Tuesday, March 11, 2008
[L]et's look at one of the more common "knock-down arguments" [creationists] use against evolution:
If humans evolved from monkeys, why are there still monkeys?Laugh if you want, but it is evidence of a deep confusion about evolutionary theory. Why indeed are there still monkeys? Why would someone think that there would not be monkeys if humans evolved from them? Now not all creationists think this is a good argument, but even so, why does it have some immediate effect on people?
The answer is simple – people think that evolution is a progressive process. Similar errors are involved in the claims that humans are the end of evolution, or that if humans went extinct, some other species would evolve to take our place as intelligent and civilised creatures. Let's look at the errors involved. There are four:
1. That evolution moves from simple and primitive to complex and sophisticated,
2. That intelligence is somehow the goal, the most sophisticated thing, a living organism can evolve towards,
3. That when evolution occurs, the entire species changes, and
4. That if evolution were true, we would see every intermediate form that ever lived.Each of these is not only wrong, it is in fact opposed to the scientific, Darwinian, view of evolution. The first is known by historians of ideas as the Great Chain of Being. It is an idea that goes back to the ancient Greeks, and which was especially active in the Middle Ages. John Waller, who is talking after me, will talk more about this, but it's enough to say now that according to this pre-Darwin view, change only goes one way, while for Darwin and all who have studied biology since him, it is sometimes more useful to an organism to get simpler than to get more complex.
The second encompasses a whole range of mistakes that are usually called "teleology", which is a fancy Greek term for "goal-centeredness". The idea here is that there is a goal towards which things evolved, and which made them evolve. This idea is something you will find often in science fiction, particularly in the Star Trek franchise. But evolution has no goal. It does not "look ahead" and "choose" what will happen – what happens happens first, and if it works better than before, or if it is no worse than before, it might get kept. Even more important is that if it changes or stays the same, it might still become extinct.
The third is a very basic mistake, and it's one that even famous evolutionary biologists have made, although not for a long time now. It is the idea that whole species evolve together. This means that if evolution happens, the critics think, then the older forms should disappear, but we see them (those monkeys, remember?) so therefore evolution didn't happen. In fact, modern evolutionary biology believes (and has observed) that evolution into new species happens only in populations. In short, the ancestor of a new species isn't an old species, but a population, or part only, of the old species. There are several mechanisms and processes for this I won't bore you with, but if anyone is interested, I can recommend a wonderful recent book called Frogs, flies and dandelions.
So, why are there still monkeys? Because the last shared ancestor of ourselves and monkeys did not go extinct when they split off from us, either because the whole species turned our way or because theirs was somehow a lesser pathway to take. Monkeys and apes do just fine in survival and reproduction terms, and that is what counts in evolution. Evolution was not heading in our direction, it got there almost by accident. And if we stopped existing, there is no reason to think there'd be a Planet of the Apes afterwards. That is, other than the planet of the apes that now exists, for we are apes, biologically speaking. But if some animal did evolve to intelligence of a human kind, I like to think it would be those meerkats – social, almost bipedal, and living in the strong selective environment of Africa, where we evolved. On the other hand, if they had any brains, and any control over their own evolution, they'd probably do better to stay pretty much the way they are…
- John Wilkins, "Misunderstanding Evolution"
What John was arguing against is the notion that the process of evolution moves life from simple and primitive to complex and sophisticated. To most scientists at least, evolution itself is directionless, moving life only towards differential reproductive success. The fact that life necessarily began at or near the minimum level of complexity it needs to do life processes meant that available niches for better reproductive success existed in the direction of greater complexity, such as multicellularity. But the trend (so the argument goes) doesn't reside in the process of evolution, it is a property of the environment (including already existing life).
Not all scientists agree, however. Simon Conway-Morris, for one, thinks there is directionality in evolution.