Genomics and Humanity's Future

[Geee]

National Review:

Genomics and Humanity’s Future
A pair of recent discoveries could make it an unhappy one.

The science news this month was dominated by two genome stories. An organism’s genome is the sum total of all its genetic information — its DNA. In sexually reproducing species, a child gets half its genome from one parent, half from the other. Asexual organisms like bacteria just copy DNA from one generation to the next. In both cases, there are occasional copying errors, which serve to make life (as it were) interesting.

The first genome story concerned one of those sexually reproducing species — well, one or two, depending on who’s counting. “Species” is a knotty concept. (Lecture 34 in Jeffrey Kasser’s Philosophy of Science course does its best to untie the knot.)

In the few millennia prior to 30,000 b.c., our remote ancestors in Europe and the Middle East, whither they had spread after leaving Africa, were sharing those territories with an older stock, the Neanderthals. Around 30,000 b.c. the Neanderthals disappear from the archeological record, leaving our ancestors in sole possession of the turf (tundra, whatever). Were we and they separate species — Homo sapiens and Homo neanderthalensis? Or two distant breeds of the same species — Homo sapiens sapiens and Homo sapiens neanderthalensis? A closely related issue is: Could the two stocks cross-mate, producing fertile offspring?

Apparently they could, and did. That’s what we learned this month. A team of biologists in Germany has for several years been working to figure out from fragments of bone what the DNA of Neanderthals looked like. We already know what modern Homo sap. DNA looks like. (There’s a specimen here.) The researchers now have enough Neanderthal DNA to be able to declare that yes, there was successful cross-mating. The base populations of Homo sap. outside Africa have genomes with 1 to 4 percent of Neanderthal genes.

These are early results, and there are problems to be resolved. So far the archeological timeline seems not to match the genetic timeline (which can be estimated from known rates of genetic change). We also don’t know much about what, if anything, the Neanderthal genes do. “Some of the genes seem to be involved in cognitive function and others in bone structure,” says the New York Times report vaguely. And of course we know nothing about the intimate encounters that must have occurred to produce the gene-mixing, whether they were peaceable or violent. We only know they occurred, between creatures not much different from ourselves, in the unimaginably remote past.