New Mexico Footprints are Oldest Sign of Humans in Americas
Fossil footprints date back to between 21,000 and 23,000 years ago, upending previous theory that humans reached continent later.
New research confirms that fossil human footprints in New Mexico are probably the oldest direct evidence of human presence in the Americas, a finding that upends what many archaeologists thought they knew.
The footprints were discovered at the edge of an ancient lakebed in White Sands national park and date back to between 21,000 and 23,000 years ago, according to research published on Thursday in the journal Science.
The estimated age of the footprints was first reported in Science in 2021, but some researchers raised concerns about the dates. Questions focused on whether seeds of aquatic plants used for the original dating may have absorbed ancient carbon from the lake ā which could, in theory, throw off radiocarbon dating by thousands of years.
The new study presents two additional lines of evidence for the older date range. It uses two entirely different materials found at the site, ancient conifer pollen and quartz grains.
The reported age of the footprints challenges the once conventional wisdom that humans did not reach the Americas until a few thousand years before rising sea levels covered the Bering land bridge between Russia and Alaska, perhaps about 15,000 years ago.
āThis is a subject thatās always been controversial because itās so significant ā itās about how we understand the last chapter of the peopling of the world,ā said Thomas Urban, an archaeological scientist at Cornell University, who was involved in the 2021 study but not the new one.
Thomas Stafford, an independent archaeological geologist in Albuquerque, New Mexico, who was not involved in the study, said he āwas a bit skeptical beforeā but now is convinced.
The new study isolated about 75,000 grains of pure pollen from the same sedimentary layer that contained the footprints.
āDating pollen is arduous and nail-biting,ā said Kathleen Springer, a research geologist at the US Geological Survey and a co-author of the new paper.
Ancient footprints of any kind can provide archaeologists with a snapshot of a moment in time. While other archeological sites in the Americas point to similar date ranges ā including pendants carved from giant ground sloth remains in Brazil ā scientists still question whether such materials really indicate human presence.
āWhite Sands is unique because thereās no question these footprints were left by people, itās not ambiguous,ā said Jennifer Raff, an anthropological geneticist at the University of Kansas, who was not involved in the study.
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