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Fossil footprints show humans in North America 11,000 years earlier than previously thought

New fossil evidence has rewritten the history of humans in North America, with footprints dating the first know human activity on the continent as far back as 23,000 years ago.

That is 11,000 years more – almost double – than the previously thought date of 12,000 years ago, according to research published in the journal Science on Thursday.

It places humans in the Americas before the last Ice Age, rather than after the ice sheets began melting, said Dr Sally Reynolds, a principal academic in hominin paleoecology at Bournemouth University.

The fossilised footprints were found at White Sands National Park in New Mexico in the soft mud of an ancient lake that is now part of the Alkali Flat.

"The oldest footprints in the Americas date to our site at White Sands at 23,000 years, which is a time where the ice sheets basically were at their maximum," Dr Reynolds said.

© NPS, USGS and Bournemouth University: Fossilized footprints found in New Mexico

"We thought that the humans could only travel down after the ice sheet receded, so we’re at about 12,000 years, and so for a long time many of the sites were thought to be capped by that maximum age when the ice-free corridor opened and the humans were able to travel down south."

The footprints were first discovered by David Bustos, a resource manager at the National Park, when he heard about "ghost tracks" – footprints that would appear when the ground was wet and disappear when it was dry.

Scientists first confirmed the fossilised footprints were real in 2016, and carbon dating of aquatic plan seeds around the footprints published in Science this week placed the tracks to between 21,000 to 23,000 years ago.

Most of the tracks were left by teenagers and younger children, plus a few adults, surrounded by tracks of mammoths, giant ground sloths, and dire wolves.

Dr Reynolds said the discovery also has implications for the history of megafauna on the continent, with their extended co-existence alongside humans suggesting they survived longer before dying out from overhunting.

"It may well be that the humans were harvesting these megafaunas as part of their killing and their hunting more sustainably in the earlier years," Dr Reynolds said.

"And potentially through time as the populations grew, the balance of power shifted and the humans started overharvesting these mega faunas and that might have contributed to their demise." 

Reference: Independent: Justin Vallejo