The smell of love, part one

Why do some people smell better to you? A look at how human body odor influences sexual attraction.

After long dismissing the search for a human pheromone as folly, scientists have begun to take a second look at how human body odor influences sexual attraction. The magic scent is not some romantic elixir but the aromatic effluence of our immune system. The only trouble is we don't give it half a chance.

How do we humans announce, and excite, sexual availability? Many animals do it with their own biochemical bouquets known as pheromones. "Why do bulls and horses turn up their nostrils when excited by love?" Darwin pondered deep in one of his unpublished notebooks. He came to believe that natural selection designed animals to produce two, and only two, types of odors -- defensive ones, like the skunk's, and scents for territorial marking and mate attracting, like that exuded by the male musk deer and bottled by perfumers everywhere. The evaluative sniffing that mammals engage in during courtship were clues that scent is the chemical equivalent of the peacock's plumage or the nightingale's song -- finery with which to attract mates.

In the following century, a rich array of animal pheromones were documented for seals, boars, rodents, and all manner of other critters. But not for human beings.

Some of Darwin's contemporaries embraced human uniqueness in this regard as evidence of our inevitable ascendance, as if Nature's Plan somehow called for the evolution of a nearly naked two-legged primate with a poor sense of smell to conquer the Earth. The French physician Paul Broca -- noting that primates' social olfactory abilities are diminished compared to those of other mammals -- asserted that monkeys, apes, and humans represent ascending steps from four-legged sniffing beasts to sight-oriented bipeds.

Monkeys, he argued, have smaller "smell brains" than other mammals, and apes' brains are even smaller than that. Among humans, only the tribal "primitives," Broca wrote, could still attach erotic import to the bodily smells of man.

More enlightened researchers dismissed such views as racist tripe. But they still noted that humans engage in very little scent-driven socializing -- compared to, say, the urine-washing displays of monkeys (during which urine is rubbed on the feet to attract mates).

To make matters worse, humans seemed to lack the hardware for communicating by scent. Pheromone reception in other species is the business of two little pits (one in each nostril) known collectively as the vomeronasal organ (VNO). Few scientists of the time claimed to have been able to locate a human VNO. Those who did complained that the VNO is so small that they could detect it only rarely.

But most scientists, without bothering to look, simply dismissed the idea of a VNO in humans. It's been scientific dogma for most of this century that humans do not rely on scent to any appreciable degree, and that any VNOs found are vestigial throwbacks. Then, in the 1930s, physiologists declared that humans lack the brain part to process VNO signals, firmly closing the book on any role for body odor in human sexual attraction. Even if we had a VNO, the thinking was, our brains wouldn't be able to interpret its signals.

Recent discoveries suggest, however, that the reports of our olfactory devolution have been greatly exaggerated.

Some suspected as much the whole time. Smell researchers Barbara Sommerville and David Gee of the University of Leeds in England observed that smelling one another's hands or faces is a nearly universal human greeting. The Eskimo kiss is not just a rubbing of noses but a mutual sniffing. "Only in the Western world," the researchers point out, "has it become modified to a kiss." Hands and faces may be significant choices for these formalities -- they are the two most accessible concentrations of scent glands on the human body besides the ears.