Today, when we look at a brain, we see an intricate network of billions of neurons in constant, crackling communication, a chemical labyrinth that senses the world outside and within, produces love and sorrow, keeps our hearts beating and lungs breathing, composes our thoughts, and constructs our consciousness.

We may be sucking in all sorts of viruses and we really don't know the full range of them. Maybe we've got flu virus inside of us. That's a possibility. Maybe we're part flu.

Evolution has led to some populations of people being able to digest milk without much trouble when they're adults as well.

If you're looking for your own idea of your own identity you know the human genome may not be the best place to look for it. You're just looking at a bunch of viruses.

About 1.2% of the human genome is made up of genes, things that encode for proteins, the stuff that we consider us. There is about 8.3% that's a virus. In other words we're probably about seven times more virus than we are human genes, which is kind of a weird way to thinking about yourself.

I wouldn't be a very good hunter without these glasses. I'm not a very good hunter with these glasses, but I'd be even worse without them, so that would put a crimp in how many kids I could have, so all of these medical advances have at least in some parts of the world blunted natural selection.

Viruses don't just make us sick. They can actually sometimes end up in our genomes.