[an error occurred while processing this directive] BBC News
watch One-Minute World News Last Updated: Thursday, 25 November,
2004, 19:29 GMT Bison shed light on big wipeout North American
bison, Steve Maslowski/US Fish and Wildife Service The human
hunting theory has been left out in the cold New evidence casts
doubt on the theory that sabre-toothed cats, mammoths and other
big North American mammals were driven to extinction by human
hunting.  Genetic analysis of bison remains shows their
populations started to crash around 37,000 years ago - long
before humans arrived in the New World.  Researchers claim that
climate change and other factors are more likely culprits in the
extinction.  An international team has published its findings in
Science magazine.  Date conflict  Until as recently as 20,000
years ago, North America had a range of large mammals to rival
the wildlife of present-day Africa.  The continent was home to
woolly mammoth and mastodon, horses, camels, giant ground sloths
and bear-sized beaver