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Wednesday, 16 July 2008 19:27

Humans walked America 40,000 years ago

An international team of geoarchaeologists have discovered footprints in central Mexico that place the presence of early humans in the Americas further back than previous thought: around 40,000 years ago. The discovery helps to settle a long-standing debate as to when humans first came to the Western Hemisphere.

British geoarachaeologist Silvia Gonzalez (Liverpool John Moores University (LJMU), in the United Kingdom) lead a team of geoarchaeologists in making this very important discovery on the first presence of humans within the Americas.

The footprints found in rocks (which were once, long time ago, volcanic ash) helps to confirm that humans were in the Valsequillo Basin of central Mexico around 40,000 years ago.

The Gonzalez team is part of the research program called Environmental Factors in the Chronology of Human Evolution and Dispersal (EFCHED), which is part of the Natural Environment Research Council.

The researchers mapped and scanned the footprints using three-dimensional (3D) laser technology. The scans were later reproduced at sub-millimeter precision at the University of Bournemouth using rapid-proto-typing technology.

Specifically, Gonzalez, David Huddart (also with LJMU), and Matthew Bennett (Bournemouth University) found 269 footprints--both from animals and humans--in an abandoned quarry close to the Cerro Toluquilla volcano, located in the Valsequilio Basin, near the city of Puebla, about 80 miles (130 kilometers) southeast of Mexico City.

According to the Liverpool John Moores University article “The Oldest American: Footprints from the Past: Will a footprint rewrite the history books?”, Gonzalez stated, "The footprints were preserved as trace fossils in volcanic ash along what was the shoreline of an ancient volcanic lake. Climate variations and the eruption of the Cerro Toluquilla volcano caused lake levels to rise and fall, exposing the Xalnene volcanic ash layer."

The discovery is important to finding out the first presence of early humans in the Americas because a fierce debate has raged as to when such humans first set foot in the Western Hemisphere. Previous estimates placed humans in the Western Hemisphere around 20,000 years ago.

Based partially on this discovery, Gonzalez states, “We think there were several migration waves into the Americas at different time by different human groups.” [LJMU]

David Huddart, a member of the team making this exciting discovery, provides further comments on page two about the debate on early human presence in the Americas.

Dr. David Huddart further explains the debate on early humans in America when he states, "Most early human occupation sites in the Americas date to the latest Pleistocene or Ice Age, between 10,000 and 12,500 years ago. The existence of 40,000 year old human footprints in Mexico means that the 'Clovis First' model of human occupation can no longer be accepted as the first evidence of human presence in the Americas." [LJMU]

He continues, “New routes of migration that explain the existence of these much earlier sites now need urgent consideration. Our findings support the theory that these first colonists may perhaps have arrived by water rather than on foot using the Pacific coast migration route." [LJMU]

The finding by the Gonzalez team confirms other samples found in the Valsequillo Basin. These samples were unable to determine how long they had been in the region because they were discovered in layers of mixed gravels that were of several different time-periods.

Luckily for Gonzalez, the footprints her team found were not contaminated with materials from other times.

The footprints were thought by the researchers to have been made when these early Americans walked across the shoreline of the volcanic lake. The footprints were covered with volcanic ash and other sediments from the lake.

(The LJMU article stated that the volcanic ash is very hard and, today, is used as concrete, what is called Xalnene ash, for building materials.)

The footprint-and-volcanic-ash mixture then hardened before becoming contaminated with other gravels from other eras, as with the case with the samples from other studies. The footprint-ash mixture eventually submerged in water, which preserved them.

The discovery by Gonzalez and her colleagues was presented at the May 27-30, 2008 joint assembly of the American Geophysical Union in Fort Lauderdale, Florida, United States.

The discovery by the Gongalez team helps to settle the debate on the time-period that early humans first came to the Americas. The debate has been ongoing for over one hundred years.

Currently, the Gongalez team is extending their research of the footprints in order to learn more about them. They expect to conduct further investigations, including calculating such physical characteristics as the height, pace, and stride of these very early immigrants to America.

Further information is found at the MexicanFootprints.co.uk’s website “The Oldest American? Footprints from the Past."

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