The discovery of an ancient human footprint in the United States has shown that human beings were in the Americas long before archaeologists previously believed.
The fossilised footprint which was found in a lakebed in the US state of New Mexico are dated at 23,000 years old.
Scientists had previously believed that humans first reached the Americas by travelling across a land-bridge from what is now Russia to what is now Alaska, during the last ice age, and it was thought they would have then had to remain in the northern regions due to the presence of huge glaciers. This fossilised footprint shows that humans made their way down the Americas far faster than had ever been suspected.
Sally Reynolds, a paleoecologist at Bournemouth University, said that the finding:
"Definitively places humans in North America at time when the ice sheet curtains were very firmly closed. Then more came down after the ice receded."
The previous oldest footprint in the Americas was discovered in Chile and dates back to 15,600 years ago. In total, the team that discovered the new oldest footprint have discovered 60 footprints in, which are dated by looking at tiny seeds that were trapped in the footprints themselves.
There have been prior suggestions of human activity at earlier dates. Α Mexican cave has been discovered containing tools that could be potentially dated back 32,000 years, however, the method of dating these is imprecise, and they could be from much more recent history.
Theories as to how humans travelled over the great glaciers are merely hypotheses at this time, but some researchers suggest that they could have sailed down the Pacific coast and reached the lands to the south in this manner. Little is known about the sea-faring skills of these early humans.
What is known about these early humans is that they hunted giant sloths, an animal that went extinct 12,000 years ago. Their extinction is likely linked to the arrival of humans and related to over-hunting. Other species, such as woolly mammoths also died out around the same time.
Reynolds says:
"Humans show up and megafauna start dying. It seems like an obvious cause and effect relationship."
[h/t: science alert]
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