10,000-year-old skeleton challenges theory of how humans arrived in Americas

A 10,000-year-old skeleton discovered in Mexico has challenged the “traditional” theory that humans first entered the American continents as a single population, scientists say.

An analysis of the remains, found in an underwater cave known as Chan Hol near the city of Tulum, suggests there may have been multiple groups of early American settlers arriving “from different geographical points of origin”.

According to the researchers, the skeleton, named Chan Hol 3, belonged a 30-year-old Paleoindian woman.

Paleoindians were the first peoples to arrive, and subsequently inhabit, the Americas.

It is believed they journeyed across an ancient land bridge connecting Asia to North America, known as Beringia, during the last Ice Age more than 12,000 years ago, before migrating to the Patagonian region in South America.

The researchers say the shape and structure of the Chan Hol 3 skull is different to some of the other skeletons from a similar time period, indicating at “least two morphologically different Paleoindian populations”.

Dr Silvia Gonzalez a professor of quaternary geology and geoarchaeology at Liverpool John Moores University, and one of the study authors, told the PA news agency: “The new results are important because they question the ‘traditional model’ for the peopling of the Americas with one single and homogeneous Paleoindian population migrating very fast from Beringia to Patagonia after 12,000 years ago.

“Our results indicate that at least two morphologically different Paleoindian populations were coexisting in Mexico between 12,000 to 8,000 years ago, one in Central Mexico and the other in the Yucatan Peninsula.”

The team, led by Professor Wolfgang Stinnesbeck, an earth scientist at Heidelberg University, dated the skeletal remains using mineral deposits called flowstone which covered some finger bones.

They believe Chan Hol 3 to be at least 9,900 years old, if not older.

Structural analysis revealed Chan Hol 3 had a round head with broad cheekbones and a flat forehead, resembling three other skulls from the Tulum caves.

But according to the researchers, her cranial characteristics are different to the long-headed Paleoindian skeletons found in the region.

Dr Gonzalez added: “The Tulum skeletons may indicate that either more than one group of humans originally reached the American continent from different geographical points of origin, or that there was sufficient time for a small group of early settlers living in isolation on the Yucatan Peninsula, to develop a different skull morphology.

“In either case, the early settlement history of the Americas appears to be more complicated and may date back thousands of years earlier than commonly believed, according to the new human morphology data.”

The findings are described in the journal PloS One.