A primate's fragrance speaks volumes.

Perhaps judging a man by his cologne is not as superficial as it seems. Researchers at Duke University, Durham, N.C., using sophisticated machinery to analyze hundreds of chemical components in a ring-tailed lemur's distinctive scent, have found that individual males not only are advertising their fitness for fatherhood, but a bit about their family tree as well.

"We now know that there's information about genetic quality and relatedness in scent," says Christine Drea, associate professor of biological anthropology and biology. The male's scent can reflect his mixture of genes, and to which animals he's most closely related. "It's an honest indicator of individual quality that both sexes can recognize."

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Lemurs, distant primate cousins of humans who split from the family tree before monkeys and apes parted ways, have a complex and elaborate scent language that, until recently, remained undiscovered by humans. Drea indicates it is a language that undoubtedly is richer than we can imagine. "All lemurs make use of scent. The diversity of glands is just amazing."

Ringtailed males have scent glands on their genitals, shoulders, and wrists, each of which produces different smells. Other lemur species also have glands on their head, chest, and hands. Add to these scents the signals that can be conveyed in feces and urine, and there is a lot of silent, cryptic communication going on in lemur society. Wearing a scent-based nametag declaring one's genetics probably is useful in avoiding aggression with closely related males. It also is quite likely to help prevent inbreeding by signaling family relationships to females.

The males have a gland and spike on each wrist that is used to scratch and mark saplings with highly aromatic scents. A pair of glands on the shoulders "like misplaced nipples" manufacture squalene, a scent molecule that works like glue to keep the more aromatic compounds in place longer. Males can be seen dabbing the wrist gland on the chest gland and then scratch-marking. The wrist glands also are central to the "stink fighting" of ringtails, in which they rub the glands along the length of their bushy tails, and then foist them into each others' face to express dominance.

Most importantly, the male has a scent gland on his scrotum that becomes critical to marking territory and advertising fitness during mating season. He does a handstand and rubs this gland directly onto a tree trunk to let any interested lemurs know who he is and what he is made of. Scent not only speaks volumes, it is expensive to make physiologically, Drea adds. When a lemur is ill or socially stressed, its scent changes dramatically. "If he loses his signals, it's quite likely it's because he's less genetically fit, and his sexual or social partners can know that."

Female ringtailed lemurs have just one scent gland in the genital area, but their scent is more complex than the males'. Via scent, females may advertise not only their fertility, but the presence of a pregnancy and how far along it is, Drea points out.