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New doubts raised about old ‘footprints’

Scientists cast doubt on the nature of footprints discovered in Mexico that suggested humans had arrived in the Americas 30,000 years earlier than previously thought.
The apparent imprint of toes and a heel can be seen in hardened volcanic ash just below the bare foot in this image, taken at an abandoned Mexican quarry.
The apparent imprint of toes and a heel can be seen in hardened volcanic ash just below the bare foot in this image, taken at an abandoned Mexican quarry.LiverpoolJohn Moores University / Bournemouth University / Liverpool John Moores University / Bournemouth University
/ Source: Reuters

Scientists cast doubt on Wednesday on the nature of impressions discovered in Mexico that had been interpreted to represent footprints and suggested that humans had arrived in the Americas far earlier than previously thought.

In 2003, an international team of scientists headed by Silvia Gonzalez of John Moores University in Liverpool, England found what they said were about 250 human and animal prints in a layer of volcanic ash near Puebla, Mexico.

They estimated that early hunters walked across the ash deposited near a lake 40,000 years ago. Prior to that discovery, humans were thought to have arrived in the Americas across a land bridge from Asia about 11,000 years ago.

However, a different group of researchers from the United States and Mexico came to a different conclusion after visiting the site and collecting samples.

"You're really only left with two possibilities," one of the skeptics, Paul Renne of the University of California at Berkeley, said in a statement. "One is that they are really old hominids — shockingly old — or they're not footprints."

Renne and a team of geologists and anthropologists who used an argon dating technique and another method to analyze the age of fossils said they were about 1.3 million years old.

"We conclude that either hominid migration into the Americas occurred very much earlier than previously believed, or that the features in question were not made by humans on recently erupted ash," Renne and his team said in a report in the journal Nature.