How the Big Freeze Killed the Buffalo.

Byline: William Underhill

Picture a bison. He's curly-headed, low-slung and huge. The male, the largest land animal in North America, may stand two meters high and tip the scales at one ton. Despite this formidable profile, the bison was no match for humans. In the 19th century, hunters brought ecocataclysm to the Great Plains, slashing bison numbers from around 60 million to fewer than 1,000.

Maybe Nature should share the guilt. Scientists now say that the earliest bison population in North America fell victim to a more contemporary scourge: climate change. Alan Cooper, a molecular evolutionist at Oxford University, blames a big freeze, not man, for driving the species to near extinction in prehistory. And the same plunge in temperature may also have wiped out the mammoth, the lion and other species once common on the continent. Says Cooper: "Climate change may be much more destructive than we could have guessed."

The findings, reported in last week's issue of the journal Science, contradict orthodox thinking. The first bison are thought to have strayed into North America up to 130,000 years ago, using the land bridge that connected Siberia ...