An ancient giant sloth hunt, frozen in time

A remarkable set of fossilized footprints uncovered in New Mexico tell the story of a pursuit that unfolded beside a muddy lakeshore some 10,000 years ago.

Record of a chase

The fossilized prints, found in White Sands National Monument, extend for many metres and appear to show early human hunters stalking a giant ground sloth. Occasionally, the human prints can be seen inside the sloth prints -- suggesting that the humans were following the animal closely, likely in the hopes of moving in for the kill, explains Dr. Sally Reynolds of Bournemouth University.

A herbivore -- but with a deadly swipe

The giant ground sloth was about the size of a modern brown bear, Dr. Reynolds says. The sloths were herbivores -- but one still had to be cautious: With their long arms and enormous claws, they could take a deadly swipe if provoked. At the White Sands site, the fossilized prints suggest that the giant animal occasionally turned to defend itself against the pursuing humans. However, the footprints only record the chase, not the end result -- we don't know if the sloth lived or died.

The giant sloth is no more -- but were we the cause?

It's impossible to say for certain if human hunters were the direct cause of the giant sloth's extinction. We do know, however, that many large mammals, including the mammoth and mastadon as well as the giant sloth -- disappear from the fossil record at around this time, just as humans begin to appear in the region in greater numbers.  These remarkable fossils begin to paint a picture of what life would have been like for these early North Americans, Dr. Reynolds says.