Originally published 13 July 1992
We begin life sniffing.
Recent research suggests that human sperms are guided on their long, dark journey up the fallopian tube to a waiting egg by a chemical attractant emitted by the egg. The sperm, it seems, is a nose with a propeller. Its payload is a packet of genes.
Newborn infants seem to be able to recognize their mothers by smell, and some mothers can identify their babies the same way.
And, of course, we have all heard about those experiments in which the odor of underarm sweat was used to induce synchrony among the cycles of menstruating women.
No one knows how many other ways odors influence human reproduction. Perfumers make a bundle on the reality — or the perception — that a sniff of the right stuff can hurry things along.
Certainly, for many species, the nose is the most important sex organ. It’s a dog-sniff-dog world out there. The birds do it, the bees do it, even the blossoms on the trees do it.
It’s called “Chemical Communication,” which is the title of a new book on the subject by chemist William Agosta, one of that wonderful series of books in the Scientific American Library (W.H. Freeman, 1992).
The book’s subtitle is “The Language of Pheromones.” A pheromone is a chemical compound used for communication between members of the same species. The words comes from the Greek “pherein” — to carry — and “hormon” — exciting. Molecules carrying excitement.
The nature cologne works
Nature, it seems, is one big perfumery, exuding alarms and allurements from every pore.
A male silkworm moth can detect a mate from a distance of more than a mile; he finds her by flying toward denser concentrations of the attractant. The female moth’s irresistible perfume is called bombykol, a molecule made out of 16 carbon atoms, 30 hydrogen atoms, and one oxygen atom. Put these 47 ordinary atoms together in a certain way and they make the heart (and wings) of a male moth flutter. It doesn’t take much of this powerful stuff to agitate a male moth; a German chemist named Butenandt required the glands of half-a-million female moths to get enough bombykol for analysis.
Perfume allurements can be dangerous because pheromones can be faked. A female bolas spider does not weave a web, but instead spins her silk into a sticky ball on the end of a thread that she swings like a bolas (those weighted ropes used by South American cowboys instead of lassos). Then, all night, she emits a chemical that mimics the sex attractant of the fall armyworm moth. When the excited moth comes near — zip! — she tosses her sticky ball and snares him. Thus, the perils of following one’s nose.
Flowers fake it too. Many plants depend upon insects for fertilization. Flowers attract insects by offering nectar. Several groups of orchids offer sex, or so it would seem to the unwary bee or wasp. These orchids have evolved flower parts that closely resemble the female insect. The male insect attempts to copulate with the blossom, and — bingo! — he is dusted with pollen. Certain orchids from the Mediterranean are more devious. They broadcast scents that mimic the sex pheromones of the wasps they physically resemble. The wasp comes buzzing in for an assignation, following his sniffer, and leaves with pollen on his feet.
One pheromone whispers “Come hither.” Another shouts “Danger! I am wounded.” Still others say “Food! Join in,” or “Follow me.” A language of scents, with a huge and complex vocabulary. Atoms are the letters. Molecules are the words. And it’s chemistry, all chemistry.
Chemicals are a more subtle channel of communication than sight or sound. For chemical communication to work, the sniffer must be precisely tuned to the scent. A pheromone molecule fits the receptor like lock and key. Humans can hear a dog bark a warning or a grasshopper chirp a love song, but we could be in a cloud of bombykol and never know it. We are mostly oblivious to the huge chatter of pheromones that is going on all around us.
Chemical vocabularies
Since pheromones play such an important role in the lives of so many species, it would be surprising if humans didn’t have a chemical vocabulary of our own. So far scientists have learned little about human pheromones, probably because they are so hard to detect. Perfumers may know more than the scientists. They sell us musk and civet with the promise that those scents make us irresistible to the opposite sex, and maybe they do — at least, they seem to work for the musk deer and the civet, two of our fellow mammals.
On the other hand, we go to great lengths to eliminate our natural body odors, which presumably evolved for some purpose. Maybe deodorants are a prerequisite of higher civilization, allowing us a measure of remove from the unbridled appetites of the civet, which (I have heard it said) is a savage and foul-tempered beast. Perhaps by suppressing the chemical signals that elicit the lusts and aggressions of the rut we manage to keep our musk-deer passions in check.
Maybe achieving our sweeter natures means tuning out the pheromones. Angels (I have heard it said) don’t sweat.
