Ice age footprints suggest North America's first peoples were here earlier than we thought

The discovery of human footprints that date back 23,000 years is reigniting the debate about when humans first settled the Americas.

Thousands of footprints belonging to ancient humans — as well as giant animals like mammoths and giant sloths — have been found in the dried lake beds in White Sands National Park in New Mexico. First discovered in 2009, it took over a decade for researchers to reliably date the footprints, thanks to a treasure trove of ditch grass seeds found in rock above and below the prints.

"Using radiocarbon dating, we can determine how old those seeds are, and determine the age above and below, and the tracks date from around 21,000 to 23,000 [years],"  Matthew Bennett, lead author of the study told Quirks & Quarks host Bob McDonald.

"So people were coming back to White Sands repeatedly for around two millennia."

Previously, researchers believed that humans started to expand into the Americas from Siberia as the last ice age ended, and were established by about 13,000 years ago. But these footprints suggest that humans had settled in well before the ice sheets retreated.

"The traditional model is that people were waiting [in Alaska] until the ice sheets that covered North America from coast to coast began to melt, and then they moved south. But we're suggesting that people probably were in Alaska and moving south before those ice sheets reached their peak. So they got in before the door closed and were isolated," said Bennett.

The study was published in the journal Science.

Matthew Bennett is a Professor Of Environmental And Geographical Sciences at Bournemouth University. You can listen to his full conversation with Bob McDonald at the link above.

Produced and written by Amanda Buckiewicz