|
|
Creationism is mistaken:
(i) A number of plants are heliotropic: they turn to face the sun, and their leaves curl up at night. Clearly, having photosensitive cells, even without a central nervous system, can be beneficial. (ii) Some fish have retinas but no lenses. They need to react quickly to passing shadows -- which may signify predators -- without distinguishing among the kinds of shadow, which anyhow might be too difficult to do in the murkiness of the sea. (iii) Dogs reputedly have only rod cells, for black and white vision, while primates have cone cells too, for color. Conversely, primates cannot see ultraviolet, whereas bees can. (iv) Some species have nictating membranes for protecting the rest of the eye. By this means, for example, camels can see in a sandstorm where humans cannot. (v) Higher life forms tend to have nerves reaching from their exterior boundary (the skin) to the brain. If, for some reason, one patch of the exterior boundary were to become photosensitive, it would hardly be surprising if the pre-existing nerves were to be co-opted for sending visual information instead of tactile information.
In general, it makes perfect sense to regard many of the components of the visual system as possessing independent functional value. (Lenses probably have no independent value. But if you suppose that the retina developed first, and that it was covered by a translucent layer of cells for protection, you can easily imagine why those cells might evolve into a convexity that focused light.) Contrary to thinking that the evolution of the eye is hard to understand, biologists have identified some forty evolutionarily distinct pathways for vision!
Creationism is irresponsible:
Argumentation does not involve just logic (premises, inferences, and conclusions, all considered abstractly, i.e. as standing outside of time). It involves dialectic (parties taking turns, responding to each other's points, an ever shifting burden of proof). Let's rehearse the current dialectic. First the creationists said that the only explanation for life, or at least the best explanation, is the divine creation theory, and on this account they developed an extensive body of literature (so far, so good). Second, Darwinians, steeped in theistic literature, replied that the principle of natural selection gives an explanation that is as good or better, and now they too have put forth a great deal of literature (so far, so good). Third, current creationists maintain that natural selection cannot explain the eye (and not just an eccentric handful do, but quite a few). Now current creationists, unlike those who lived in the Middle Ages, are supposed to respond to the Darwinians. It is their duty, if they are to engage in debate, to engage! If they want to assert that Darwinians cannot account for the eye, they need to find out what Darwinians say about the eye, and address it. (This should be fairly easy to do, for every university library contains the relevant journals, and these journals are indexed.)
My requirements are not harsh. I'm not saying that creationists, in order to be qualified critics, must spend all their time in the library, or train as professional biologists, or understand Darwinian theory as well as Darwinians do. Rather, I would like to suggest the following very modest standards. First, if you are going to publish a refutation of Darwinian theory, you should know at least as much as I do about it. If I, a complete amateur at biology, can see that the eye objection is unsound, then authorial creationists (those who write for publication, those who represent themselves as authorities) should be able to as well. Second, many of the facts enumerated above (i-v) are well known or obvious. Since they are widely accessible, even uneducated creationists ought to take them into account. (Indeed, some of the "facts" are too well known: dogs are not really colorblind, although plenty of other animals are.) Because the eye objection ignores these common-sense facts, it is not only mistaken but inexcusably so. [I want to be wary about raising any ad hominem argument, but I also want to voice my concern that creationist arguments often strike me as intellectually dishonest.]