Archaic Interbreeding? So What?

Later this week, I will be speaking at the University of South Florida—Saint Petersburg in their lecture series, a Celebration of the Genome.” My topic is “Finding the Human in the Genome.”

I start with the obvious: Our knowledge of human biology is increasing rapidly, thanks in large part to the Human Genome Project. We can now compare the DNA of one human being with another and ask questions about similarities and differences. We can compare human DNA with the full genomes of chimps and other species.

Most interesting to me is that we can also compare the genome of anatomically modern humans with that of extinct forms of humanity, such as Neandertals or their recently discovered cousins, the Denisovans. What we have found is that in a real sense, they are not extinct at all because their DNA lives on in us.

That leads to something less obvious but more profound. The more we know about human biology, the less we know about human nature. Put another way, the more information we have, the less confident we are that we really know what we mean when we talk about “humanity.”

So what is going on here? Does it really bother anyone—besides me, that is, and perhaps only because I am, after all, a “theologian”? I am asking myself this question a lot these days. Does it really matter that our ancestors interbred with Neandertals and Denisovans and, as time will probably tell, many other forms of archaic humanity?

So what’s the big deal? In some ways I guess it’s like the high school student who runs a paternity test and learns that daddy isn’t daddy.

Or maybe it’s more like this. Years ago, I remember hearing Kári Stefánsson speaking to a roomful of scientists and introducing deCODE Genetics, the Iceland DNA database. He explained the reasons for the project, such as excellent health records, small genetic diversity, and superb genealogical records going back 1,000 years. We Icelanders need to sell more than fish, he said. We want to mine our DNA for all kinds of gene-disease information. Then Stefánsson mentioned that the information sometimes disproved the genealogies. Everyone laughed when he said: “We are not responsible for what our Viking ancestors did back then during the long Icelandic winters.”

Is that it? Is that all that’s happened here, just some forced revisions of the family tree? So what if my ancient ancestors were not exactly what I thought? It happened, after all, some 40,000-100,000 years ago. I am not responsible.

But I am affected. My biology is different from what I once thought. Perhaps I am healthier as a result of the ancient interbreeding, as at least one report has suggested.

More than that, I am coming to see human beings as biologically more diverse and more complicated that we once thought. The diversity part is a bit scary. We have not done well as a species in dealing with our differences.

The complexity part—that’s more of a mystery than a fear. I don’t claim to hear the voices of my Neandertal ancestors calling out from my DNA or reverberating through my metabolic processes. At least not yet.