一个星球,一次实验(4)

Because the early hunter populations were comparatively small and the animal populations truly monumental as many as ten million mammoth carcasses are thought to lie frozen in the tundra of northern Siberia alone

some authorities think there must be other explanations, possibly involving climate change or some kind of pandemic. As Ross MacPhee of the American Museum of Natural History put it

There's no material benefit to hunting dangerous animals more often than you need to-there are only so many mammoth steaks you can eat. Others believe it may have been almost criminally easy to catch and clobber prey.

"In Australia and the Americas," says Tim Flannery, "the animals probably didn't know enough to run away." Some of the creatures that were lost were singularly spectacular and would take a little managing if they were still around.

Imagine ground sloths that could look into an upstairs window, tortoises nearly the size of a small Fiat, monitor lizards twenty feet long basking beside desert highways in Western Australia.

Alas, they are gone and we live on a much diminished planet. Today, across the whole world, only four types of really hefty (a metric ton or more) land animals survive: elephants, rhinos, hippos, and giraffes.

Not for tens of millions of years has life on Earth been so diminutive and tame. The question that arises is whether the disappearances of the Stone Age and disappearances of more recent times are in effect part of a single extinction event

whether, in short, humans are inherently bad news for other living things. The sad likelihood is that we may well be.