Walking with ancestors: discovery rewrites American prehisto

Early Americans linked to Aborigines
By David Keys

London
July 5, 2005 - 1:29AM


The discovery of 40,000-year-old human footprints in Mexico may link early Americans to Australia's Aborigines.

Archaeologists said yesterday the footprints showed that mankind colonised the New World at least 40,000 years ago, 25,000 years earlier than previous estimates.

The new evidence - 269 human footprints preserved in ancient volcanic ash - was discovered by Mexican and British archaeologists near the Mexican town of Puebla, 120 kilometres south-east of Mexico City.

"The discovery of the footprints in Mexico is, I believe, important because it shows that humanity's spread across the world was much faster than previously thought," said one archaeologist, Sylvia Gonzalez, from John Moore's University in Liverpool.

"The new discovery also gives additional support to the idea that the very early first Americans may well have been of Australoid type closely related to the Australian Aborigines."

She said the footprints showed that early humans adapted to new environments much quicker and more easily than previously thought.

Until now the earliest definite archaeological dates for a human presence in the Americas is around 15,000 years ago in various parts of North and South America.

Dr Gonzalez said that because the new footprints showed humans were in southern Mexico up to to 39,000 years ago, and because human migration takes centuries, humans must have entered the Americas more than 40,000 years ago.

Dr Gonzalez said the new discovery suggested that humans may have entered the Americas during a slightly less cold phase.

The Oldest American?
Footprints from the Past




Right human footprint, showing toe
impressions and typical figure of eight shape


Human left footprint showing toe impressions and
slight heel impression. Modern size 43 for scale



The discovery of 40,000 years old human footprints in Central Mexico challenges accepted theories on when and how humans first colonised the Americas.



The timing, route and origin of the first colonisation of the Americas remains one of the most contentious topics in human evolution. Experts from many disciplines are searching for the answers to three seemingly straightforward questions:


• From where did the first people come?


• How did they enter the Americas?


• When did they arrive?



Until recently archaeologists thought they had the answers to these questions. Evidence suggested that the Americas had been colonised towards the end of the Pleistocene period by hunter-gatherers migrating from Siberia into Alaska across the Bering Land Bridge, an exposed continental shelf, when sea levels were lower. This is known as the Clovis-First Model.



According to this model the earliest occupation of the Americas began 11,500 years ago.



The discovery of fossilised human footprints in the Valsequillo Basin, Central Mexico challenges this accepted viewpoint and provides new evidence that humans settled in the Americas as early as 40,000 years ago.




Location of Mexico and Mexico City



Location of the modern Valsequillo reservoir and
Cerro Toluquilla south-east of Puebla.



Toluquilla quarry and the upper surface of the
Xalnene Ash where the footprints are preserved.

The footprints were discovered in the summer of 2003, on the floor of an abandoned quarry by Dr Silvia Gonzalez, Professor David Huddart (Liverpool John Moores University) and Professor Matthew Bennett (Bournemouth University). At the time of the discovery the team were working on dating and mapping the geology of the Valsequillo Basin, Puebla, Mexico.



Dr Gonzalez is one of a growing number of scientists who believes that the first Americans may have arrived by water rather than on foot, island hopping along the Pacific coast. CLICK HERE

Possible migration routes by humans into the
Americas, with some important sites noted.

Until recently archaeologists thought they had the answers to these questions. Evidence suggested that the Americas had been colonised at the end of the last Ice Age during the Pleistocene period by hunter-gatherers migrating from Siberia into Alaska across an exposed continental shelf, the Bering Land Bridge. This is known as the Clovis-First Model.



The discovery of new evidence, such as the prehistoric footprints in the Valsequillo Basin, points to the presence of humans in the Americas much earlier than many originally thought. A growing number of scientists, including Dr Silvia Gonzalez, who leads the footprints research, also believe that these first colonists may have arrived by water rather than on foot using the Pacific Coast Migration Route.

Why are the footprints important?

Top of the Xalnene Ash and
the overlying lake sediments,
Toluquilla quarry wall



Left human footprint on the Xalnene
ash, Toluquilla quarry.



Left human footprint, showing figure of
eight shape, Toluquilla quarry


The Xalnene ash layer must have been exposed at some point during a period of low lake level, creating a new shoreline. The early Americans walked across this, leaving behind footprints. It is likely that changes in climate along with eruptions of the Cerro Toluquilla volcano led to rises in the level of the lake after the ash fall. This resulted in the quick burial of the footprints by lake sediments and their subsequent preservation. Hence, detailed work into the palaeoclimate and palaeoenvironmental conditions in the basin is crucial to our understanding of the nature of the footprint site. This work is currently being undertaken by a team of palaeoenvironmental scientists (Dr Rhiannon Stevens, Prof. Melanie Leng (NERC Isotope Geosciences Laboratory and University of Nottingham), Prof. Sarah Metcalfe (University of Nottingham), Dr Angela Lamb (NERC Isotope Geosciences Laboratory) and Dr María del Socorro Lozano García (Universidad Nacional Autónoma de México (UNAM)). Click here for further information: http://www.geog.nottingham.ac.uk/~metcalfe/