A supernova could be the "quick and dirty" explanation for what may have happened to an early North American culture, a nuclear scientist here said Thursday.

Richard Firestone (search) said at the "Clovis in the Southeast" conference that he thinks "impact regions" on mammoth tusks found in Gainey, Mich., were caused by magnetic particles rich in elements like titanium and uranium.

This composition, the Lawrence Berkeley National Laboratory (search) scientist said, resembles rocks that were discovered on the moon and have also been found in lunar meteorites that fell to Earth about 10,000 years ago.

Firestone said that, based on his discovery of similar material at Clovis sites, he estimates that comets struck the solar system during the Clovis period, which was roughly 13,000 years ago. These comets would have hit the Earth at 1,000 kilometers an hour, he said, obliterating many life forms and causing mutations in others.

"I'm not going to tell you that there's Clovis people on the moon, or that they had a space program," Firestone said. But these particles look "very much like the material that comes from the moon, which is the only place we've found with this same high titanium concentration."

Amateur archaeologist Richard Callaway (search) said he was surprised by Firestone's theory.

"I've always considered myself a pretty open-minded person," Callaway said, while browsing some of the artifacts on display at the conference. "And it's kind of shocking to hear that something from the solar system could have done something like this."

Callaway, an Episcopal priest from Atlanta, said that he and his wife have volunteered at the Topper site in Allendale County for the past two summers.

"To be a part of this ... and find something no human being has touched in 15,000 years — that's something," Callaway said. "That's what I like about what we do. You don't find the next answer. You find the next question."

Earlier Thursday, University of South Carolina archaeologist Al Goodyear (search) lectured on his discoveries at Topper, where he says he has found evidence that man existed in North America much earlier than previously thought. Goodyear showed slides of the many tools he has recovered from Topper, as well as a charcoal strip he discovered in soil two meters beneath a 16,000-year-old level of the site.

"Topper's like a box of chocolates," Goodyear said. "Every time we dig a hole, something new comes up."

As the final event of the four-day conference, partially sponsored by USC, Goodyear will lead attendees on a visit to Topper on Saturday.