Chalk up another setback for the intelligent design (ID) crowd. In a lengthy treatment of unfortunate sexual traits in Science News, writer Susan Milius explores the counterintuitive notion that evolution can sometimes produce characteristics that are, well, no good. The examples cited range from bemusing to downright gross: seed beetle genitalia that grievously injure females during the mating act, sexual apparatuses in ducks that are remarkably incompatible between males and females, and costly peacock tails that—contrary to decades of speculation about their role in mating advertisement—actually seem to do nothing to attract females.
Researchers have known for a long time that sexual selection sometimes produces traits that, from a purely practical standpoint, seem less than advantageous. The classic example is the enormous rack of antlers grown by elk, which require a lot of energy to produce and don’t help with—and in fact often hinder—basic survival activities like foraging for food. Scientists postulate that the reason for the antlers is not only to compete physically for females’ attention, but also to advertise the males’ fitness. If a male elk can afford to spend the energy to grow antlers and still survive the winter, he’s probably a good specimen. The advertisement hypothesis has also been applied to peacock tails and other outlandish traits.
However, a startling recent study done with feral peacocks in Japan and cited in Animal Behavior (and in Milius’s article) hinted that such conspicuous energy consumption isn’t always a winning strategy. After seven years of observing peacocks near the city of Shizuoka, the study’s authors determined that the peahens weren’t particularly impressed by the males’ tail plumage, the peacock equivalent of costly, impractical antlers. Peahens mated with long-tailed and short-tailed males without apparent regard to the number of blue spots or extensiveness of the feathers. The researchers were left asking themselves what purpose those energy-intensive feathers served if they weren’t effective in attracting mates.
The answer may be more absurd than scientists typically feel comfortable with. Milius and the scientists she cites suggest that some sexual characteristics can evolve essentially at random, spurred on by a delicate combination of environmental and social factors, by plain inertia, or even by “arms races”—the reciprocal development of defensive and offensive tools for getting one’s way in the mating game.
Seed beetles are a potential example of the latter; as males initially developed sex organs that caused a small amount of harm as a side effect, researchers suggest, females evolved to have more protective tissue guarding their own genitalia. This then prompted males to develop even more aggressive-looking equipment, and voila – today, seed beetle mating is closer to being a death match than a loving embrace, and some specialists in the field don’t hesitate to say that this is actually bad for the entire species.
The potential implications of negative evolutionary developments for the religiously minded are numerous. The fact that creaturely design is not only imperfect but sometimes outright harmful may throw another wrench in the machinery of the beleaguered Intelligent Design movement. How can people speak realistically about an intelligent designer, we might ask, if the design itself just isn’t that intelligent? The image of an entire species of beetles slowly dying off because they cause lethal harm to one another during mating is more than a bit incongruous with ID’s conception of a highly balanced, well-ordered universe.
In fact, the existence of harmful traits is possibly among the best arguments for evolution driven by natural selection. The random development of characteristics that may eventually lead to the extinction of the species seems far more compatible with purposelessness than with a divine order. On the other hand, God isn’t necessarily eliminated from the picture, either. If no adaptive reason were to be found for peacock plumage, for example, some people might take it as evidence that God—or Nature—simply has an innate whimsy to it, not to mention a predilection for beauty. In fact, in light of the facts presented in Milius’s article, that might be about as reasonable an explanation as any.
Read the original article here.