SEXUAL PHEROMONES
by AbdesSalaam Attar
Part 3
Sexual pheromones
The production of sexual pheromones has two different functions for males and females.
Males must communicate their own values to help females choose a better-value partner.
For the female, the role of pheromones is to communicate her willingness to mate.
Messages communicated through pheromones are not only absolutely reliable because their production depends on the individual’s real qualities, but they can also provide information that no other signal could.
For example, the largest animal produces more abundant sexual pheromones; the best-nourished one produces richer pheromones, and the dominant male of a group produces a pheromone that only he possesses.
A not-banal example that shows the complexity that this “honest communication” can reach is that of one species of butterflies and coleopterans that produce or assimilate from plants’ poisons that protect them from predators. These substances serve the females to protect their eggs, and the males produce a pheromone that is proportional to their provision of poison. The female chooses the most equipped male to transfer this “wedding gift” to her during the coupling.
Usually, the biggest male also has the most considerable provision of poison, which ensures the female of a bigger progeny is more apt to survive and more likely to be selected by the females for mating. If environmental evolution changed and finding the protective poison became difficult, the ability to see it would remain; however, the first criterion for the female to choose the partner, independently of his size.
Experiments with common rats have revealed that females are attracted by the odorous trace of healthy males, and that the trace of males experimentally infected by diseases or parasites lose attractiveness or become repugnant.
However, laboratory experiments reveal that some pheromones allow the animals to recognize their own kin and genetic compatibility. Females prefer males whose immune systems are more different and complementary to theirs, and refuse males nearest to kin who have inherited the same immune capacities.
But the recognition of the genetic inheritance through smell goes beyond that.
Mammals have a sequence of DNA called MHC (major histocompatibility complex). This gene underlies the structure of their immune system. Rats choose to couple with partners that are different in this gene in order to let their progeny acquire a greater resistance to diseases.
This was discovered by chance in a laboratory where two strains of genetically identical rats with only one element of the different MHC had been made to reproduce.
The rats preferred to couple with those of the other lineage.
It was easy to determine that the sense that allowed us to recognize this negligible genetic difference was olfaction.
There are various biological theories to explain how the gene that underlies the immune system is able to condition body smell, but let us suppose that this smell is also able to condition the choice of partner in human beings.
Many cats live in our garden, and all are descendants of only one cat. Any stranger cat coming around is immediately refused. One day, we saw a large cat arriving, and with surprise, I saw my cats smelling it and then leaving it to eat with them. From the spots in his eyes, damaged by an old infection, we recognized our cat that had disappeared years ago when it was still small.
The mother of all the cats was its sister, but she was born after him. No one of the cats had ever known him. It is only its smell that made them recognize their kin relationship.
This shows another aspect related to the olfactory acknowledgment of genetic inheritance. In numerous species, members of the same family recognize each other in order to cooperate.
Human beings are not so far away from their animal nature as it is generally acknowledged. As a perfumer, I noticed how people with a liking or an aversion for a particular scent would recognize it even in a very small quantity blended with many other essences.
Our nose is not at all an atrophied organ, and it conditions many of our choices without our being aware of it. We have just lost the awareness of our olfactory sense.
Each sense has a role in the learning process, and the senses’ education is part of the learning process. Just like the tool in the hand has a significant role in the process of working, learning to use the tool is the beginning of learning how to work. In modern societies, education of the olfactory sense is as primitive as the knowledge of this sense itself. Man knows so much about the cosmos now but does not know how his nose works.
The lack of olfactory educational training from childhood does not impair our olfactory sense. Still, it makes us miss an essential part of knowledge that this organ was designed to give us access to.
The recent discovery of sexual pheromones shows us just one aspect of how our nose indeed controls many of our choices and behaviors, just as it does for all animals…
REST OF THE REPORT ON PHEROMONES:
2. State of the research on pheromones
3. Sexual pheromones (You are here)
