Everyday Mysteries
WHY DO DOGS BARK? Dogs can be pretty good communicators. A yelp is easy to recognize as a sound of distress. Growls are obvious. A whine, coupled with a scratch at the door, may just keep the carpet clean and dry.
But what about barking? Is a dog sounding an alarm? Defining its territory? Just playing? The principles of evolution dictate that animals retain traits through natural selection. They hang on to functions that contribute to their survival, and that applies to making sounds no less than anything else. Scientists believe male birds sing, for example, to mark their territory, to attract mates, to maintain pair relationships, and to warn of impending predatory doom. But barking seems to defy all the rules of biological necessity. Biologists Raymond Coppinger and Mark Feinstein, who have studied this puzzle, say dogs often seem to bark extravagantly and for no apparent reason at all. The two Hampshire College scientists once spent the night in a Minnesota field listening to a guard dog bark continuously for seven hours. There were no other dogs around, no humans responding, no predators lurking. It just barked. Feinstein recently came upon two dogs in a hot car. "One was barking like crazy, the other staring out the window. They were under the same conditions," he says. "They've got this capacity which doesn't play any necessary function in their lives."
Those dogs, like all domestic dogs, are descended from the wolf, and wolves don't bark much. But their puppies do, and Coppinger and Feinstein believe that may help explain the mystery of barking. Early dogs (wolves really) were scavengers, hanging around human habitations--and their plentiful heaps of garbage. Humans, in turn, tended to tolerate the tamer ones; it was they that became the sires of what would become the domestic dog. Experiments in a number of animals have shown that breeding for tameness breeds animals that are, in effect, perpetual adolescents, displaying many youthful traits into adulthood. "You get an animal more like a juvenile wolf," says Feinstein.
So why do juveniles bark? Feinstein and Coppinger believe wolf pups are in a transition period; a bark is acoustically half-way between an infantile attention-seeking whine and an adult, hostile growl.
Adult dogs do find ways to use their barks to communicate; they might be asking to go in or out, defending territory, or just playing. But as Feinstein notes, precisely because barking has no biological necessity for dogs, "they can adapt it to use under almost any circumstance."
Ultimately, science's best answer may be the punch line of the old joke about why dogs chase their tails and lick themselves: because they can.
WHY DO PEOPLE LIKE HOT PEPPERS? Lovers of fiery cuisine and scientists alike agree that the hottest chili pepper is the habanero. Waxy and thumb-size, the habanero produces a punishing punch many times more intense than the better-known jalapeno. Chili pepper flavor is as complex as good wine, says Paul Bosland, a New Mexico State University professor. The habanero, he says, has a unique flavor and a "back-of-the-mouth, top-of-the-throat kind of heat. It's a persistent heat." Bosland, who is also director of the Chile Pepper Institute, says chili eaters work up to a "habituation level."
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