The Science of Love


Valentine’s Day is right around the corner, meaning that love is in the air…well, love and pheromones and mating calls. That’s right. What better way to approach the season of love and warm affection than with cold, hard, uncaring science?!

It is worthwhile to look at how love, attraction, and mating work in nature. We can start with the feel-good story of the Waved Albatross, a bird that by all accounts is fully monogamous. The male waits expectantly each year for his long-term mate to return from the open ocean so that they may be reunited and resume their biological duty to reproduce and rear offspring. It’s hard not to impart our own human feelings on this species as upon return the albatrosses seem to celebrate by dancing happily and pressing their faces and body against one another.

David Attenborough, when describing the relationship between Waved Albatross mates, says that “if love, as we understand it, exists in nature, then surely this must be it.” However, for many other species, our human definition of love does not apply. The most extreme example that comes to mind is the sea slug, a hermaphroditic aquatic invertebrate. Being that all sea slugs have the capacity to act as either parent, a pair of sea slugs will fight each other to avoid filling the energetically-expensive role of mom. The fight ends in the winner stabbing the loser with its genitalia; therefore, becoming the deadbeat dad. As an extra special tidbit of information, some species have even dabbled in inter-species relations. Most recently, scientists observed Japanese Macaque males mounting and attempting to mate with a species of small deer called a Sika, presumably due to the lack of female macaques in their area.

When we consider the topic of love, we shouldn’t restrict ourselves to the macroscopic world that we see around us. While the romantic displays and courting behaviors of creatures like humans, macaques and beluga whales are fascinating and complex, there is a lot of romancing going on where we can’t see. If we focus our gaze down to the cellular level beyond what can be perceived by the naked eye (hot), it becomes clear that we aren’t the only ones getting busy!

Microorganisms, which vary greatly in size but are typically smaller than the head of a pin (1.5mm in diameter), have extremely short generation times of hours and even minutes. This quick turnover means that many microbes are constantly reproducing in the soil, on countertops, and even on your skin! If that doesn’t get you all hot and bothered, then I guess you are pretty normal because that actually sounds kinda gross…

If that does spark your interest, however, then you will be pleased to know that microorganisms are expert love-makers. To achieve genetic variance between generations, they can engage in various forms of sexual reproduction such as conjugation and transduction. Bacterial conjugation, romantically referred to as a “cell to cell union’, is a one-way transfer of genetic material from one cell to another through a conjugation tube constructed with sex pili (the bacterial thirst is real). Transduction, on the other hand, involves genetic information being transferred from one bacterial cell to another by a bacteriophage virus. Microbial ménage à trois, anyone?

Despite these forms of ‘multi-partner’ reproduction, most microorganism reproduce asexually to rapidly produce a large number of genetically-identical offspring. They can employ a wide range of these techniques, including binary fission (dividing into two) and budding (buds develop at one end of the cell and breaks off as a daughter cell). Therefore, microbes show us that a little self-lovin’ every now and then isn’t a bad thing!

In the spirit of Valentine’s Day, and considering that you probably aren’t a single-celled organism, I will shrink down even smaller and discuss some of the molecule drivers for our feelings of love and affection. At each of the three common stages of love, being lust, attraction and finally, attachment, there are specific molecules at play that help us find that special connection.  

When experiencing lust, the sex hormones estrogen and testosterone promotes feelings of raw attraction and physical desire in both men and women. Attraction, on the other hand, is mediated primarily by dopamine and serotonin, which trigger intense rushes of pleasure and explain why our new lover is constantly on our thoughts. Finally, we reach the stage of attachment when oxytocin (the ‘cuddle hormone’) and vasopressin establish strong biological bonds based on commitment and long-term connection.

Based on this molecular information, suggests that the sure-fire way to fall in love can be achieved in 3 simple steps: 1) seek out a complete stranger 2) spend half an hour revealing your most intimate secrets, and 3) spend 4 uninterrupted minutes in silence staring into each other’s eyes. It really is that easy!

And so, as we quickly approach the holiday of love and romance, remember that science has always got your back! If nothing else, treat yourself to a nice session of binary fission or budding.

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