A popular Darwinian meme is that humans and chimp genomes are ninety-something percent identical. It varies a bit, but usually hovers close to 99%. The meme hides all sorts of assumptions, of course, but the take home lesson for the headline reader is plain enough: we’re almost exactly the same as chimps.
Though the 99% number has received some qualifiers, and has even been referred to as a “myth” in Science, the basic idea remains firmly entrenched in the media collective consciousness.
But evidence seems to be piling up that the similarities are not nearly what has been advertised. Geneticist Richard Buggs has reflected on this, and has even predicted “that when we have a reliable, complete chimpanzee genome, the overall similarity of the human genome will prove to be close to 70% (and very far from 99%).”
It will be interesting to see how Buggs’ prediction holds up over time. If he’s right, this will be one more switch from “meme” to “myth” in the Darwinian ledger.
I should confess that I haven’t followed this debate closely, simply because I don’t think that the meme, even if true, really shows much. Here’s what I mean. Some years ago, a reporter called the Discovery Institute asking for a comment on a new study showing a 75% genetic similarity between human beings and a nematode (if I remember correctly). The reporter asked me what I thought about the discovery that we were 75% identical to a nematode. I suggested that there was a difference between our genomes being quite similar to the nematode’s, and human beings being quite similar to nematodes. That didn’t seem to connect, so I said: “Well, why doesn’t the story cause you to reassess the assumption that we’re basically identical with our DNA? If somebody told me we were 100% chemically identical with chimps, I would conclude that we must be a lot more than mere chemicals, since chimps and humans are quite different. Now since humans and nematodes are obviously quite different, while our genomes are similar, doesn’t that suggest that genetics tells us less about ourselves than we had assumed?” I’m pretty sure my comments didn’t make the story.