When love-birds refer to good chemistry, they may inadvertently be alluding to ‘pheromones,’ a chemical secreted by animals that triggers the phenomenon called ‘smell.’
Unlike other hormones, this chemical influences and changes the behaviour of other animals of the same species and has a role to play in interpersonal relations including sexual attraction.
The effect of the odours triggered by these chemicals known as ecto-hormones is most pronounced in lesser mammals.
Dogs, for example, seek out ‘bitches’ for copulation by the ‘smell’ they emanate during the oestrous period—a regularly occurring period of sexual receptivity in most mammals during which ovulation occurs and copulation is possible. In common parlance, this period is also known as ‘heat.’
As humans evolved over centuries, their sense of smell dulled relative to the development of other powerful sensory faculties. That is, our need to use smell for our survival declined with our evolution, and unlike our pre-historic predecessors we no longer can (or indeed need to) sniff our way to food or our sexual partners.
Even now, however, tribal humans use smell a great deal more than we do for their survival or to support their way of life: by the sense of smell they can, for example, say which animal has passed by a territory and even track them.
Children below four cannot distinguish between good and bad odours. However, as they grow they gain this power.
Pheromones are secreted by sweat glands in human beings post-puberty. The phenomenon of smell is a subject of intense research and is at the heart of the multi-billion-dollar global perfume industry.
It is known that pheromones are present in the areola region, guiding an infant to reach for and start suckling the breasts, which is critical for its survival. Premature babies do not have the help of this smell and hence do not get the first important breast feed.