Answering a question posed by a Hindi film song using Evolutionary Biology
How do you weave प्राकृतिक चयन into a song?
Some Hindi film songs speak deep truths, sometimes by design and other times by accident. In the latter category are songs such as 1 2 ka 4, which has a mathematical truth embedded in it1. Today, we shall move further back in time and explore the deep questions posed by a song from the movie made in 1967. The movie, Diwana, stars Raj Kapoor and Saira Banu. Wikipedia informs us that in the movie, Raj Kapoor plays a simple-minded and extremely naïve man as he does in every movie he has acted in.
Our focus is on the first two lines of a song in this movie.
The lines are
ऐ सनम जिसने तुझे चांद सी सूरत दी है।
उसी मालिक ने मुझे भी तो मुहब्बत दी है।
Raj Kapoor is saying that while Saira Banu is extraordinarily beautiful, it is a remarkable coincidence that he has the ability to be attracted by her beauty. He credits the Almighty for this coincidence.
If you are wondering what the coincidence is, consider this. Raj Kapoor wouldn’t find a female chimpanzee beautiful. He might find her cute as people find some animals to be, but he wouldn’t be romantically attracted to her. The idea of mating with a female chimpanzee would probably gross him out. A male chimpanzee, on the other hand, would find a female of his species extraordinarily beautiful, and would reciprocate Raj Kapoor’s feelings for female chimpanzees when he sees a female of the human species. The coincidence is that heterosexual members of a species are attracted to the opposite sex of their own species. Standards of beauty differ across species, but the survival of a species depends on its members adhering to standards that their opposite gender meet.
What about the Nature vs. Nurture question? Would a feral boy raised by chimpanzees find female chimpanzees attractive? Intuitively, this seems rather unlikely. The ability to feel attracted towards our own species must be innate2.
Then what about preferences for traits within a species? For example, what about a preference for curly haired mates as against straight haired ones? One might think that this preference can be attributed to nurture more than nature, that social standards of beauty, advertisements for fair and lovely, or such other cultural influences decide such preferences. But a quick thought experiment should tell us that if we agree that preference for our own species is innate, then preference for curly hair over straight hair, or vice versa, should also be.
The thought experiment is this: The movie was made almost 60 years ago, and Saira Banu was young then. If you are a young male watching it in 2023, you could find Saira Banu attractive Similarly, I would venture that if you are a young woman, you would find Raj Kapoor (at least the Raj Kapoor of the 50s) handsome.
Raj Kapoor and Saira Banu are as old enough to be your grandparents. Imagine them viewing a movie made 60 years before their time, featuring a lead actor and actress, young at that time, but old enough to be their grandparents. Would they find the actor and actress attractive? Now, because this is a thought experiment, we are allowed to iterate this tens of thousands of times. Every single time, the man and woman viewing finds the woman and man from their grandparents’ generation beautiful and feel an attraction towards them.
But if we take this ancestral movie and show it to you, the young man or woman from this generation, you will find that the actors look slightly odd and a little different from modern humans, even if they are dressed like modern humans. If you go sufficiently far back into the past, our ancestors were as different from us as chimpanzees are. If you look at our chain of experiments though, you will not find any link that is significantly different from the one it is connected to.
It is the accumulation of small differences that has caused us to be very different beings from our forefathers. It must be clear that changes in what we look for in our mates must also have accumulated in similarly small increments. For example, if for some reason, there is a strong selection pressure that favoured curly hair over straight hair, those with a preference for straight haired mates would have ended up single and childless, either due to a shortage of mates or due to the tragic deaths of their mates, as they fell victim to the forces of natural selection. On the other hand, those with a mutation that caused them to be attracted to curly haired mates would come forth and multiply.
In this example, the selection for curly hair came first and the preference for it followed. One can also think of a scenario where it is the other way round. Suppose that you are a straight haired man who prefers a curly haired bride. You look long and hard and you finally find a curly haired woman who prefers a straight haired man. Your children can inherit their hair from either the father or from the mother. Similarly, they can inherit their hair preferences from either. This means that a quarter will have curly hair and prefer curly haired mates, a quarter will have straight hair and are attracted to the straight haired, a quarter will have curly hair, but will look for straight hair in their mates and the last quarter will have the opposite traits.
In other words, in half your children, their type of hair will be the same as their choice of their mate’s hair and half your children will look for a different hair type from the one they have. But in this half of your children, the process will repeat when it is time for them to choose the love of their lives. Over a few generations, the proportion of people who prefer different traits from the ones they have will diminish, and people will increasingly tend to prefer people who look like themselves. Either the curly haired and straight haired will branch off into different species as they accumulate other differences, or one group of people will suffer some accidental catastrophe and get wiped out and only one group remains3.
In other words, the issue raised by Hasrat Jaipuri in the song is valid. To be accurate, the poet needed to replace मालिक with प्राकृतिक चयन4. I don’t know how to work that into the poem, so I will leave the task to more competent shayars5. After all, as Sahir Ludhianvi said a few years before his death:
कल और आएंगे नग्मों कि खिलती कलियाँ चुनने वाले
मुझसे बेहतर कहने वाले, तुमसे बेहतर सुनने वाले
Did you know that this song is a restatement of the Collatz Conjecture? I suppose you do, if you have received any WhatsApp forward.
Obviously, if your sexual orientation is innate, then it is highly unlikely that which species you prefer is a matter of nurture.
Needless to say, this is a huge oversimplification. Just because you prefer curly haired women, it doesn’t mean that you will absolutely not cast a glance at straight haired ones. The strength of the preference matters, and other factors also come into play. Also, there must be a countervailing force where you do not prefer someone too much like you, to avoid accidental incest.
Of course, I owe a huge debt of gratitude to Richard Dawkins whose books helped me understand this. My only original contribution is the interpretation of a Hindi film song.
Strong stuff. I haven’t received any WhatsApp forward related to this. Maybe you should generate one. I’ll forward