Robert Frost on Evolution

A bird half wakened in the lunar moon
Sang halfway through its little inborn tune.
Partly because it sang but once all night
And that from no especial bush's height,
Partly because it sang ventriloquist
And had the inspiration to desist
Almost before the prick of hostile ears,
It ventured less in peril than appears.
It could not have come down to us so far,
Through the interstices of things ajar,
On the long bead chain of repeated birth,
To be a bird while we are men on earth,
If singing out of sleep and dream that way
Had made it much more easily a prey.

The first evolutionary concept Frost uses here is "inborn." He sees the traits of the bird as innate, the product of a biological heritage. Then the speaker of the poem wonders why the bird (this species of bird) has survived, why it is fit for survival. Surely a bird singing in the middle of the night like that would be swooped up by an owl or other nocturnal hunter? So he devises an evolutionary explanation of sorts. First of all, he makes a few excuses. It only sang once, and not for very long. Secondly, he makes an almost tautological argument: if the bird did in fact survive, then singing at night once in a while could not have been too maladaptive. After all, the bird is still there! The argument is not strong, because maybe this particular bird was eaten by an owl the minute after the speaker heard the song. Individuals with maladaptive traits exist, even the the species itself has adapted to a particular habitat.

Evolutionary Change

Now that we've established common descent we have admitted the principle of change. The ancestor of the dog and horse had to change, somehow, into a dog and horse. Common descent implies that species are not locked in to a single pattern throughout the biological time-line.

The next thing that is fairly intuitive is that change has happened. Modern mammals didn't exist during the vast swaths of time when there were dinosaurs. It is obvious that there has been change (i.e. evolution) because of the fossil record itself. Species are born and die just like individuals.

But how does it happen? First of all, descent implies generations, the "long bead chain of repeated birth," in the words of Robert Frost. If individuals just stayed around forever and never reproduced, you couldn't have change. Secondly, you need a certain variability within a single generation, a single population. If every individual were the genetic clone of every other one, you wouldn't have much to work with. What's not intuitive here to the layman is how this mutability can produce such wide variation. Even creationists admit biological variability and small changes, after all. They know that dog breeders have produced breeds of dogs with traits different from other dogs. They just won't accept larger changes. They still believe that species are essentially locked into an immutable pattern. They can't accept that a dog and a wolf are related, or a wolf and a sabre-tooth tiger, and so on up the chain. They will tell you, sure, micro-evoluation exists, but not macro.

But once you get someone to admit a wolf is related to a dog, once you admit that species arose or became extinct, then it's hard to draw a line saying that biological change has a fixed barrier at the level of species. It would be like saying Spanish can change, can have dialects and regional differentiations, but it will never actually change into a completely different language.

The next logical step might be to look at mechanisms of change: selection, adaptation, and the so-called "survival of the fittest."

(Once again, I'm trying to reason all this out just with my extremely limited knowledge. I think people confuse themselves by knowing too much and ignore the intuitive simplicity of some of this. Also, though, I'm trying to understand why evolution is counterintuitive to people who don't readily accept it.)

Common Descent

The easiest concept in evolution to grasp is common descent. If you take a bunch of varieties of oak trees, you can figure out that there was a common ancestor to all these varieties. And of all trees further back. You can see that a cat is related to a tiger and a lion. There is a kinship there. You can also see lesser degrees of relation among more distantly related creatures, birds and mammals, say. So the classification of animals and plants into hierarchical categories already implies this relatedness. To me this is more intuitive than other concepts in evolution, and more self-evident. We see a similar kind of branching effect in language. Italian and Spanish obviously are different languages but they share a common ancestor. Or styles of rock music. It is obvious that they evolved from common roots, that they bear similarities and relationships through common origins rather than from some individual act of creating various styles all at the same time. Biological life, too, looks more like a thing that developed through a series of changes like that, than like something designed consciously all at once. Evolution had to be invented, by Darwin or someone else, once there was enough knowledge of biology, simply because of the intuitive principle of kinship. You can tell one kind of cow is related to another variety of cow, but less related to a horse. Not even the stupidest creationists try to go against common descent overtly, because it is just too powerful.

Once you admit common descent, though, isn't the rest of evolution just inevitable? All you need after that is a mechanism of change and differentiation, mutability and selection, and a long enough time-scale for it to occur. I'd like to reason this out for myself in entirely layman's terms, since i'm not a scientist of any sort. I actually think it's more important that I understand it than for someone who already knows this kind of thing professionally. A shocking number of Americans don't accept evolution at all, so in this case a simplistic understanding is better than a sophisticated one.

Bullshit Fields

One bullshit field is so-called "evolutionary psychology." What this field does is to take a given human trait and explain how it was an adaptive trait in the primeval human habitat where humans first evolved, through speculative "just so" stories. Now I believe that human evolved, and that, generally speaking, all the traits we have are (tautologically speaking) adaptive. So the stories are largely pointless. We gossip, say, and we evolved to gossip, because we needed during some earlier stage of prehistory, to figure out what was going on in our small group of hunter-gatherers, so someone wouldn't clobber us on the head with a rock. (I actually heard someone make this argument on NPR a few days ago. I kid you not.)

When it is not merely tautological, evopsych is ideologically obnoxious, since it is always some negative trait that is supposed to adaptive. But if we evolved to do everything we do, why do they only make arguments for the evolutionary advantages of certain traits and not others? Sociobiology is always obnoxious in exactly this way, making the specious argument that you cannot fight against human nature.