The arrival of humans onto the American continent and the great thaw that occurred near the end of the last Ice Age both occurred at roughly the same time, about 11,000 years ago. Until now, scientists were unable to tease apart the two events.
To get around this problem, David Steadman, a researcher at the University of Florida, used radiocarbon to date fossils from the islands of Cuba and Hispaniola, where humans didn't set foot until more than 6,000 years after their arrival on the American continent.
The West Indian ground sloth, a mammal that was the size of a modern elephant, also disappeared from the islands around this time.
"If climate were the major factor driving the extinction of ground sloths, you would expect the extinctions to occur at about the same time on both the islands and the continent since climate change is a global event," Steadman said.