Love: can biology define it?

By: Sophia Wang

Photo from Wix images.

From ancient philosophers to the average modern-day blog writer, humanity has wrestled with one question: what exactly is love?

One of the first known mentions of love is associated with Empedoscle’s theory on cosmology [1]. Empedoscle was a Greek philosopher from around 450 BCE who described Love as a fundamental cosmological force that united different elements (fire, water, earth, and air) to create the universe and all beings within it. Conversely, he theorized that there was an opposing force, Strife, that worked to divide different elements. Empedoscle further postulated that Love and Strife existed in a dynamic equilibrium and accounted for all processes of creation and destruction [1].  

Love today has drastically different meanings, primarily centered around emotions of care, affection, and attachment [2]. Across literature and other media, I’ve seen love depicted in myriad ways: as simple crushes, a healing force for both parties, or perhaps unconditional sacrifice for one another. Love assumes a wide variety of synonyms as well: loyalty, commitment, honesty, trust, gratitude, empathy, and so on. Thus, I’ve learned that love is ubiquitous, yet everyone will define it differently. Although this nuanced, individualized conceptualization raises challenges for scientific research on love, it has not prevented researchers from attempting to examine the subject through a biomedical lens. 

A Sprinkle of Love (Neurology)

Love can be classified into many categories, such as love for one’s family, friends, romantic partners, pets, and even strangers. Interestingly, love for nature is among the most commonly experienced types of love [3]. Different kinds of love can involve different regions of the brain (Figure 1) [3]. 

Figure 1. Brain regions activated (red) or deactivated (blue) by different types of love [3]. 

Love is in the Air Hormones

From an endocrinology perspective, love can be very roughly distilled into 3 emotions: lust, attraction, and attachment [4]. Different hormonal processes underlie each emotion:

• Lust: a desire for sex, driven by: 

  • An increase in testosterone (for males and to a lesser extent, females).

  • An increase in estradiol, a type of estrogen (exclusively relevant for females).

• Attraction: an emotion that drives obsessive, exhilarating thinking and motivates rewarding behaviours, driven by:

  • A decrease in serotonin, which contributes to obsessive thinking.

  • An increase in noradrenaline, which contributes to giddiness, euphoria, and affects sleep.

  • An increase in dopamine, which is involved in our reward system.

• Attachment: an emotion more prevalent in long-term relationships. From an evolutionary perspective, it may serve to enable cooperation between mates to complete parental duties. Attachment is primarily driven by:

  • An increase in oxytocin, which facilitates bond-forming.

  • An increase in vasopressin, which interacts with other hormones such as oxytocin and dopamine. Thus, it is involved in attraction as well as attachment-related bond-forming [4].

    
    

This, however, is a highly simplified and generalized version of what is likely a very, very complex process. Numerous factors besides hormones can influence the way each person experiences love—ranging from cultural norms to the makeup of the gut microbiome [4,5].  

Outro: A Heartfelt Two Cents 

Ultimately, love is a complex, multi-faceted phenomenon unique to each person. Numerous factors like biological and environmental influences can affect the way one experiences it. Yet, there is beauty in such diversity, as it allows each of us to celebrate a different kind of love. As Valentine’s Day has recently passed, perhaps it is worth asking ourselves: what kind of love I would like to celebrate going forward? 

References

1. Kingsley KS, Parry R. Empedocles [Internet]. Stanford University; 2024 [cited 2026 Feb 9]. Available from: https://plato.stanford.edu/entries/empedocles/#Cosm

2. Love [Internet]. Merriam-Webster; [cited 2026 Feb 9]. Available from: https://www.merriam-webster.com/dictionary/love

3. Rinne P, Lahnakoski JM, Saarimäki H, Tavast M, Sams M, Henriksson L. Six types of loves differentially recruit reward and social cognition brain areas. Cerebral Cortex [Internet]. 2024 Aug 26;34(8). Available from: https://academic.oup.com/cercor/article/34/8/bhae331/7741043 doi:10.1093/cercor/bhae331

4. Robinson JM, Crino OL, Camargo A, Breed MF. Does a microbial-endocrine interplay shape love-associated emotions in humans? A hypothesis. mSystems [Internet]. 2025 Jul 14;10(8). Available from: https://journals-asm-org.libaccess.lib.mcmaster.ca/doi/10.1128/msystems.00415-25 doi:10.1128/msystems.00415-25

5. Abou Haykal MA. The Roots of Happiness: How Love and memory shape the core of our brain. Progress in Brain Research [Internet]. 2025 Apr 2 [cited 2026 Feb 9];293:41–55. Available from: https://www.sciencedirect.com/science/chapter/bookseries/abs/pii/S0079612325000305?via%3Dihub doi:10.1016/bs.pbr.2025.03.002