Creatures adapt to changing environments ... the fact that at the end of the Permian Period they were gone seems unthinkable.

About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. Less than 5 percent of the animal species in the seas survived. On land ...

Toward the end of the Permian period, Earth was reeling from ... where the die-offs of certain predator and competitor creatures allow one surviving group of organisms to go gangbusters.

Some have proposed that the disappearance of certain predators and competitors allowed some of the surviving creatures to thrive. And others have proposed that the climate changes associated with the ...