Storytelling Science

Sex Education

Amitabha Mukerjee


I was recently listening to a conversation on sex between a teenager son and his progressive father:

Son: "The girls in my class have started to behave rather strangely!"
Father: "Oh, they have crossed puberty, and now their sexual instincts are aroused."
[Mother pauses her chay preparation to listen. Dad can't be trusted.]
Son: "But why?"
Father: "Around the age of thirteen, their bodies start making estrogen, which is a hormone that ultimately triggers these sexual feelings. In boys, testosterone that does the same thing."
Son: "But why does this happen?"
Mother [from Kitchen]: "Ashish - have you finished your maths homework yet?"

But seriously, why is it that beyond a certain age, boys and girls begin to find each other interesting? Why do some features in a woman make her more attractive to men, and vice versa? What makes the sexual act, two sweaty bodies rubbing each other, so much fun?

Why is sex fun?

These questions are important not only because they make for great conversation with your teenaged children (and your mother-in-law), but also because they are part of the many questions that define our identity as humans.

What can science tell us about sex? The branch of science that deals with "deep" answers to such questions is Evolutionary Biology, which studies how species evolve. A "shallow" answer is that once the organism is able to survive, the body produces hormones that cause sexual interest. The "deep" answer is that we are all creatures of our genes, and those genes that cause interest in the opposite sex propagated and survived. Those others, which didn't find the opposite sex interesting, rapidly became extinct.

Many of us, brought up the way we have been, are somehow uncomfortable with such answers. However, if you think about it, the logic is unassailable. Consider two women, Arti and Bina: the genes in Arti make her interested in men, but Bina's don't. The chances are good that Bina's genes will disappear in the next generations. Even if Bina's interest levels are lower, ultimately there will be fewer people carrying her genes in the coming generations. Over time, the whole population will gravitate towards showing great interest in the opposite sex. If it hadn't, you and I would not be here.

Sex Appeal

Now let us consider the next question: What features of a female does a male find attractive?

First, a symmetric body is indicative of complete and wholesome development. Second, the skin of the face is singularly indicative of the wear and tear the body has suffered. It is no wonder then, that facial symmetry and a "glowing" skin are two primary measures of physical beauty - not only in humans, but across many species.

Another important issue was that in the millions of years when our bodies (and our brains) evolved, the big question was infant survival. Even in our grandparent's generation, it was common to have only three or four from a dozen babies survive beyond the first year. In periods of food scarcity, the mother wouldn't have enough milk - and an under-nourished child was more susceptible to disease and death. But if the mother's body had a lot of fat, then her body could break it down to make milk for the child. For the male, seeking to maximize the probability that his gene would survive, it was important to select a mate who was high on fat. For women, seeking to attract the best males, it was important to advertise their fat reserves. Using the same Arti-Bina logic as above, you can incontrovertibly show that:

  • Females will develop fat reserves that are prominently displayed on their bodies, (e.g. breasts and buttocks),
  • Males will develop strong genetic preferences for women with such features.
The fact is that despite being cultured twenty-first century Hindustan-Times-readers, we are all carrying the baggage of our many million years of evolution. This evolutionary program is etched into our brains, and expresses itself in our sexuality.

Sexual Signaling

There are many such questions that scientists think they have answers for. For example, why do male peacocks have such extravagant tail-feathers? The fact is that such a tail is a serious handicap in terms of agility, especially in the presence of predators. That a male peacock can survive to adulthood despite such disadvantages tells the female that he is strong and will make a good father. It is what biologists call an "honest" signal, for it comes at a heavy cost. The male behaviour has also evolved to accommodate this, which is why he struts off his tail in the famous peacock dance display.

When you started reading this article, you were wondering what this topic is doing on the Science Page of the paper. By now, if you are like many of my friends and well-wishers, you are perhaps wondering what this person is doing outside a mental institution. But please do not take this lightly, there is matter for much thought in all of this.

Do yourself and the teenagers around you a favour. Discuss these points with them, and if it turns interesting, do drop me a line letting me know!