Thursday, July 20, 2006
Once upon a time, a 2-ton wombat lumbered across the Australian Outback. Around the same time, mammoths and saber-toothed tigers had the California coastline all to themselves.
Millions of years before any of these animals existed, Tyrannosaurus rex and other colossal dinosaurs ruled the world.
These and some of the other largest and most fantastic creatures ever to walk the planet are long gone, victims of mass extinctions of large beasts. And for reasons poorly understood, often the animals to fill the voids were tiny by comparison.
...Mass extinctions occur with surprisingly regularity over the long haul. During the last 250 million years, there's been a big die-off roughly every 26 million years.
Adam Lipowski, a researcher at Adam Mickiewicz University in Poland, suggests the extinctions might sometimes be driven not by climate change or impacts from space, but by the emergence of super predators...