ROBERT SIEGEL, host: If a time machine could take you back more than 13,000 years, you would see hairy, elephant-like creatures with tusks roaming North America. These mastodons were hunted by some of the earliest people to live here.
NPR's Nell Greenfieldboyce reports that scientists recently learned a bit more about those people by taking a new look at an old mastodon bone.
NELL GREENFIELDBOYCE: This particular mastodon took his last breath in what is now Washington state. His bones rested underground until the late 1970s.
MICHAEL WATERS: It was discovered by accident. A local farmer or rancher that was there, he was excavating with his backhoe. He was creating a stock tank.
GREENFIELDBOYCE: That's Michael Waters, a researcher at Texas A&M University. He says a scientist from Washington State University named Carl Gustafson excavated the bones.
WATERS: What he discovered there was a single mastodon. It was an old adult male. It was lying on its left side.
GREENFIELDBOYCE: The bones had cut marks that suggested humans had butchered the animal. One rib looked particularly interesting. X-rays showed that wedged inside was the point of a spear made from antler or bone. Gustafson dated this archeological site to 14,000 years ago and Waters says the controversy began.
WATERS: It's been debated ever since with some people accepting the site and other people's not accepting the site.
GREENFIELDBOYCE: At the time, most scientists didn't believe humans lived in North America that early. Others said maybe that's not even a spear point.
WATERS: You know, it was suggested at one point that this may have been an elk antler tine that somehow got into the bone like there was an angry elk that charged the elephant.
GREENFIELDBOYCE: The controversy lingered for decades. Waters wanted to revisit it using modern technologies, so he called Gustafson. The now retired professor went to his basement, retrieved the rib and put it in the mail. Waters and his colleagues got to work.
WATERS: We can do high resolution CT scanning of the bone and we can even do DNA analysis and that's exactly what we did.
GREENFIELDBOYCE: The CT scans let them build a 3D model of what was stuck inside the bone. Waters says it is a spear point.
WATERS: You could clearly see that the piece had been sharpened to a sharp tip.
GREENFIELDBOYCE: Plus, DNA analysis showed that this spear tip was made of mastodon bone, suggesting the hunters might have taken this material from a previous kill. The research team also confirmed that the ancient hunt happened 13,800 years ago.
Now, this isn't the first evidence that humans were living in the Americas this early. In recent years, scientists have been pushing back the date that people first set foot here, but Waters says they don't know much about those communities of hunter/gatherers.
WATERS: I think what it does is it just provides additional evidence and fills a little bit out about the picture of people here before Clovis.
GREENFIELDBOYCE: Clovis refers to a culture that appeared hundreds of years later. Its hallmark is a beautifully crafted spear point made of stone. Waters says this mastodon kill indicates that earlier people might have relied on bone weapons.
The new findings are reported in the Journal Science. Jonathan Haas is an expert on ancient America at the Field Museum in Chicago. He says the new date on the bones is convincing.
JONATHAN HAAS: And I think that that was an extremely interesting time in North America as people were beginning to colonize an open continent. That's what I think is particularly interesting about this story.
GREENFIELDBOYCE: He says just imagine: America was a wild, still unexplored place where animals like mastodons probably didn't even know to run when they saw a small band of humans creeping closer carrying spears.
Nell Greenfieldboyce, NPR News.
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