No three words are more pregnant with the promise of error in a conversation with a creationist than to hear them say “what evolution predicts…”. It’s practically a guarantee that you’re going to hear something bizarre and fundamentally erroneous — but it is at least a good start on identifying basic misconceptions. Orac has found a doozy, a creationist who goes on at remarkable length, building a house of cards on a few flimsy premises. He’s dealt with it thoroughly, so I just want to focus on one piece of Pat Sullivan’s deeply flawed understanding of evolution.
Imagine an area of town where a major real estate development is taking place. Over the course of the development, on any given day one would observe “incompleteness.” But there would come a time when it basically would be complete. Some stores will go out of business and a different store takes it’s place, but no big changes as a whole. If random macro evolution is responsible for what we see, why would it not be like a massive development where things NEVER appear finished or complete? What brought macro evolution to a halt? Could it be that it simply never happened?
To me this makes the “Cambrian Explosion” all that more troublesome for evolutionists. This refers to the fact that in the fossil record entire species suddenly appear totally complete. No transitional forms at all. This in total contradiction to what the theory of macro evolution seems would have predicted.
This is the crux of his argument against evolution: that he never sees any organisms that he recognizes as “incomplete”. His example is that he doesn’t see any three-legged cows with a fourth in the process of evolving.
You read that right. No three-legged cows, no evolution.
There is so much that is wrong with that whole argument. Here’s a partial list.
The immediate ancestor of the cow was four-legged. The last common ancestor of all mammals was four-legged. The last common ancestor of all tetrapods was four-legged. We have to go back several hundred million years to find a cow ancestor that was not four-legged, but we’ve got them. Of course, it was four-finned, not three-legged.
Evolution does not proceed by selecting for organisms that are partially constructed steps on the way to some future “complete” organism. Every transitional form must be fully functional; that’s what is predicted by evolution, and that’s what we see. The distant ancestor of the cow was a healthy, thriving population of fish-like forms with paddle-like fins. The fins were modified by evolutionary processes for hundreds of millions of years, but every intermediate step was viable and useful for locomotion. We see forms like this:
Which one is supposed to be “incomplete”? Yet we can clearly see a pattern of change in this lineage from fish-like fins to amphibian limbs.
Biology doesn’t work the way creationists imagine it does: there isn’t some blueprint in the genome with a spot where the right hindlimb is sketched in. It’s all much more abstract, with a general to specific array of tissue specification that is dependent on interactions between cells and their environment. What we have in development is, for instance, an early establishment of bilateral symmetry, so that an operation that occurs on one side of the embryo will be mirrored on the other. It actually takes special additional mechanisms to break that symmetry; pairs of limbs are the default. This symmetry was established well over half a billion years ago, and we see its maintenance in modern organisms.
Similarly, the metazoan lineage established a pattern of positional information along the axis using Hox genes, and within the vertebrate lineage some animals established anchors for serially repeated limb development, setting up fore- and hind-limbs. That pattern is also very hard to break; we have inherited a constraint that commits us to a tetrapod body plan.
Sullivan’s line of argument here is a familiar one. It’s the same as Pinkoski’s, which compounded his misconceptions about symmetry with the bizarre idea that evolutionary changes were an act of will.
The notion that evolution can ever be “complete” is false. Evolution is not about progress towards some goal, but about near-constant change to circumstance. It doesn’t stop, and it hasn’t — we’re still changing, slowly. Are we now incomplete because future generations will differ from us?
The Cambrian Explosion is not troublesome, it is interesting. It suggests some concordance in the evolution of disparate lineages; within a broad span of time (millions of years), we see many metazoan forms expanding in size and developing harder and more easily fossilized body parts. There are plenty of transitional forms here, and what’s interesting is that many disparate phyla are changing in similar ways at roughly the same time, which suggests that there are coordinating macroevolutionary processes at work.
But let’s not forget something else that’s important: the Cambrian Explosion seems to be a phenomenon of most importance to one group of organisms, the animals. One narrow group of organisms diversified at this time, but others, like the bacteria and plants and fungi, were doing their own thing. The fascination with the Cambrian is in part a selfish interest in our personal history.
See what I mean? The creationist has his own weird little fantasy version of what evolution predicts, and he has made what is actually to his mind a logical conclusion: that because the real world doesn’t look anything like what his version of evolution predicts, scientist’s version of evolution (which, of course, is nothing like his) must be wrong.
The hard part in addressing that complaint is that it requires going in and systematically dismantling his freakishly false version of evolution first, and then trying to build up a more accurate model in his head. It takes education — the kind of education poor Mr Sullivan should have been given in grade school, before his ideas calcified into this strange nonsense.