The 2009 discovery of footprints (human and animal) left behind in layers of clay and silt at New Mexico’s White Sands National Park sparked a contentious debate about when, exactly, human cultures first developed in North America. Until about a decade ago, it seemed as if the first Americans arrived near the end of the last Ice Age and were part of the Clovis culture, named for the distinctive projectile points they left behind near what’s now Clovis, New Mexico. But various dating methods indicated the White Sands footprints are 10,000 years older. Now there is a fresh independent analysis that agrees with those earlier findings, according to a new paper published in the journal Science Advances.

As previously reported, earlier archaeological evidence had suggested the Clovis people made their way southward through a corridor that opened up in the middle of the ice sheets between 13,000 and 16,000 years ago. Subsequent archaeological evidence—such as a 14,500-year-old site in Florida and stone tools dating to 16,000 years ago in western Idaho—suggested that the Clovis people were actually not the first to arrive. It also made it look much more likely that the first Americans had skirted the edge of the ice sheets along the Pacific Coast.

The White Sands footprints further muddled the narrative. In 2019, Bournemouth University archaeologist Matthew Bennett and his colleagues excavated the White Sands area and found a total of 61 human footprints east of an area called Alkali Flat, which was once the bed and shoreline of an ancient lake. Over time, as the lake’s edge expanded and contracted with shifts in climate, it left behind distinct layers of clay, silt, and sand. Seven of those layers, in the area Bennett and his colleagues excavated, held human tracks along with those of long-lost megafauna.