Bison DNA Helps Explain Extinctions

Climate and environmental change — not human hunting pressure — served as the primary force that nearly eradicated ancient bison and drove sabre-toothed cats, mammoths and many other large mammals to extinction, a new study suggests in the 26 November 2004 issue of the journal Science.

Both the genetic diversity and the size of bison populations in present-day Alaska, Canada and Siberia — a landmass known as Beringia — underwent a catastrophic decline about 37 thousand years ago, well before large numbers of humans arrived in the New World, the scientists found. This diversity drop and population crash occurred at a time of environmental and climatic flux just before glaciers moved across much of North America.

Beth Shapiro and colleagues used mitochondrial DNA sequences from approximately 350 fossilized bison bones to record evolutionary processes from the Late Pleistocene "in real-time." In addition to extinction insights, their analysis shows that today's North American bison are descended from a small population isolated south of a glacial ice barrier that formed in central North America approximately 20 thousand years ago.

— Daniel B. Kane

29 November 2004