I’m 2.7% ‘Neanderthal’: The language of evolution

According to a recent analysis of my DNA done by this company (which was a company used by Henry Louis Gates Jr.’s series “Finding Your Roots” on the PBS), 2.7 of my genetic material comes from Neanderthals.

dna

Not that this amount of Neanderthal makes me unique — I’m only at the 41st percentile. But it was only recently that it humans were understood to have any Neanderthal ancestry at all. But knowing this about myself, I watch shows about Neanderthals, like this one I watched last night, in a different way than I used to. They’re my people — well, are Neanderthals people? I guess it depends how we define people.

Definitions like this matter a lot when we start talking about genetics and evolution, as “Your Inner Fish” does (also, here). Watching episode 2 — “Your Inner Reptile” — last night, I was struck by how easy it is, when talking about evolution, to make it seem like evolution is an active force that guides/aims the change in organisms toward the end of becoming what they have become, rather than thinking of evolution as a passive descriptor of an essentially random process that it technically is.

I’m not a biologist (and if I’m getting this wrong, I’d appreciate hearing from an evolutionary expert), but my understanding of evolution is that the act that causes alterations to the bodies of a certain line of creatures over generations is genetic change in new offspring. Due to sexual recombination of genes, as well as random mutations that occur, individual creatures are born with features that may be different than what any parent has. For a crude example, perhaps a baby squirrel is born with four eyes. And, while many new features are useless or even harmful to the individual creature, perhaps having four eyes helps that creature survive and reproduce more than its fellow squirrels. Eventually, four-eyed squirrels could be so much more successful at living and reproducing than normal two-eyed squirrels that eventually all of the squirrels that get born and survive are four-eyed squirrels.

Now, of course, none of the two-eyed squirrels became four-eyed squirrels. No squirrel born without four eyes would spontaneously start to grow four eyes. A squirrel is born with the genes it gets, and even if some person decided to give that squirrel two additional eyes via surgical implantation, that squirrel would not have the genes to create children with four eyes. (Of course, there could be genetic engineering to do such a thing, and some bacteria just share their genes).

And so lately I’ve been thinking that what we label as “evolution” is an abstraction used to describe the perception of physical changes in successive generations of offspring. This is associated with the idea that each person alive now (assuming no human has yet been made in a lab from one parent’s doubled genes) must have had ancestors going back to, well, when life first started. I am here because my parents created me, and their parents created them, and so on, back to the first molecules that could replicate themselves. So I come from a genetic line of individuals who were successful at reproducing themselves going back to early humans, to proto-humans, to proto-mammals, to creatures who looked more like reptiles, to creatures who looked more like fish, to single-celled organisms.

And the change between any two generations, children compared to parent, was likely quite small — the big changes, like from one species of proto-human to Homo sapiens, can be seen only by comparing individuals who are millions of years (and many, many generations) apart.

But of course, to label different creatures as being of differing species is to draw distinctions that are perhaps useful but certainly arbitrary. (Yes, a species is defined here as “the largest group of organisms capable of interbreeding and producing fertile offspring,” but of course, this boundary is apparent only many, many generations after the original divergence).  Any two individual organisms that are compared will have some things in common but not other things. The term “evolution” then is applied to explain these differences in individuals where one individual may be an ancestor of the other, but “evolution” is not itself a physical entity. Physical organs are touchable things, as are offspring, but “evolution” is an abstraction.

2 responses to “I’m 2.7% ‘Neanderthal’: The language of evolution

  1. My mother-in-law also has Neanderthal DNA (I don’t know the %). It’s interesting how learning more about our ancestry can change how we relate to others. I don’t really know why ancestry matters (beyond understanding genetic predisposition– for which 23andMe has gotten into trouble)–it just does.

    • Your point about why this matters is an important one, and I’m not sure I’ve even fully explained to myself yet why this matters. Most of my DNA results vis-a-vis ancestry were not surprising — they more or less matched what I expected, from what I knew of my ancestors — but the percentages were off in mildly surprising ways. But my wife’s DNA analysis showed a little more mixing than we were aware of. My first reaction, I think, to finding ancestry that wasn’t expected is the feeling that I am, and my wife is, less narrowly defined than we had believed ourselves to be. I feel a bit more interest now in cultures beyond the ones of my most-direct ancestors. I also get a sense of nationality mattering much less, being less definitive, than I had thought.

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