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White Sands footprints (New Mexico)
c. 23,000–21,000 years ago (debated)· Fossil or site· Human ancestors & us
DebatedScientists disagree about when, how or why.
Human footprints on an ancient lakebed in New Mexico that may be 23,000–21,000 years old, if the disputed dates hold.
See it on the Life map →What happened
On the dry bed of ancient Lake Otero, in White Sands National Park, hundreds of human footprints, many left by children and teenagers, lie in layers alongside tracks of mammoths and giant ground sloths. They show up only when ground moisture is just right, hence the nickname 'ghost tracks'. In 2021 a team led by Matthew Bennett and park scientist David Bustos dated the layers using seeds of a water plant, ditch grass, buried above and below the prints.
Why it matters
If the dates hold, people were in North America at the peak of the last ice age, thousands of years before most other evidence, rewriting the timeline for the Americas.
The evidence (fossils, genes, rocks)
Radiocarbon dates on ditch-grass seeds (2021), backed in 2023 by dates on conifer pollen and by luminescence dating of quartz grains, which measures when sand was last exposed to sunlight.
Still debated
Some archaeologists still question the dates, and no stone tools or campsites have been found with the prints. Who these people were, and whether they left descendants, is unknown.
Connections (2)
▸White Sands footprints (New Mexico) may push back the date of Peopling of the AmericasDebated
The connection
Most well-dated sites placed the first Americans at about 16,000–14,000 years ago. If White Sands' footprints are 23,000–21,000 years old, people were already in what is now New Mexico, south of the ice sheets, about 7,000 years earlier. That would mean they arrived before the ice-age peak blocked the inland route.
When and how
White Sands National Park, New Mexico; published in Science in 2021 by Matthew Bennett, David Bustos, Jeffrey Pigati, Kathleen Springer and colleagues; follow-up dating in 2023.
How sure are we?
Three dating methods (seeds, pollen and quartz luminescence) agree on about 23,000–21,000 years, and the footprints are clearly human.
Debates and open questions
Critics ask whether the seeds and pollen were washed in from older layers or skewed by old carbon in the water; no tools have been found; how people got there is unknown.
▸White Sands footprints (New Mexico) date to the coldest phase of Pleistocene ice agesDebated
The connection
If their dates hold, the footprints fall within the Last Glacial Maximum, about 26,000–19,000 years ago, when ice sheets reached their largest extent. Ancient Lake Otero then filled the basin, and its muddy shores recorded people walking alongside mammoths and giant ground sloths. The tracks show the region was wetter and grassier than today's desert.
When and how
Tularosa Basin, New Mexico, during the last ice-age peak; human, mammoth and ground-sloth tracks lie in the same lakeshore layers.
How sure are we?
Layer-by-layer dating of the lakebed, plus pollen showing ice-age conifers nearby, places the tracks in the coldest phase of the last glacial period.
Debates and open questions
How people coped and traveled at the height of the cold, and whether they came before ice closed the north or along the coast.