Humans set foot on the North American landscape thousands of years earlier than previously thought, according to new research that confirms the age of fossilized footprints from White Sands National Park in New Mexico using two additional dating methods.
The footprints date to between 21,000 and 23,000 years old, according to radiocarbon and optically stimulated luminescence dating techniques, researchers said Thursday, proving that our species, Homo sapiens, was already settled in North America during the most inhospitable conditions of the last Ice Age.
Extensive ice sheets covered wide swaths of the continent – reaching as far south as Illinois – in the midst of widespread glaciation.
A 2021 study by these researchers placed the footprints between 21,000 and 23,000 years old from small plant seeds embedded in the sediment. This was met with skepticism from some scientists who questioned the dating conclusion.
“Each dating technique has strengths and weaknesses, but when three different techniques converge on the same age range, the resulting ages are exceptionally robust,” said Jeff Pigati, a research geologist with the U.S. Geological Survey (USGS) in Denver and co-author of the research published in the journal Science.
“Our original results were controversial, and we knew from the beginning that we needed to independently assess seed ages to develop community confidence in them. This paper is that corroborating exercise,” added study co-lead author Kathleen Springer, also a research geologist at the USGS in Denver.
Homo sapiens emerged in Africa more than 300,000 years ago and subsequently spread around the world. Scientists believe that our species entered North America from Asia by crossing a land bridge that linked Siberia to Alaska.
According to Matthew Bennett, co-author of the study and Professor of Environmental and Geographical Sciences at Bournemouth University in England, previous archaeological evidence suggested that human occupation of North America began about 16,000 years ago.
“Indigenous peoples were there earlier than previously thought, before the great ice barrier at the height of the last glacial maximum closed the path south from Alaska. By what route and how they got there is yet to be determined.” For now, White Sands is just a dot on the map,” Bennett said.
The 2021 study dated the footprints using radiocarbon dating to determine the age of the seeds of a common aquatic plant called spiral ditch weed found next to the fossilized footprints.
This time, the researchers used radiocarbon dating of conifer pollen, thus avoiding any concerns about aquatic plants. They isolated thousands of conifer pollen grains from the same sediment layers as the stilt grass seeds. The age of the pollen statistically matched that of the seeds.