Rebutting a speculative hypothesis that comet explosions changed Earth’s climate sufficiently to end the Clovis culture in North America about 13,000 years ago, Sandia lead author Mark Boslough (Discrete Mathematics & Complex Systems Dept.) and researchers from 14 academic institutions assert that other explanations must be found for the apparent disappearance. “There’s no plausible mechanism to get airbursts over an entire continent,” said Boslough, a physicist. “For this and other reasons, we conclude that the impact hypothesis is, unfortunately, bogus.”

Sandia National Laboratories’ Mark Boslough rebuts a speculative hypothesis about comets leading to the end of the Clovis culture in North America.

In a December 2012 American Geophysical Union monograph, first available in January, the researchers point out that no appropriately sized impact craters from that time period have been discovered, nor have any unambiguously “shocked” materials been found. In addition, proposed fragmentation and explosion mechanisms “do not conserve energy or momentum,” a basic law of physics that must be satisfied for impact-caused climate change to have validity. Also absent are physics-based models that support the impact hypothesis. Models that do exist, write the authors, contradict the asteroid-impact hypothesizers.

In a widely reported press conference announcing the Clovis comet hypothesis in 2007, proponents showed a National Geographic animation based on one of Boslough’s simulations as inspiration for their idea. Confronted by apparently hard asteroid evidence, as well as a NOVA documentary and an article in the journal Science, all purportedly showing his error in rebutting the comet hypothesis, Boslough ordered carbon dating of the major evidence provided by the opposition: nanodiamond-bearing carbon spherules associated with the shock of an asteroid’s impact. The tests found the alleged 13,000-year-old carbon to be of very recent formation. “I never said the samples were salted,” Boslough said carefully. “I said they were contaminated.” That find, along with irregularities reported in the background of one member of the opposing team, was enough for NOVA to remove the entire episode from its list of science shows available for streaming, Boslough said.

“Just because a culture changed from Clovis to Folsom spear points didn’t mean their civilization collapsed,” he said. “They probably just used another technology. It’s like saying the phonograph culture collapsed and was replaced by the iPod culture.”

Read the Sandia news release.