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I’ve know that we share 99% of our DNA with chimps. But I haven’t understood what that really means until I read this article about Katie Pollard’s research.

In this conversation with Nova, Pollard puts the numbers in perspective:

Given that our DNA sequence has about three billion “letters” in it, one percent is still a pretty vast territory to search. There are about 15 million human-specific letters that have changed in the last six million years.

Pollard and her team are studying these areas of DNA differences:

It turns out that the vast majority of these fast-evolving sequences are not genes, the parts of our genome that encode proteins. The pieces that have changed the most in our DNA look like they are switches, switches that turn nearby genes on and off. So what makes a human different from a chimp isn’t that we’re made up of different building blocks, different genes, but instead that we’re using those pieces in different ways.

Another thing that was really amazing was that more than half of these fast-evolving switches are near genes that are active in the brain, either in the developing embryo or in the adult brain. In a way, this makes perfect sense, because our brains are essential to a lot of things that make us human: our speech, our culture, religion, even our ability to do science.