Mitochondrial DNA, which is a sort of abridged version of DNA, is passed directly from mother to child, so it's something that can be looked at to trace matrilineal descent.

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.

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.

Increasingly developing countries are asking for aid to help deal with the consequences of climate change, which we don't want to give.

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.

I traveled really to amazing places. I went to the Great Barrier Reef, I went to the Amazon, I went to the Andes, to try to bring people stories of sort of what's going on out in the world and bring this issue alive, in a way, and put it out there.