Jim Holt writes in the New York Times magazine that nothing about the design of living things on earth appears to have been designed intelligently:
From a scientific perspective, one of the most frustrating things about intelligent design is that (unlike Darwinism) it is virtually impossible to test. Old-fashioned biblical creationism at least risked making some hard factual claims -- that the earth was created before the sun, for example. Intelligent design, by contrast, leaves the purposes of the designer wholly mysterious. Presumably any pattern of data in the natural world is consistent with his/her/its existence.
But if we can't infer anything about the design from the designer, maybe we can go the other way. What can we tell about the designer from the design? While there is much that is marvelous in nature, there is also much that is flawed, sloppy and downright bizarre. Some nonfunctional oddities, like the peacock's tail or the human male's nipples, might be attributed to a sense of whimsy on the part of the designer. Others just seem grossly inefficient. In mammals, for instance, the recurrent laryngeal nerve does not go directly from the cranium to the larynx, the way any competent engineer would have arranged it. Instead, it extends down the neck to the chest, loops around a lung ligament and then runs back up the neck to the larynx. In a giraffe, that means a 20-foot length of nerve where 1 foot would have done. If this is evidence of design, it would seem to be of the unintelligent variety.