More than four decades ago, a set of fossilised footprints were discovered during highway construction work in northeastern Mexico, about 300 kilometres from the Texas border. They were excavated and taken to a local museum where their precise location became lost to history. Now for the first time since their discovery in 1961, archaeologists have been able to date the footprints, and they are the oldest tracks ever discovered in North America .

Dr Nicholas Felstead, a geoarchaeologist at Durham University led a new analysis of the prints and were able to date the tracks because they were preserved in travertine, a sedimentary rock that contains minute traces of uranium from the waters in which it formed. Since uranium decays at predictable rates, the scientists were able to determine the fossil’s age. Their results showed that the footprints are about 10,550 years old.

“To my knowledge the oldest human prints previously reported in North America are around 6,000 years old, so the … prints pre-date these by some 5,000 years,” said Dr. Felstead.

Scientists know that the footprints come from the Cuatro Ciénegas Basin, a marshy, spring-fed desert refuge, but the exact location is still unknown. An additional 11 tracks have been found in the basin, and these have been dated to about 7,200 years. “So our reported footprint date is not only the oldest human fossil evidence, but also the oldest archaeological evidence, reported from the Cuatro Ciénegas Basin,” Felstead said.

The region where the tracks were found is known to have been home to the Coahuiltecans, a diverse group of nomadic hunter-gatherers that ranged from central Mexico to the Texas plains. Little is known about the centuries in which they that they inhabited certain areas, so the latest findings provide valuable insights into the Coahuiltecans. The oldest previously reported human fossil evidence coming from the Coahuiltecans dates back about 9,000 years, so archaeologists now know that they inhabited the area much earlier.

The oldest known human print in the Western Hemisphere is the tiny track of a child’s foot in Chile dated to 13,000 ago — adding fuel to the ongoing debate about when humans first migrated to the New World.

By April Holloway