Neanderthals were pretty smart, and if we actively killed them off, then probably we did so in the same way that humans kill each other.

Some of these species that are now no longer with us were killed off by a fungal disease that was moved around the planet by people.

You're an animal that needs to move across the landscape, you can't anymore, and that's another way we're just changing the surface of the Earth in very dramatic ways.

When you drive to the grocery store, your intention is not to change the world, it just happens to have that impact. So we've done a lot of things without even realizing it, and yes, just being unusual, as you say, does not put you above, in a sense, any of the other organisms with whom we share this planet.

Most of the world's major waterways have been diverted or dammed or otherwise manipulated - in the United States, only two per cent of rivers run unimpeded - and people now use half the world's readily accessible freshwater runoff.

Several decades ago, a detachment of the American right cut itself loose from reason, and it has been drifting along happily ever since. If the birthers are more evidently kooky than the global-warming "skeptics" or the death-panellers or the supply-siders or the Swift Boat Veterans for Truth, they are, in their fundamental disregard for the facts, actually mainstream.

There are a lot of things that we could do to minimize what we're doing, but we're not getting back those frogs that I saw that no longer exist.