Missing Links in Understanding

The other day a co-worker and I were messing around with Mac OS X. An opportunity for a pun came along, and I jumped at it. It was about Darwin (the name of the Unix core that OS X is built on) and some directory links that hadn't been copied yet; I called them "Darwin's missing links".

The coworker then went off on a tangent about how evolution makes no sense. "Why are apes still apes?" he challenged. "Why aren't there any half-evolved animals anywhere?" he demanded. My mind was occupied by operating system arcana and my strained attempts at social banter, so I mostly just stammered and tried to turn the subject back to our shared interest in Apple's computers.

I don't know this guy well, but he's never shown any evidence of being a fundamentalist religious nutcase who can't stand the fact that "God" isn't mentioned anywhere in most discussions of evolution theory. And it dawned on me later that his main problem was just that he simply didn't understand what he was talking about. Evolution makes no sense to him, because he's missed the whole point of what "natural selection" is and how it works.

Rather than re-opening a touchy subject with a co-worker (and risk actually bringing religion into it, at which point I'll undoubtedly say things I'll regret), I'm going to do it here.

The key point that many people seem to miss is that evolution is not some inexorable process of change, with some kind of destination in mind. It tends to look that way from where we sit, looking at those "ascent of man" posters, especially when overlaid with a veneer of "man is the pinacle of creation" egocentrism. Popular entertainment like the X-Men perpetuate this misconception by suggesting that mutants are "the next step in human evolution"... as if that next step were pre-ordained.

It's not. If the environment that humans live in were to stay the same for the next hundred millennia, there would be no next step in evolution. It wouldn't be needed. Humans are already pretty well adapted to our environment, so there'd be no particular survival advantage in them changing. Alligators and sharks, for example, have existed in pretty much their current form for ages (literally), because their basic environment hasn't changed much. They didn't need to adapt, so they didn't.

Our distant ancestors were a different story. Whether it's because their environment changed and they had to adapt to survive in it, or because some random variations made it possible for them to move to a different environment, they evolved to fit in that environment. The ones that didn't, died. That's what natural selection is all about: survival of the fittest.

Note that "fittest" doesn't mean "best". It's not an absolute that says "smarter is better" or "stronger is better". It all depends on the context. The dinosaurs flourished because they were "fittest" for living in the prevailing habitats. Brains weren't that important, but size apparently offered some advantages. Ergo, a lot of stupid, big dinos were among the "fittest". Then they died off, because there weren't "fit" to live through the climate changes following a big meteor strike, and especially not through the later Ice Age. Some reptiles were, and they survived. A lot of mammals were, and they thrived.

So to answer my coworker's question: apes are still ape-like (rather than becoming human-like) because being an ape has been a great way to survive in the jungles of Africa.

The whole concept of being "half-evolved" is jibberish. If something isn't properly adapted to its evironment, it's unfit. It doesn't survive. So every living species is, by definition, "fully evolved"... for their current environment. I assume he was wondering why there aren't any species halfway between homo sapiens and homo habilis. That's kind of like asking why nobody lives halfway between Grand Rapids and Milwaukee; sure Milwaukeans are suited to living in Wisconsin, and Grand Rapidians are suited to live in Michigan, but nobody's very well suited to living at the bottom of a huge lake.

Likewise, there's no environment left on earth for which homo erectus (a decendent of habilis, and ancestor of sapiens) is better suited than we are. The ancestors of apes stuck to the trees and continued to dominate that niche. They got bigger, and somewhat smarter (modern chimps have bigger brains than the earliest hominids), but they didn't change as dramatically as humans because they didn't need to. Meanwhile, the ancestors of humans apparently moved on to riverbanks, seashores, and dominated those areas. As they adapted better to live on the ground and walking upright, they took over more parts of the world, until they got where we are now.

Evolution theory doesn't explain all of the evidence we've uncovered, and there's some that even contradicts it. But if you know what the theory actually proposes, and understand what "natural selection" and "survival of the fittest" are really about, objections like my coworker's fall apart. He's not arguing against evolution, but against an uninformed parody of evolution. Which is all the more reason it needs to be taught in schools: so an intelligent, reasonable person such as he can reach an informed conclusion whether it's sound or not.