Expanded excavations at White Sands National Park in New Mexico place people on the shores of Ice Age Lake Otero between 23,500 and 21,700 years ago, during the Last Glacial Maximum. The same sediment layers preserve rapid swings from a perennial lake to an arid playa, allowing scientists to match unmistakable human activity with environmental change at roughly a human-generation timescale.
How old are the White Sands footprints?
The U.S. Geological Survey’s refined chronology dates the footprint-bearing sequence to 23.5–21.7 thousand years ago (ka). Excavations have identified 20 stratigraphic horizons containing in-situ human footprints, tracks made by Ice Age megafauna and linear features interpreted as travois lines.
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Independent age controls include radiocarbon dates from conifer pollen and aquatic seeds. National Park Service documentation lists calibrated ages of 22,860 ± 320 and 21,130 ± 250 years ago for Ruppia cirrhosa seeds found above and below footprint layers. The agreement among different materials and methods is important because it tests whether the tracks were formed at the same time as the dated sediments rather than being moved into younger or older deposits.
What the new excavations found
A long sequence of people and animals
The tracks are preserved along the former margin of Lake Otero. Human paths occur beside or across trackways made by mammoths, giant ground sloths, dire wolves and other Ice Age animals. Most excavated human prints appear to have been made by teenagers and children, based on stature and walking speed. One trackway records an adult carrying a toddler. In another, human prints occur within a giant-sloth trackway, documenting activity on the same surface rather than merely nearby finds.
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Travois lines add evidence of movement
Linear grooves associated with the footprint horizons are interpreted as travois features, consistent with people dragging loads across wet or soft lake-margin sediment. The lines extend the behavioral evidence beyond individual steps: the site records repeated travel and transport across a changing shoreline.
How scientists reconstructed the Ice Age environment
University of Arizona researchers reconstructed conditions at approximately 50-year, human-generation resolution, unusually fine for a terrestrial paleoclimate record in the southwestern United States. Samples were analyzed with several independent indicators:
- Pollen: new extraction procedures isolated as many as 75,000 grains per sample, allowing vegetation changes to be tracked in detail.
- Radiocarbon dating: conifer pollen and aquatic seeds supplied age controls through the footprint-bearing sequence.
- Sediment geochemistry and biomarkers: chemical changes helped identify shifts in water level, aridity and depositional conditions.
- Leaf-wax hydrogen isotopes: isotope values recorded changes in water availability, including swings occurring within a century.
- Stratigraphy: the order and position of lake, shoreline and playa deposits tied each proxy to the physical surfaces where people and animals walked.
Jessica Tierney, a University of Arizona professor of geosciences, said the sediments are unusual because they reveal fluctuations relevant to people at very high temporal resolution. Kathleen Springer, a USGS research geologist and co-lead author, described the expanded sampling as a long-standing goal: connecting the footprint site to the environmental conditions at the height of the Last Glacial Maximum.
What changed at Lake Otero?
From a colder, wetter lake to a playa
At the Last Glacial Maximum, the White Sands basin was cooler and wetter than it is today and held perennial Ice Age Lake Otero. Pollen and aquatic-plant evidence show the lake’s water level rose and fell for about 1,500 years before the basin contracted into a flat playa. People continued to cross the former shoreline for nearly two millennia, so the tracks span a landscape that was being transformed while it was still used.
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Vegetation reorganized
The surrounding plant community shifted from conifer forest toward sagebrush and oak steppe as the lake receded. That transition indicates more than a falling shoreline: it reflects a regional change in temperature, precipitation and effective moisture.
An abrupt aridification episode
USGS analyses identify a major increase in aridity that coincided with Dansgaard–Oeschger event 2, an abrupt climate shift recorded around 23.2 ka in Greenland ice cores. Leaf-wax isotopes indicate that local water availability could change substantially within a century. Tierney said the magnitude and timing of the White Sands aridity shifts show that local conditions followed global climate changes, while still producing a distinctive response in the basin.
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Why the footprints matter for the peopling of North America
Footprints are direct evidence that people stood and walked at a specific place, unlike artifacts whose original association with a dated layer can be debated. The White Sands sequence therefore links human presence directly to a securely dated Last Glacial Maximum landscape. It strengthens the case that people occupied North America thousands of years earlier than the once-common estimate of roughly 13,500–16,000 years ago.
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The site is especially valuable because human traces and climate indicators occur in the same stratigraphic sequence. Scientists can ask not only whether people were present, but what kind of shoreline, vegetation and water conditions they encountered. The record does not by itself identify every group’s route into the continent or explain how populations adapted; it establishes an early presence and the environmental context in which those people lived.
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Anthropologist Ed Jolie emphasized that the people represented by the tracks were ancestors of contemporary Indigenous peoples. He said the findings provide scientific evidence consistent with Indigenous oral traditions asserting presence “since time immemorial,” while reinforcing the sovereignty and deep history of Native nations.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the chronology and evidence show
| Evidence | Result | Why it matters |
|---|---|---|
| Footprint-bearing sequence | 23.5–21.7 ka | Places repeated human activity in the Last Glacial Maximum. |
| Ruppia cirrhosa seeds | 22,860 ±320 and 21,130 ±250 years ago | Provides dated aquatic material above and below footprints. |
| Stratigraphic horizons | 20 horizons | Shows that tracks formed during multiple episodes, not one isolated visit. |
| Environmental resolution | About 50 years | Approaches the timescale of a human generation. |
| Pollen recovery | Up to 75,000 grains per sample | Supports detailed reconstruction of changing plant communities. |
| Lake history | Perennial lake to playa over roughly 1,500 years of water-level fluctuations | Records the basin’s progressive aridification while people still used its margin. |
Can visitors see the original tracks?
The original excavated footprints are currently inaccessible to visitors. White Sands National Park directs the public to a visitor-center exhibit with cast footprints installed in January 2024. The casts provide a view of the track shapes without opening the fragile original surfaces to routine traffic.
The central takeaway
White Sands preserves a rare combination: unambiguous human footprints, animal trackways and a high-resolution environmental archive in the same layers. Between about 23,500 and 21,700 years ago, people—including children and an adult carrying a toddler—moved along a shoreline that shifted from a cool, wet lake environment toward an arid playa. The record shows that humans in North America experienced large climate changes within lifetimes during the last ice age, and it places their presence far earlier than the former 13,500–16,000-year benchmark.
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