Butchery marks can be seen on the ribs of the mammoth. The upper rib is fractured by blunt force impact, the middle rib is stab wound, and the lower rib is knife scar. (Timothy Rowe et al., University of Texas at Austin)
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AUSTIN, Texas — The surprising discovery of a mammoth fossil in a paleontologist’s backyard has led to an even more unexpected discovery.
Remains of female mammoths and their calves from around 37,000 years ago show clear signs of slaughter, providing new evidence that humans may have arrived in North America earlier than thought.
Paleontologist Timothy Rowe first learned of the fossils in 2013, when a neighbor noticed something sticking out of a hillside on some Rowe property in New Mexico.
Upon closer inspection, Luo found a long tusk, a bumped mammoth skull and other bones that appeared to have been broken on purpose. He believes this is where the two mammoths were slaughtered.
“What we have is amazing,” Rowe said in a statement. “It’s not a glamorous place with a beautiful skeleton next to it. It’s all ruined. But that’s what the story is about.”
Rowe, a professor at the University of Texas at Austin’s Jackson School of Geosciences, is an expert in vertebrate paleontology and doesn’t usually study mammoths or early humans. But because of the location of the discovery, he couldn’t resist the study.
Two six-week excavations were conducted at the site in 2015 and 2016, but analysis in the lab took longer and is still ongoing, Rowe said. He is the lead author of a new study analyzing the site and its impacts, published in the journal Frontiers in Ecology and Evolution in July.
What we have is amazing. This is not a glamorous website with a beautiful skeleton next to it. It’s all messed up but that’s what the story is about.
—Paleontologist Timothy Rowe
“I haven’t fully dealt with the cosmic coincidence of this site appearing in my backyard,” Rowe wrote in an email.
Multiple finds at the site paint portraits of what happened there thousands of years ago, including skeletal tools, evidence of fires, bones with broken bones and other signs of humans slaughtering animals.
The long mammoth bones were made into disposable blades that were used to break down the carcasses and then used fire to help melt their fat.
According to the study, fractures caused by blunt force can be seen in bones. No stone tools were found at the site, but researchers found thin sliced knives made of bone with frayed edges.
Chemical analysis of the sediment around the mammoth bones showed that the fires were sustained and contained, not caused by wildfires or lightning strikes. There is also evidence of crushed bones and burned remains of small animals, including birds, fish, rodents and lizards.
The team used CT scans to analyze the bone at the site and found puncture wounds that may have been used to drain fat from the ribs and vertebrae. Luo said the humans who slaughtered the mammoths were thorough.
“I’ve excavated dinosaurs that were scavenged, but the pattern of disjointed bones and fractures caused by human slaughter is unlike anything I’ve ever seen,” Luo said.
The most surprising detail of the site is that it is located in New Mexico — where previous evidence suggests that humans did not appear there until tens of thousands of years later.
Tracing early 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 New Mexico one of the oldest sites in North America created by ancient humans, the researchers said.
For years, scientists have debated when early humans first arrived in North America.
The 16,000-year-old Clovis culture is famous for its stone tools. But there is growing evidence that older North American sites were home to pre-Clovis populations with distinct genetic lineages. Older sites have different types of evidence, such as well-preserved footprints, skeletal tools, or animal bones with cuts from more than 16,000 years ago.
“Humans have been in the Americas for more than twice as long as archaeologists have maintained over the years,” Luo said. “This site shows that humans acquired global distribution much earlier than previously understood.”
The site shows that humans acquired global distribution much earlier than previously understood.
—Paleontologist Timothy Rowe
The study shows that the site is in the interior of western North America, suggesting that the first humans arrived as early as 37,000 years ago. These early humans likely traveled on land or coastal routes.
Rowe said he next wants to sample the site for signs of ancient DNA.
“Tim has done an excellent and thorough job representing cutting-edge research,” retired Texas State University professor Mike Collins said in a release. “It’s forging a path that others can learn and follow.”
Collins was not involved in the study. He led research at the Gault Archaeological Site near Austin, Texas, which contains Clovis and pre-Clovis artifacts.
“I think the deeper meaning of early human acquisition of global distribution is an important new question to explore,” Luo said. “Our new technique provides nuanced evidence of human presence in the archaeological record, and I suspect that there are other sites of similar age or even earlier that have not been identified.”