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.

Of the many species that have existed on earth - estimates run as high as fifty billion - more than ninety-nine per cent have disappeared. In the light of this, it is sometimes joked that all of life today amounts to little more than a rounding error.

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.

There's this idea of shifting baselines. It was coined by a guy named Jeremy Jackson. It's the idea that every generation takes what it sees, and says, "Okay, well, that's the norm."

Though it might be nice to imagine there once was a time when man lived in harmony with nature, it’s not clear that he ever really did.

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.

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.