Evolution News finds the problem with the evolution of mimicry

The Discovery Institute’s Evolution News website is the foremost site for advocacy of Intelligent Design. We should therefore expect its arguments to be technically sound and convincing. An extraordinary example of their standards appeared recently there. On the 23rd of July, Denyse O’Leary, who posts there often, explained why: For Darwinism, Here Is the Problem with Butterfly Mimicry.

She starts by noting a scientific paper which examined the evolution of a type of mimicry in which what look like large eyespots occur near the rear end of butterfly wings. A similar example in butterflyfish will be seen in the image above. These false eyespots might tempt a predator to attack that end of the butterfly rather than its actual head. The paper examines such color patterns across many butterfly species, and finds that the elements of the pattern evolve together in different parts of the evolutionary tree, multiple times.

The authors of that paper conclude that this repeated correlated evolution is most likely the result of natural selection for mimicry. Not so Denyse O’Leary. She sees a big problem: the fallacy of “the five percent solution”. If the pattern is only five percent present, how can it be favored by natural selection?

Charles Darwin (uncredited by O’Leary) gave a convincing argument for how eyes in animals could evolve, starting with a mere light-sensitive spot. O’Leary argues that no such argument can be made for the false eyespots:

I call this the “five percent solution” because of a question asked in the article at PBS above, “What good is five percent of an eye?” And a reasonable answer is: Some good. Even a light-sensitive spot is better than no vision at all.

But Now What about the Five Percent Problem?

The dead leaf butterfly’s challenge — to take one example — is quite different from the one a blind worm faces. The blind worm is better off with five percent of visual information, as opposed to none at all.

But a method of deception that is only five percent persuasive is not a first step on a road to a solution. Looking only five per cent like a dead leaf would likely prove fatal to the insect that relied on it. The false head butterfly would face the same problem: If the wing spots looked only a bit like a head for aeons, the gradually evolving insect would need a different method of self-protection for quite a long time. And, under the circumstances, why would either the dead leaf or false head mimicry continue to evolve? There really isn’t an adequate answer to this problem because Darwinian evolution is not thought to show foresight. The usual response has been to Cancel the question instead. That submerges the question but doesn’t make it go away.”

I’m not convinced. O’Leary assumes an all-or-nothing view of adaptation. Either a species is fully adapted, so that the mimicry is fully effective, or it has no adaptation at all. But encounters between predators and prey occur in many different circumstances, sometimes with predators having a good view of the potential prey for a long time, and sometimes with them having only a brief and obscured glimpse for just a moment.

A prey individual may be covered with irregular blotches, as a means of cryptic coloration. And these blotches may occasional strike the predator as eyes. If that can cause the predator to misdirect its attack, this pattern may have a small increase in fitness. The resulting small selection pressure can gradually make the pattern of blotches more like a pair of eyes. (I should add another possibility – that the false eyes make the prey look like the head of a larger species, such as a snake. That would tend to deter the predator from attacking.)

Invoking the 5% problem and assuming that only a 100% mimicry can have any effect on fitness follows a common argument of opponents of natural selection. Both of the two main ID arguments, complex specified information and irreducible complexity, seek to do away with the possibility that effective adaptations could arise step by step.

The common thread in all this is that advocates of ID and/or creationism simply don’t understand how natural selection works in populations. Any noise, uncertainty, or weakness of selection pressure is assumed to prevent adaptation from being achieved at all.

Denyse O’Leary’s argument, like most others she makes, reveal a thorough misunderstanding of evolutionary biology. They end up being astonishingly weak arguments. They reveal that the DI, in Evolution News, is willing to endorse absurd arguments as meeting its supposedly-high standards.