WASHINGTON – Fossil footprints discovered in New Mexico indicate that early humans roamed North America about 23,000 years ago, researchers reported Thursday.
The first footprints were found in 2009 in a dry lake bed in White Sands National Park. Scientists from the US Geological Survey recently analyzed seeds trapped in the footprints to determine their estimated age of about 22,800 and 21,130 years ago. The findings may shed light on a mystery that has long puzzled scientists: When did people first arrive in the Americas after dispersing from Africa and Asia?
Most scientists believe that the ancient migration came via the now-submerged land bridge that connected Asia with Alaska. Based on various evidence – including stone tools, fossil bones and genetic analysis – other researchers have offered a range of possible dates for human arrival in the Americas, between 13,000 and 26,000 years ago or more.
The current study provides a more solid baseline of when humans were definitely in North America, although they may have arrived earlier, the authors say. Fossil footprints are more indisputable and direct evidence than “cultural artifacts, modified bones, or other traditional fossils,” they wrote in the journal Science, which published the study Thursday.
“What we present here is proof of a firm time and place,” he said.
Based on the size of the footprints, researchers believe that at least some were made by children and teenagers who lived during the last ice age.
David Bustos, the park’s resource program manager, saw the first footprints in the pristine wetland in 2009. He and others found more in the park over the years.
“We knew they were out of date, but we had no way of dating the print before we discovered some (seeds),” he said on Thursday.
Made of fine silt and clay, footprints are delicate, so researchers had to act quickly to collect samples, Bustos said.
“The only way to save them is to record them – to take lots of pictures and make 3D models,” he said.
Earlier excavations in White Sands National Park have uncovered fossil tracks left by a saber-toothed cat, dire wolf, Colombian mammoth and other ice age animals.