Fossilized footprints of humans, who are supposed to have lived some 23,000 years ago were found in New Mexico, reported AP. The discovery indicates that humans were walking across North America during the period and is expected to give researchers some clue about a mystery that has long intrigued them-When did people first arrive in the Americas, after dispersing from Africa and Asia?

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Most scientists believe ancient human migration made its way into the continent by a now-submerged land bridge that connected Asia to Alaska. Some researchers have offered a range of possible dates for human arrival in the Americas, from 13,000 to 26,000 years ago or more based on various historical evidence like stone tools, fossil bones and genetic analysis.

However, the current discovery and the study that followed gives a more solid timeline about humans’ definite presence in North America. Although it also rooms for the fact that they might have arrived earlier in the region, the authors say.

 “Fossil footprints are more indisputable and direct evidence than cultural artefacts, modified bones, or other more conventional fossils,” researchers wrote in the journal Science, which published the study Thursday.

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“What we present here is evidence of a firm time and location,” they said  

On the basis of the size of the footprints, researchers believe that early human migration into the region also included children and teenagers and that they lived during the early ice age.

The footprints were first spotted by David Bustos, the park’s resource program manager in a dry lake bed in White Sands National Park in 2009. He and others found more in the park over the years.

After that scientists at the US Geological Survey recently analyzed seeds stuck in the footprints to determine their approximate age, ranging from around 22,800 and 21,130 years ago.

“We knew they were old, but we had no way to date the prints before we discovered some with (seeds) on top,” he said Thursday.

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Made of fine silt and clay, the footprints are fragile, so the researchers had to work quickly to gather samples, Bustos said.

“The only way we can save them is to record them — to take a lot of photos and make 3D models,” he said.

Earlier excavations in White Sands National Park have uncovered fossilized tracks left by a saber-toothed cat, dire wolf, Columbian mammoth and other ice age animals.

(With inputs from Associated Press)