In the scrubby expanse of White Sands National Park in New Mexico, a set of impressions pressed into ancient mud has continued to unsettle assumptions about when people first moved through the Americas. The markings, preserved in layers of sediment that later hardened into gypsum, were first described in a 2021 study published in Science, titled ‘Human footprints near ice age lake suggest surprisingly early arrival in the Americas’, which revealed that they placed them far earlier than the long-accepted timeline.