The eruption may have wiped out the ozone layer.
"You haven't lived until you've put your arms around a mammoth femur trying to measure it," Smith said.
A fossil skull was 20 percent bigger than even those of the largest modern lions in Africa.
Surveying four small Russian islands near the shores of Alaska, scientists spotted a grizzly "fence" of bones on the beach that turned up a rare discovery.
Swift parrots are on the brink of extinction, and conservationists are getting desperate.
Demand for "white gold" has taken the elephant to the brink of extinction.