Spencer Wells

Imagine you're copying a very long document, and occasionally you'll put an A where there should be a C. And that mistake has been translated down through the generations, and more mistakes have accumulated. So the longer the lineage has been in existence, the more mistakes the sequence is going to have.

We spent an enormous amount of time as hominids and as primates living as hunter-gatherers. That is the natural way for us to live, and we're suddenly living in this profoundly unnatural way, and we're still in the process of adapting to it and working out how to live with it.

What if I told you every single person in America - every single person on Earth - is African? With a small scrape of cells from the inside of anyone's cheek, the science of genetics can even prove it.

When people said Africa would change me, I didn't understand what they meant. To see the poverty in the townships, for instance, is overwhelming. I found it heart-wrenching to see young children walking barefoot and hungry in the dirt. I'm the kind of person who wants to change the world right here and now, so I got frustrated.