of the last Ice Age, according to a recent study that double-checked the dates on a set of surprisingly ancient human footprints at White Sands National Park.

Many thousands of years ago, someone walked along the muddy shore of an ancient lake at what’s now White Sands. They crushed ditchgrass seeds and grains of conifer pollen beneath their feet with every squishing, slippery step. Bournemouth University archaeologist Matthew Bennett and his colleagues (including the authors of the current study) unearthed eight layers of tracks at the site in early 2020; they radiocarbon-dated the ditchgrass seeds from the oldest layer of footprints to 23,000 years old and the youngest layer to around 21,000 years old.