Humans may have been in the Americas much earlier than once thought, fossil research shows

Scientists have uncovered new evidence showing that humans in the Americas may have existed several thousands of years earlier than once thought, according to a report published Thursday in the academic journal Science. 

"This study illustrates the process of science — new evidence can shift long held paradigms," U.S. Geological Survey acting Rocky Mountain director Allison Shipp said in a statement Thursday.

Ancient fossilized footprints found in New Mexico's White Sands National Park displayed evidence suggesting that humans lived in North America during the Last Glacial Maximum, which dates back to around 21,000 to 23,000 years ago. Scientists have contested when the first humans lived in the Americas, with some finding evidence for life around 15,000 years ago, according to Smithsonian Magazine.

Researchers from White Sands National Park, the National Park Service, U.S. Geological Survey, the University of Arizona, Bournemouth University and Cornell University analyzed multiple footprint surfaces found buried between layers of gypsum soil on a dry lake at the park, which has the nation's largest gypsum dune field.

Archeologists used radiocarbon dating — a method for determining the age of organic material — to analyze macroscopic seeds found within the fossils, according to the study. The footprints were described to be in "good anatomical definition" with visible heel impressions and toe pads.

The scientists researched fauna and aquatic material in areas where the fossils were found, which also helped to estimate dates. Findings also raised the theory that early humans practiced sustainable methods in tending to megafauna initially, scientists said.

"Unlike cultural artifacts, modified bones, or other more conventional fossils, footprints have a primary depositional context and are fixed on the imprinted surface," the report states. 

Researchers note that accurately dating the first people to arrive and live in the Western Hemisphere is still "uncertain and contested." "What we present here is evidence of a firm time and location when humans were present in North America," the report said.

The Associated Press noted that prior excavations in White Sands National Park have uncovered fossilized tracks left by a saber-toothed cat, dire wolf, Columbian mammoth and other animals from the ice age.