Re-examined mastodon site opens a window to lost world
Updated 8:11 am, Friday, October 21, 2011
Since the spectacular 1977 discovery of a mastodon's remains in Washington state scientists have argued about who or what killed it some 14,000 years ago.
But his view lay outside the more conventional view, which held that humans could not have been involved in the death of the mastodon, a species related to woolly mammoths. At the time most archaeologists didn't even believe humans had arrived in North America that long ago.
On Thursday, Gustafson received some measure of vindication with the publication in the journal Science of an article concluding that humans had indeed killed the mastodon.
"My colleagues at the university would not accept the theory," Gustafson, now retired, recalled. "When you're working side-by-side with them in the same building and they don't even believe you, well, you get very discouraged."
Eventually his grant funding ran out, and by the early 1980s only his son remained to work the site with him.
So he waited. And waited. Until the phone rang a few years ago, when Texas A&M University's Michael Waters called and said he wanted to reanalyze the remains Gustafson had found.
In the three decades since the mastodon discovery the tools of scientific discovery have undergone a CSI-like transformation. Waters wanted to use the new powerful analytical tools to determine whether humans may have indeed killed the mastodon.
The key piece of evidence behind Gustafson's human-caused death theory was a rib bone with another bone embedded in it. A fuzzy, two-dimensional X-ray at the time proved inconclusive, but Gustafson believed the bone had been shaped into a weapon-like point by early Americans hunting large game.
Waters used a high-resolution CT scanner, which took an image every two-thousandths of an inch, to create a three-dimensional image that showed a weaponized bone embedded in the mastodon's rib.
"The tip of a bone projectile point was as clear as day," Waters said.
The next step was to figure out the origin of the bone point. Protein and DNA analysis of the bone showed that the bone point itself was fashioned out of a mastodon bone.
Finally Waters and his team performed a modern radiocarbon dating analysis to confirm that the mastodon died 13,800 years ago, plus or minus 50 years.
"Clearly these people were hunting mastodons, and probably harvesting their bones to make tools," Waters said. "It adds one more piece to the puzzle of trying to understand the first Americans. It's filling out our picture."
It's a picture that's been radically remade in recent years.
Since the 1930s, archaeologists had believed the ancestors of the Clovis people - so named for a small number of stone "points" found near Clovis, N.M. - walked into North America from Asia across the Bering Sea landmass as the last Ice Age waned about 13,500 years ago.
But several finds in recent years, including Waters' excavation of a site just north of Austin, have overturned this theory.
A role in extinction?
This Debra L. Friedkin site along Buttermilk Creek yielded a trove of artifacts that date as far back as 15,500 years ago, suggests the first Americans must have come from Asia, not through an ice-free corridor over land, but along the Alaskan and Canadian coasts in boats as long as 16,000 years ago.
The mastodon site not only bolsters this theory of an earlier peopling of the Americas but also suggests humans may have played a more significant role in the so-called megafauna extinction, in which mastodons, mammoths and other large mammals disappeared from North America between 14,000 and 11,000 years ago.
"These pre-Clovis people were obviously hunting large mammals, and they may have played a role in their extinction," Waters said.
The Washington mastodon site is important to archaeologists because it provides a window into this lost world, when the glaciers were first beginning to melt and humans were putting their first imprint on the then truly new world.
It was a time when hunters used bone points, before later learning to work flint into more durable stone points.
"The old bones are getting a new look," Gustafson said. "This is tremendous. I can't imagine anything nicer to have at this time."
NEW LOOK: A CT X-ray of a bone projectile point embedded in a mastodon's rib proves early Americans killed the animal.