Valentine’s Day follows Darwin Day by 48 hours. The two seem like polar opposites. One celebrates attraction, and attachment, the other detached rationality and a theory of competitive struggle. In the popular imagination, evolution is about “nature, red in tooth and claw”. The poet Alfred Lord Tennyson coined that phrase in a poem, and it is regularly co-opted to describe the Darwinian perspective. France’s president Emannuel Macron expressed the brutalist conception of natural selection in Davos recently, warning against “a Darwinian worldview”, in which cutthroat competition between nations drove a race to the bottom.

In truth, far from being antithetical to romance, evolutionary biology provides the best framework for understanding it. It reveals, unexpectedly, that romantic love is deeply connected to our capacity for rational thought: we think, therefore we love. It also shows romantic attachments provide adaptive benefits, securing our fitness as individuals and as a species, and are therefore not antagonistic to the competition for resources.

To consider how our capacity for advanced thought led to the evolution of love, and how love, in turn, provided individuals a competitive advantage, let us start with a very un-Darwinian source, the Old Testament’s Book of Genesis. In the biblical story, God places Adam in Eden, and invites the first man to relish the fruit of every tree in the garden, except that of the tree of knowledge of good and evil, which he warns is fatal. God creates Eve as a companion for Adam. One day, she encounters the garden’s resident serpent, who prods her to taste the forbidden fruit. Eve tells him of God’s warning, but the serpent assures her He is bluffing. Curious, she takes a bite, and persuades Adam to do so as well. God finds out and gets very upset. Adam promptly lays all the blame on Eve. Cursing the woman, God cries, “I will greatly multiply your pain in childbirth, in pain you will bring forth children. Yet your desire will be for your husband, and he will rule over you.”

A Darwinian version of the story goes like this: our genus is defined by bipedalism, or standing on two feet. Bipedalism evolved in our ancestor species while their brains were relatively small. However, over the course of two million years or so, that grey matter developed rapidly. They grew progressively more intelligent, which can be viewed as eating the fruit of the tree of knowledge. The physical manifestation of this superior intelligence was a huge brain and head. We possess between three and five times the cranial capacity of our nearest cousins, the great apes. Such development imposes costs, notably in giving birth. Human females undergo a far more difficult childbirth than their chimpanzee and gorilla counterparts. That is the curse that comes from eating the fruit of the tree of knowledge and growing big-headed: in pain you will bring forth children.

Obviously, some million years ago, having bigger brains conferred significant adaptive advantages to proto-humans. But the birth canal and pelvis of bipedal hominids could not keep getting wider to accommodate cleverer babies. Beyond a point, the costs associated with inhibited locomotion outweighed the benefits of bigger heads. Additionally, staying pregnant imposed increasing metabolic costs on females with each passing week. There was, however, an alternate way to achieve enhanced cranial capacity, which was to delay maturity, or, to put it another way, give birth early so that more development could take place outside the mother’s body.

No woman who has carried a child for nine months will think that human birth occurs early. Nevertheless, in terms of development, human infants are nowhere close to being as mature as chimpanzees or gorillas. At birth, our brains are less than a third their final size, while those of chimps have attained 40% of their mature weight. Undeveloped brains cause serious motor control issues, leaving human babies helpless and in need of constant care for months, even years after they are born.

This is not unusual in itself. A number of animals give birth to helpless young: dogs, cats, pigs, and so on. They are known as altricial species. These animals tend to produce bunches of young, spreading risk considerably. Animals like giraffes and horses are at the other end of the spectrum, producing younglings that are up and running within hours of birth. Wildebeest can outrun predators at a day old. Precocial animals tend not to produce litters, not least because each of their newborns is rather large. Humans are virtually unique in producing lone but completely helpless infants. Each baby has already imposed very great costs on the mother, and is therefore extremely precious, but, being born immature, continues to impose massive costs for a long time after birth.

Bond of romantic love

With all the amenities provided by modern nation states, lone mothers are hard pressed to care for their young while also providing for them. Without a welfare or support net, the task gets almost impossible. That is where fathers come in. Having an attentive male greatly improves the chances of an infant’s survival. For this to happen, a relatively long-term bond needs to form between female and male, one that keeps fathers interested in their partners and, by extension, children. That is the evolutionary basis of the bond we know as romantic love. It is strengthened by adaptations like the one enabling human females to be sexually receptive even when they are infertile. There are hundreds of subtler behaviours and traits, far more than we can enumerate, that go into strengthening the bond. It has developed, after all, over hundreds of thousands of years, based on the inter-connected and mutually reinforcing development of bigger brains and early birth. That is what I meant when I wrote, “We think, therefore we love.”

There are a series of caveats that must follow such a strong, biologically-grounded explication of romantic love. First, though romantic love evolved gradually as a mechanism to help big-brained infants survive, it is not specifically directed toward that task, but independent of an individual’s parental prospects. This is similar to the hunting instinct in predators being tied in evolutionary terms to the need for food, but also necessarily independent of it, for if predators only hunted when they got hungry, many more would starve. Consider, in an analogous manner, the nature of the sex drive, which is obviously connected to child rearing in evolutionary terms, but works entirely independent of it as modern societies have demonstrated. Most modern couples attempt to restrict pregnancies without restricting sex.

Just as love is not linked to having children, it is not necessarily linked to persons one could have children with. It is perfectly natural to love members of one’s own sex. Variation, after all, is the driver of natural selection. While there are tremendous variations between individuals in the capacity to form long-term bonds or the directionality of desire, they are not exclusive to particular cultures. That is where the politics of Valentine’s Day becomes relevant.

In India, both the Left and Right get romantic love wrong. (Photo credit: Dibyangshu Sarkar / AFP)

Universality of Valentine’s Day

Both the Left and Right get romantic love wrong. They do so by denying its universality and its profound biological roots. Conservatives in many lands treat it as a Western import, something particularly absurd in India which has a tradition of romantic tales stretching from the story of Shakuntala, mother of the legendary king who gave this country its name, to thousands of Indian films. Leftists do not threaten couples the way conservatives do, but they are equally wrong-headed in classifying love as a social construct, the way they classify most things under the sun as social constructs.

Romantic love is no social construct or foreign import. It went into the very creation of humanity; we would not exist as a species without it. The modes through which the bond between couples is expressed might change from place to place and generation to generation, but its essential nature remains unchanged.

I imagine a window opening in time, allowing us to look back 50,000 years. We peek at a scene in West Asia close to the location of the mythical Garden of Eden. A band of men has been out foraging or hunting and, as they turn to head home with the food they have collected, a youth spots a cluster of bright wildflowers blooming under a tree, the first sign of spring. Asking his mates to wait, he sprints across and plucks a few to take back to his partner. He does not say “Happy Valentine’s Day” while presenting the blossoms to her, but the lovers feel very much as millions of couples will do today when they greet each other with those words.