New Delhi, April 26: Fractures and scars on a set of mastodon bones in Southern California point to the presence of mystery humans in America about 130,000 years ago, scientists said today, describing research that hugely pushes back human presence in the New World.
The scientists said the bones, tusks and molars of the mastodon - a species related to elephants that went extinct about 10,000 years ago - were buried alongside stones that appear to have been used as hammers and anvils by unidentified humans.
Archaeologists have until now believed that the oldest records of human sites in North America were about 15,000 years old, although Canadian researchers in January this year reported evidence for human activity on the continent 24,000 years ago.
But the new studies show the so-called Cerutti Mastodon site is more than 110,000 years older and America's oldest known archaeological site. The findings will appear in the journal Nature on Thursday.
"Extraordinary claims need extraordinary evidence - and the mastodon site preserves such evidence," Thomas Demere, a paleontologist and curator of the San Diego Natural History Museum told news conference.
The site had spiral fractured bone and molar fragments, several of the fragments displaying evidence of "percussion" or hammering and the clustering of the bones and the stones in two concentrations also point to human activity.
"The patterns we see taken together lead us to believe that humans were processing these mastodon bones using hammer stones and anvils at this site 130,000 years ago," Demere said.
The mastodon site was discovered in 1992 and various groups of scientists have spent the past two decades trying to date the fossils and study the microscopic damage on bones and rocks.
A US geologist, James Paces, starting in 2014 used a uranium-linked dating method that has helped the scientists determine that the activity on the mastodon bones took place about 130,000 years ago.
"This is a pristine site, it has not been disturbed at all by geological processes," said Steven Hollen at the Centre for American Paleolithic Research and a research team member. "We have conducted experiments, breaking elephant bones with large rock hammers and have produced the same type of fracture patterns."
The scientists say the fractures and other damage to the bones cannot be explained through chewing by carnivores or through the trampling of the mastodon bones by other large animals.
"We can eliminate all natural processes that break bones like this," Hollen said. "We have no evidence of a kill or a butchery site, but people were here, breaking up the bones, removing some of the thick pieces, they may have been extracting marrow for food," he said.
Hollen said other excavated sites in the American plains dated between 14,000 and 33,000 years ago also have masdoton bones with the same patterns.
The San Diego Natural History Museum said in a media release the finding poses a lot more questions than answers. "Who were these people? Are they part of an early - but failed - colonisation attempt? Or is there a long, but as yet, scarcely recognised presence of humans in this hemisphere?"
Archaeologists believe humans entered North America by walking across the Bering Strait about 15,000 years ago. But anthropologist Ariane Burke at the University of Montreal, Canada, and her colleagues in January this year used bone fragments from the Bluefish caves near the Alaska border to argue for human presence in Canada 24,000 years ago.
Scientists cannot yet identify the people who worked on the mastodon bones. Hollen points out that breaking elephant bones with stones is an old technology. "We have people in Africa 1.5 million years ago breaking up elephant limb bones in this pattern and as people moved out of Africa and across the world, they took this technology with them."
