(CNN) – The astonishing discovery of mammoth fossils in a paleontologist’s backyard led to an even more unexpected discovery.
The remains of a female mammoth and her calf, some 37,000 years old, show clear signs of the massacre, providing new evidence that humans may have reached North America much earlier than previously thought.
Paleontologist Timothy Rowe learned about the fossils in 2013, when a neighbor discovered something emerging from a hillside on his New Mexico estate.
On closer inspection, Rowe found a tusk, a giant sunken skull, and other bones that appeared to have been intentionally broken. I thought it was the place where two mammoths were butchered.
“What we have is amazing,” Rowe said in a statement. “It’s not an attractive site with a beautiful skeleton on the side. Everything is broken. But that’s the story.”
Rowe, a professor at the Jackson School of Earth Sciences at the University of Texas at Austin, is an expert in vertebrate palaeontology and does not usually study mammoths or early humans. But he couldn’t help but work on the investigation because of the location of the find.
Two six-week excavations were conducted at the site in 2015 and 2016, Rowe said, but laboratory analysis has taken much longer and is ongoing. Rowe is the lead author of a new study providing an analysis of the site and its implications, published in the academic journal Frontiers in Ecology and Evolution in July.
“I have yet to fully address the cosmic coincidence of this appearance in my backyard,” Rowe wrote in an email.
The site’s many finds paint a picture of what happened there thousands of years ago, including bone tools, evidence of fire, broken bones and other signs of human slaughter of animals.
Long mammoth bones were used as disposable knives to break up animal carcasses before the fire helped melt their fat.
According to the study, fractures caused by brute force were observed in the bones. There were no stone tools at the site, but researchers did find scaling knives made from bones with worn edges.
A chemical analysis of the sediments surrounding the mammoth bones showed that the fire was sustained and controlled and not caused by bushfires or lightning. There was also evidence of smashed bones and the cremated remains of small animals, including birds, fish, rodents, and lizards.
The research team used CT scans to analyze the bones in situ, finding puncture wounds that would help drain fat from the ribs and vertebrae. Roe said the humans who slaughtered the mammoths were meticulous.
“I’ve excavated dinosaurs that scavengers ate, but the pattern of bone disintegration and fracture resulting from human carnage was different from anything I’ve seen,” Rowe said.
The most surprising detail of the site is that it is located in New Mexico, and previous tests had indicated that humans were not there until tens of thousands of years later.
Trace the first human steps
Collagen extracted from mammoth bones helped researchers determine that the animals were slaughtered at the site between 36,250 and 38,900 years ago. This age range makes the New Mexico site one of the oldest sites established by ancient humans in North America, the researchers said.
Scientists have debated for years when the first humans arrived in North America.
The 16,000-year-old Clovis culture is famous for the stone tools they left behind. But a growing body of evidence indicates that the oldest sites in North America were home to pre-Clovis populations with a different genetic lineage. Ancient sites contain a different type of evidence, such as preserved footprints, bone tools, or animal bones with cut marks from more than 16,000 years ago.
“Humans have been in the Americas for more than twice as long as archaeologists have for many years,” Rowe said. “This site indicates that humans reached global distribution much earlier than previously thought.”
The location of the site, which lies within the western interior of North America, indicates that early humans arrived 37,000 years ago, according to the study. These early humans may have traveled overland or along coastal roads.
Rowe said he wanted to take samples from the site to look for signs of ancient DNA next.
“Tim has done an excellent and comprehensive job representing cutting edge research,” said Mike Collins, a retired professor at Texas State University, in a statement. “It is forging a path that others can learn from and follow.”
Collins was not involved in the study. He led research at the Gault archaeological site, which contains Clovis and pre-Clovis antiquities, near Austin, Texas.
“I think the deeper meaning of early human achievement of global distribution is an important new question to explore,” Rowe said. “Our new techniques have provided accurate evidence of human presence in the archaeological record, and I suspect there are other sites of similar or even older ages that have not been recognized.”