The reason humans fall in love is evolutionary. From a biological perspective, this set of feelings we call love has allowed the human species to reproduce and thrive. It is known, in fact, that romantic love and all the activities associated with it lead to the acquisition and maintenance of certain behaviors necessary for creating an emotional bond between partners and raising offspring together.
The emotions we experience when we're in love alter our behavior , pushing us to commit to a relationship and bond emotionally with our partner and, if we have children, with our offspring. It's not romantic at all, is it?
The partner as an adaptive response
If sexual desire is the means to procreate, then falling in love has created the concept of "family." Finding a partner and creating a more or less lasting emotional relationship with them is simply a way to provide the unborn child with a safe and peaceful environment in which to grow. Similar behaviors to those seen in humans have also been observed in other species; for example, some birds choose a specific partner to mate with and raise their young together.
The adaptive response...
The pair bond evolved as an adaptive response to the need for greater parental investment in raising young. By adaptive response, we mean the capacity of living organisms to change their metabolic, physiological, and behavioral processes, allowing them to adapt to the conditions of their environment.
In other words, romantic relationships and their persistence are an evolutionary necessity in species where biparental care of offspring was fundamental. Unlike most animal species, females typically give birth to one child at a time . The child is not self-sufficient for several years after birth, which is why the presence of adult caregivers—who may be members of the nuclear family, that is, both parents—becomes necessary.
The organ of love – the brain
The brain, not the heart, is responsible for the diverse range of emotions we experience from falling in love to suffering the pain of a broken heart. This is all due to specific molecules, neurotransmitters that act in the brain: testosterone and estrogen, dopamine, serotonin, adrenaline, norepinephrine, oxytocin, and vasopressin , commonly referred to as the "love and attachment hormones ." These come into play during the three main phases of falling in love : desire, attraction, and attachment.
If we fall in love, we wish
Imagine you're in a nightclub. As you look at the crowd, your attention is drawn to a single person. Something about them captivates you, and you want to get to know them. Why? This desire, dictated by factors involving our five senses , is nothing more than a search for sexual gratification. The evolutionary motivation for this behavior lies in the need to reproduce, a need shared by all living beings. It is precisely our five senses that provide the brain with the information necessary to enter the first phase of falling in love.
Sex hormones
The hypothalamus plays an important role in this process. By receiving specific external stimuli (sight, hearing, etc.), it promotes the production of sex hormones such as testosterone and estrogen by the testes and ovaries, respectively. One study has shown that testosterone increases libido in almost all the men examined. The effects are less pronounced with estrogen, but some women in the study reported being more sexually motivated at the time of ovulation, when estrogen levels are highest.
Love enters through sight, whatever they say
Sight is often the first sense involved in the initial stages of falling in love. What we consider "beautiful" is generally dictated by the intrinsic beauty standards of the country where we grew up. In general, however, youthful, shapely, shiny, thick, soft, and healthy hair tends to be considered attractive. These are all indicators of reproductive fitness and, therefore, suggest that the person we are looking at could be a good candidate for mating and producing healthy offspring.
we fell in love by smell
Smell is the sense that comes into play once you approach another person. We're not only attracted to their perfume, but also to a series of volatile molecules called pheromones . These transmit a whole range of physical and genetic information from their source and trigger physical and behavioral responses in the receiver.
A study conducted to demonstrate the effects of pheromones involved a group of women and a group of men. The women were required to wear a shirt for three consecutive nights, and then the men smelled it. In the men, an increase in testosterone production (and therefore libido) was found only after smelling the shirts of the women who were ovulating at the time.
hearing, taste and touch
Hearing also "activates" desire. Men are attracted to high-pitched voices, while women are attracted to deep voices. Even touch and taste contribute to the search for the best candidate. Touching and kissing the other person allows our brain, from the very first time, to quickly assess the subject at hand and decide whether or not they are a good match. A kiss, for example, is a rich and complex exchange of chemical and tactile cues that help the brain make decisions. It is precisely for this reason that many relationships are cut short after an unsatisfactory "first kiss."
We can say that it is our brain, aided by the 5 senses , that makes us "want" the best candidate!
Attraction
Once you get past the first stage and begin a relationship with the other person, you enter the attraction stage . Attraction involves brain pathways that control reward behavior.
When we talk about the reward system, we're referring to a series of brain structures that activate when they detect rewarding stimuli . For example, when we eat our favorite food, read a book we've been waiting for, or do anything else we enjoy, the brain releases a specific neurotransmitter: dopamine, which produces a feeling of well-being . This is how the mechanism that drives us to seek out that particular experience is triggered. The purpose of this brain circuit is, therefore, to ensure our motivation toward certain behaviors that the brain deems necessary. Reproduction and the perpetuation of the species are such behaviors, and are thus driven by the reward system.
I get dopamine...
Spending time and having regular sex with your partner creates high levels of dopamine and a related hormone, norepinephrine, which are produced and released by the brain during this stage. Both strengthen the reward system, which is why the more we're with the person we're in love with, the better we feel and the more we want to spend time with them.
The surge in norepinephrine typically produces insomnia and loss of appetite , along with heightened alertness and improved memory for new stimuli—all hallmarks of the early stages of human love. Norepinephrine is also associated with the peripheral sympathetic nervous system, leading to an increased heart rate, sweating, and trembling. Who hasn't lost their appetite or had trouble sleeping because they were too preoccupied with thinking about their loved one?
we fall in love by attachment
Attachment is the stage where long-term relationships develop. While desire and attraction are almost exclusively associated with romantic relationships, attachment is the phase of "sharing" with friends, parent-child bonds, and so on. The two main hormones in this phase are oxytocin and vasopressin.
Like dopamine, oxytocin is produced by the hypothalamus and released in large quantities during sex, breastfeeding, and childbirth . This may seem like a strange array of activities (not all of them necessarily pleasurable), but the common factor is that all these events are precursors to the bond that will be formed.
In romantic relationships, as the bond strengthens, levels of oxytocin and vasopressin rise, transforming sexual desire into a "tender love." At this stage, attraction and sexual desire are partially replaced by a less passionate, but stronger and more lasting, emotional connection. Oxytocin is often nicknamed the "cuddle hormone" for this very reason.
We can conclude by saying that desire drives people to mate, attraction to prefer specific partners, and attachment motivates people to stay together long enough to complete parenting tasks.
Conclusions
We like to think that love is something spontaneous that comes from the heart and that fate plays a role when we find the right person, but unfortunately, it's not like that! It's our brain that decides the fate of a potential relationship in a fraction of a second and, if that's the case, allows us to create a more or less lasting emotional bond.