The footprints, the earliest firm evidence for humans in the Americas, show that people must have arrived here before the last Ice Age.
A new discovery offers definitive evidence that humans were in North America far earlier than archaeologists previously thought — a whopping 7,000 years earlier.
Fossil footprints found on the shore of an ancient lake bed in New Mexico's White Sands National Park date as far back as 23,000 years ago, making them the oldest ever found in North America. That timing means humans occupied southern parts of the continent during the peak of the final ice age, which upends our previous understanding of when and how they moved south.
The previous idea was that the first people to occupy North America crossed a land bridge that existed between modern-day Siberia and Alaska during the last ice age, between 26,500 and 19,000 ago. According to that theory, they would have had to settle near the Arctic because ice sheets covering Canada made it impossible for them to go south. Then later, once these glaciers melted between 16,000 and 13,500 years ago, the migration toward South America began.
This new finding, however, "definitively places humans in North America at time when the ice sheet curtains were very firmly closed," Sally Reynolds, a paleoecologist at Bournemouth University in England and co-author of the new study.
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