Wooly mammoths, sabre-toothed tigers, and giant cave bears lived alongside man during the Ice Age. But while humans persisted, these big beasts–along with other “megafauna”–became extinct. Scientists had suggested that their demise was caused by a comet or asteroid impact that left tiny traces in upper-level rock layers around the world, but new research gives this Ice Age-ending scenario a cold shoulder.

In a study published in the Proceedings of the National Academy of Sciences, a team of British and American scientists refuted the last remaining piece of evidence supporting this particular impact theory–nanodiamonds. If impacts led to the extinction of the Ice Age megafauna, the resulting heat would have turned some organic carbon into tiny diamonds.

Study co-author Andrew Scott of Royal Holloway University of London told BBC News, “We looked for these diamonds and we couldn’t find them.”1 Scott and his colleagues looked in layers that were deposited during a time called the Younger Dryas, also referred to as the last “Big Freeze.” Although temperatures were not as low then as they had been during earlier, and much more intense, phases of the Ice Age, they were nonetheless quite cool.

Since Scott and lead author Tyrone Daulton found no diamonds, they suggested that earlier claims of finding the diamonds were incorrect. They called for scientists to abandon the idea that impacts caused Ice Age extinctions.

But BBC News reported Douglass Kennett of the University of Oregon–a long-time impact theory supporter–as saying, “The Daulton et al claim that we have misidentified diamonds is false and misleading.” And geosciences consultant Allen West stated that more evidence for nanodiamonds and the impact theory would be published in the near future.1….

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