David Bustos, White Sands' resource program manager, spent close to two decades noticing footprint-shaped dark patches on the Alkali Flat playa before anyone dug into what they actually were. Excavations began in 2009. By the time the findings reached Science magazine in September 2021, researchers had traced a nearly mile-long trackway of a person carrying a small child on one hip, setting them down, and picking them back up, over and over, across ground that has been dry for millennia.
The dates attached to that trackway, and to dozens like it nearby, would put people in North America roughly ten thousand years earlier than the standard timeline most Americans learned in school. That claim didn't go unchallenged. It also didn't fall apart.
Years of Looking Before Anyone Dug
Bustos first spotted the ghost tracks, footprint-shaped dark spots visible only under specific soil-moisture conditions, well before formal excavation started in 2009. What followed was a genuinely large, multi-institution effort: Matthew Bennett of Bournemouth University and Bustos led the work, in partnership with the U.S. Geological Survey's Jeffrey Pigati and Kathleen Springer on the dating, along with researchers from the University of Arizona and Cornell, done in consultation with Native American tribal partners. The findings reached the public in September 2021, in the journal Science.
What the Mud Actually Preserved
That mile-long caregiver trackway is the most vivid of them: shifting stride patterns and occasional signs of slipping under extra weight show a person carrying a young child on one hip for a stretch, then setting the child down, over and over, moving at a pace researchers calculated around five and a half feet per second through slick mud, notably fast. She made the trip alone in one direction and returned without the child. A mammoth's tracks cross straight through the path, seemingly unbothered by the human traffic.
A separate trackway preserves something closer to a hunt: a human footprint sits directly inside a Harlan's ground sloth's own track, matching its stride for more than ten paces, with a second set of prints approaching from the side on tiptoe. The sloth's tracks show it reared up at one point, a defensive posture. What happened next isn't preserved. Elsewhere in the same layers, researchers have documented far less dramatic, equally human traces: children's prints showing what looks like jumping, skipping, and sloshing around in the mud, ordinary play, fossilized by accident.
Plan Your White Sands Visit
Alkali Flat Trail traces the edge of the same ancient lakebed where these trackways were found. The trip planner can help you build a day around it.
Open the Trip PlannerThe Dates Got Challenged, Then Confirmed Three Different Ways
The original dates came from radiocarbon testing of Ruppia cirrhosa seeds, ditch grass, found in layers directly above and below the trackways: roughly twenty-one thousand to twenty-three thousand years old. Researchers including Loren Davis of Oregon State University raised a real methodological concern, that aquatic seeds can draw carbon from lake water rather than the atmosphere, potentially skewing the dates older than the true age.
- Original method SEED RADIOCARBON, 2021
- Confirmation round one POLLEN + LUMINESCENCE, 2023
- Confirmation round two MUD RADIOCARBON, 2025
- Total consistent dates 55, ACROSS MULTIPLE LABS
In October 2023, USGS-led researchers answered that objection with two independent methods on the same stratigraphy: radiocarbon dating of land-based conifer pollen, which sidesteps the lake-water problem entirely, and optically stimulated luminescence dating of quartz sand grains, an unrelated physical technique measuring time since the grains last saw sunlight. Both landed in the same twenty-one-thousand-to-twenty-three-thousand-year window as the original seeds. In June 2025, a third team dated the mud itself, again independently, again converging on the same range, bringing the total to fifty-five consistent radiocarbon dates across multiple labs and three distinct material types. Some skepticism about exact stratigraphic placement has continued in the literature since, but the broad scientific consensus has moved firmly toward accepting the older date.
Protected, Not Displayed
The excavation sites sit in backcountry terrain on the Alkali Flat playa and aren't open for public viewing, protected as active research ground rather than developed as a trail feature. What the park does offer, since a January 2024 exhibit opened at the visitor center, is cast replicas of the human footprints, along with at least one authentic fossilized print displayed under glass. If a find this significant makes you want to stand where it happened, the honest answer is that you mostly can't, not yet, and maybe not ever.
Facts and figures checked against the National Park Service's own fossilized footprints page, USGS's discovery announcement and 2023 independent-age-estimate publication, and the original and follow-up Science papers. The 2025 mud-dating study checked against USGS/university coverage of that publication. The scientific consensus is described here as broad rather than unanimous, since some methodological critique has continued in the literature even after the 2023 and 2025 confirmations; readers wanting the full technical debate should consult the cited Science papers directly.
Somewhere out on Alkali Flat, under ground that hasn't held water in thousands of years, a woman's hip ached from carrying a child she eventually set down and walked away from alone. Fifty-five dates from three independent methods now agree on roughly when that happened, more than twenty thousand years ago, long before anyone thought people were here at all. The mud kept the record. It just took two decades of looking, and four more years of arguing about it, to read it correctly.