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.

People sometimes say we need to be really almost on a wartime footing if you want to change. Our whole economy is based on burning fossil fuels, which is taking CO2 out of the ground and putting it up into the air.

Even very smart people can try to shoehorn new information that just doesn't fit into an existing paradigm.For a long time the story that we've been telling ourselves is that humans are just another animal. We evolved from other animals and our place in the universe isn't particularly special. What I'm trying to convey in my book [The Sixth Extinction] is that we are unusual.

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

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.

The Earth is big. There are huge natural forces that have worked over geological time. But it turns out, when you look carefully at the geological time, you can't find anything like us.

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.