Everyone is familiar with the smell of a sweaty male. What's interesting to some scientists, though, is how different people perceive that smell. For some, the scent of male sweat is unpleasant. Others find it more pleasant and can even describe the aroma as sweet, or smelling like vanilla. Now Duke University researcher Hiroaki Matsunami says that what determines the difference in perception might lie in our genes.

Matsunami and colleagues from the Rockefeller University found that some people reacted strongly to two chemicals found in men's sweat – androstenone and androstadienone. "These are steroid chemicals, and these chemicals are breakdown products of the male hormone testosterone, explains Matsunami. "And the chemicals are volatile, so people can smell them, but for some reason, about 30 percent of the population cannot smell these chemicals."

Matsunami's colleagues presented about 400 people with a range of scents and asked them to describe and rate the smells as pleasant or distasteful. They also took blood samples from all the subjects. Matsunami examined their DNA, looking at genes that controlled the ability to detect these odors. He says there are a number of theories other than genes that may determine how people detect any kind of chemicals. "Cultural background, or experience, may play a very important role in how you smell chemicals or odors. We did indeed find a very strong link between differences in genes and the perception in humans."

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Matsunami suggests both androstenone and androstadienone may act as a perfume to attract the opposite sex since it's that way in some other mammals. "It's been proposed that these chemicals may act as a signal of 'maleness,'" Matsunami says. "So if you produce more testosterone, you produce more androstenone, therefore females can evaluate a mate. So that's a theory that may or may not be true in the modern human society." Matsunami's research revealed for the first time the extreme variations in the particular gene that determines how people perceive the smell of these chemicals. His research is published in the journal Nature. (VOA/JC)