Fossilized footprints show humans made it to North America much earlier than first thought

Jeff Pigati and Kathleen Springer, pictured here, of the US Geological Survey undertook the dating of the footprints.

(CNN)North and South America were the last continents to be settled by humans, but exactly when that started is a topic that has divided archaeologists.

The commonly held view is that people arrived in North America from Asia via Beringia, a land bridge that once connected the two continents, at the end of the Ice Age around 13,000 to 16,000 years ago. But more recent -- and some contested -- discoveries have suggested humans might have been in North America earlier.
Now, researchers studying fossilized human footprints in New Mexico say they have the first unequivocal evidence that humans were in North America at least 23,000 years ago.
    One of the fossilized trackways of footprints dated and analyzed in the study.
    "The peopling of the Americas is one of those things that has been for many years very contentious and a lot of archeologists hold views with almost religious zeal," said Matthew Bennett, a professor and specialist in ancient footprints at Bournemouth University and author of a study on the new findings that published in the journal Science on Thursday.
      "One of the problems is that there is very few data points," he added.

      'Unequivocal'

      Bennett and his colleagues were able to accurately date 61 footprints by radiocarbon dating layers of aquatic plant seeds that had been preserved above and below them. The prints, which were discovered in the Tularosa Basin in White Sands National Park, were made 21,000 to 23,000 years ago, the researchers found.
        The timing and location of the prints in southwestern North America suggests that humans must have been on the continent much earlier than previously thought, Bennett said. The people who made the footprints -- mostly teenagers and children -- were living in New Mexico at the height of the last Ice Age.
        Between 19,000 and 26,000 years ago, a period known as the Last Glacial Maximum, two massive ice sheets covered the northern third of the continent and reached as far south as New York City, Cincinnati and Des Moines, Iowa. The ice and cold temperatures would have made a journey between Asia and Alaska impossible during that time, meaning the people who made the footprints likely arrived much earlier.
        "It's the first unequivocal site and a good data point that places people in the American southwest around the last glacial maximum," Bennett said.
        The footprints were dated by using seeds buried in layers of sediment below and above the prints.