All three theories could be true. In particular, the role of perfume as an olfactory disguise is obvious. Even here, however, there are some subtle twists. Bad smells are not just a matter of poor hygiene. Illness and old age both bring characteristic odours of their own, and neither state makes people more attractive. Perfumes may spoof these messages. Hence the marketing of a new scent called Ageless Fantasy, by Harvey Prince, which claims its product disguises the “odour of ageing”, suggested to be caused by the breakdown of a particular fatty acid in the skin.

As to pheromones, whether humans have these is questionable. A pheromone is a chemical that elicits a specific behavioural response at a distance. Some insects, for example, can release sex pheromones that will attract a mate from many kilometres away. The most likely human candidate is a substance called androstadienone. This is a derivative of testosterone that is found in men’s sweat and is known, from brain-scanning studies, to promote activity in parts of women’s brains. That this results in changes in behaviour has not, however, been clearly demonstrated.

Terri Molnar, a spokeswoman for the Sense of Smell Institute, a research organisation in New York tied to the fragrance industry, says of human pheromones, “I think we believe they exist but they do not function as an attractant. They will elevate one’s mood but not attract a mate.”

The fallen sons of Eve?

The most interesting area, though, is the interaction between perfumes and natural scents that carry messages but do not have the specific properties of pheromones. Odours co-ordinate a wide range of human behaviour. Mothers can recognise their children by smell. Children can recognise each other. Relatives can be distinguished from non-relatives, even to the extent of understanding who is genetically different enough from the smeller to be a good choice of mate. The sexes themselves smell different, too, and women can glean information about a man’s social status from his smell alone.

... contd.