Last update: October 16, 2025

White Sands Footprints: America's First Steps

Fossilized human footprints in the sediments of White Sands, New Mexico

Traces 23,000 Years Old

In 2021, a team from the USGS revealed a major discovery: perfectly preserved human footprints in the gypsum of the White Sands basin, New Mexico. These tracks, dated using radiocarbon (14C) dating, go back about 23,000 years, predating the traditionally accepted human colonization of the Americas (around 13,000 years for the Clovis culture) by several millennia.
These footprints likely belonged to adolescents and children moving along an ancient lakeshore during a cold and humid climate at the Last Glacial Maximum.

N.B.:
The carbon-14 method is based on the radioactive decay of the isotope \(^{14}\mathrm{C}\), present in organic tissues as long as they exchange carbon with the atmosphere.
Upon the organism's death, this exchange stops, and the decay of \(^{14}\mathrm{C}\) follows an exponential law with a half-life \(T_{1/2} = 5730 \pm 40\) years.
By measuring the remaining \(\frac{^{14}\mathrm{C}}{^{12}\mathrm{C}}\) ratio in a sample, its age can be estimated up to about 50,000 years.
This technique, developed by Willard Frank Libby (1908-1980), is based on the general principle of decay kinetics and requires corrections for variations in atmospheric \(^{14}\mathrm{C}\) levels over time.

A Unique Geological and Paleoenvironmental Context

White Sands National Monument: Southern New Mexico (USA)

The White Sands site is located in a vast evaporation plain formed by the drying of Lake Otero. The white sediment, rich in gypsum, has allowed the exceptional preservation of footprints. These are imprinted in alternating layers of mud and volcanic ash.
Recrystallized gypsum formed a natural mold preventing erosion. Thanks to fine stratigraphy and the dating of ruppia seeds found in the same layers, researchers were able to estimate the precise chronology of these human movements.

N.B.;
In the United States, the term "National Monument" designates a territory protected by presidential proclamation under the Antiquities Act of 1906.

Major Implications for the Colonization of the Continent

Before this discovery, the dominant theory held that the first humans in America crossed the Bering Strait after the melting of the glaciers, around 13,000 years before our era. The White Sands footprints challenge this timeline.
They suggest a human presence at least 10,000 years earlier, implying arrival by coastal route or pre-glacial migration.
This hypothesis aligns with the work of Ruth Gruhn (1921-2021), an anthropologist who long argued for an earlier coastal settlement of the Americas.

Physical Analysis of the Footprints

Metric and morphological analysis of the footprints reveals lengths between 20 and 24 cm, indicating individuals of average height, likely aged 10 to 15 years.
Researchers modeled the pressure exerted on the substrate from the depth of penetration: \[ P = \frac{F}{S} \] where \(F\) is the force exerted by body weight and \(S\) is the contact area of the foot.
Variations in \(P\) indicate walking speeds of about 1.7 m/s, typical of a brisk walk. These data are compared to animal tracks (giant sloths, mammoths) also present, revealing direct interactions between humans and megafauna.

A Chronological and Cultural Revolution

The White Sands footprints provide direct, not just archaeological, evidence of human presence during the Late Pleistocene. They are part of a growing body of evidence: lithic tools from Chiquihuite (Mexico), bones from Bluefish Caves (Canada), or traces of ancient hearths in Chile (Monte Verde).
This convergence suggests that modern humans reached America long before the end of the last ice age and coexisted with megafauna until their gradual extinction around 10,000 years ago.

N.B.:
The Late Pleistocene corresponds to the final part of the Pleistocene, extending approximately from 126,000 to 11,700 years before our era.
This period is characterized by significant climatic fluctuations, including the Last Glacial Maximum (~26,500 to 19,000 years BP), which led to the expansion of continental glaciers, a drop in sea levels, and changes in terrestrial and marine ecosystems.
The Late Pleistocene is also crucial for the study of modern human evolution and the colonization of continents, as it coincides with the appearance and dispersal of Homo sapiens populations out of Africa and coexistence with now-extinct megafauna.

Table of Paleontological and Archaeological Sites of the American Pleistocene

Paleontological and Archaeological Sites of the American Pleistocene
Site	Location	Estimated Dating	Comment
White Sands	New Mexico, USA	~23,000 years BP	Fossilized human footprints; direct evidence of pre-Clovis presence
Bluefish Caves	Yukon, Canada	~24,000 years BP	Human-worked bones; habitat during the Last Glacial Maximum
Monte Verde	Chile	~14,500 years BP	Remains of human campsites; first evidence of South American settlement
Cueva de Chiquihuite	Mexico	~26,000 years BP	Lithic tools not associated with direct fossil remains
Meadowcroft Rockshelter	Pennsylvania, USA	~16,000 years BP	Pre-Clovis tools; evidence of earlier human occupation than expected
Page-Ladson	Florida, USA	~14,500 years BP	Footprints and lithic tools in freshwater; fluvial context
Paisley Caves	Oregon, USA	~14,000 years BP	Human remains and artifacts; evidence of seed consumption
Lehner Ranch	Arizona, USA	~12,000 years BP	Clovis site; remains of hunted megafauna
Folsom	New Mexico, USA	~10,800 years BP	Folsom culture; evidence of hunting weapons and megafauna
Calico	California, USA	~200,000-130,000 years BP	Controversial artifacts; supposed ancient human occupation
Cooper’s Ferry	Idaho, USA	~16,000 years BP	Pre-Clovis; lithic tools and hearth remains
Manis Mastodon	Washington, USA	~14,000 years BP	Mastodon bone pierced by a wooden spear; human-megafauna coexistence
Cerutti Mastodon	California, USA	~130,000 years BP	Fractured mastodon bones; controversial human occupation

Source: United States Geological Survey (USGS), Smithsonian Magazine, Nature, 2020.