More Death From Above

A new study says a comet did to the mammoth what an asteroid did to the T-rex:

Space rocks that slammed into the glaciers of eastern Canada some 12,900 years ago likely helped wipe out mega-animals like woolly mammoths and possibly the continent’s first human inhabitants called the Clovis people, according to a new study that adds to evidence that a trio of factors were involved.

The new evidence comes from recently discovered nano-sized diamonds, which researchers say are the strongest clues to date for an argument that could explain the region’s die-off during the late Pleistocene epoch.

This still isn’t a silver bullet. Like the overkill hypothesis, it doesn’t explain why some American megafauna went extinct while others — bison, moose, bighorn sheep — live on to this day.

I interviewed John Harris, the chief curator at the Page Museum in Los Angeles, a few years ago for a story. He told me that Pleistocene juniper twigs pulled from the brea showed distinct evidence of carbon starvation. This suggested that plant resources were diminished, which in turn affected herbivores and their predators. “When you review the herbivores that survived you’ll note they comprise ruminants (bison, deer) and omnivores (peccaries). Horses, ground sloths and proboscideans are hind-gut fermenters that failed to survive,” Harris said. If you’ve ever walked behind a horse, you know it leaves a lot of undigested plant matter in its path. Cud-chewers digest plants more efficiently; omnivores have a greater variety of food on which they can live.

Did the atmospheric results of the comet cause carbon starvation? So far so good, but it still doesn’t explain megafauna extinctions in other parts of the world. What I really want to know is why horses went extinct in North America but survived in Eurasia. Was the comet felt here more than there?