We often think of “love” as the center of understanding romantic relationships but that is not the whole, or the most accurate, picture. We know that humans pair bond and are frequently in monogamous sexual and social relationships, but that does not mean what you think it does: love ≠ romantic relationship ≠ monogamy ≠ pair bond.

So what is love? Unfortunately, the answer that some people seek involves a philosophical and/or spiritual question that is way beyond the scope of this blog. However, I can slightly rephrase the question to ask: what is going on in the body when people feel strongly towards one another and why are these feelings so powerful?  Which is really what many people mean when they talk about “love.”

Answer #1: the biology of attachment. We know that a suite of hormones and neurotransmitters (including oxytocin, vasopressin, prolactin, testosterone, dopamine, etc…) are involved in developing and maintaining physiological bonds between mothers and infants and fathers and infants. This system also functions in the same way between adults.  The system is triggered by physical touch, spending intense social time in contact or near one another, and positive social interactions. Humans have evolved a system that uses social and physical interactions, hormones, and the brain, to prime the body to feel closer and more attached to another individual.  In the most basic sense this is the same system common across mammals.  The anthropologist Walter Goldschmidt called this “affect hunger[i]”  and suggested that the basic system that acts to bond mammalian mothers to their infants has been expanded and co-opted in the human species to act as a social and physiological bonding system between individuals of all ages and sexes.  This drive of affect hunger enables humans to form and experience types of social bonds across a wider range of individuals and with more intensity than in other animals, even than other primates.  Many researchers argue that it is these bonds which have enabled humans to do better than almost any other organism on the planet[ii].

So one answer to “what is love” is that it is the biology underlying affect hunger, the ability to form multiple strong social bonds and part of the human adaptive niche, the evolutionary history that has made us so successful as a species. This view suggests that what is called “love” has the same base between parents and offspring, between siblings or other family members, between good friends, and even between romantic pairs. 

But most people want “love” between romantic pairs to be something different. Culturally we see romantic love as separate from familial or friendship love.  Unfortunately, aside from a slightly different pattern of some specific hormones brought about by sexual behavior, there is nothing truly different about romantic love than any other kinds of love.  Biologically speaking that is. Of course there are various different psychological and social elements involved, as well as religious ones, in what people see and experience as romantic love. However, the myth that romantic love is essentially (biologically) different from other types of strong attachment is created and maintained by cultural beliefs and our world views, not our biology. What most people are really trying to get at when they try to figure out romantic love is to explain the particular strong relationship between two people we call the “pair bond” (which is answer # 2).

In the basic biological sense a pair bond is a special, predictable relationship between two adults.  When researchers look to humans (and some other mammals, especially primates) this is refined to focus on a special and predictable relationship between a male and a female that involves tight social connections and a sexual affiliation, and usually includes mating and the raising of young. It is often stated that this pair bond is the basis of human society and that we can look to our evolutionary heritage to see that it is a major, early event in human evolutionary history[iii]

However, pair bonds are not exactly what many think they are and they are not necessarily linked to procreation and the nuclear family in human evolutionary history. There is substantial evolutionary evidence that humans do seek pair bonds (both social and sexual), but these bonds do not necessarily involve sex, marriage, exclusivity, or even heterosexuality.  Marriage is not equal to evolutionary or physiological pair bonds, the nuclear family is not the basal unit of human social organization[iv].   

Humans have extensive social pair bonding across genders and age categories, probably more than any other species. Humans have both social and sexual pair bonds, and the two are not necessarily connected.  We can have social pair bonds with our relatives[v] and our closest friends, they can be with same-sex individuals or different sex individuals, same-age or different ages. Humans are also unique in having sexual pair bonds both heterosexually and homosexually[vi].  Our sexual pair bonding, like our sexual activity, is not limited to reproduction

Pair bonds, both social and sexual, in humans are part of complex social networks that emerged as a core pattern in human evolution.  Pair bonds can involve sexual relationships (and in a cultural sense, romantic attachments) and are probably involved in what most people experience when they think of romantic love. But pair bonds are not the same as marriage and they are not necessarily connected to monogamy or a particular sexual orientation. But they are an important part of being human.

Love is not a thing or a pattern.  It is simply a word that we use to gloss over the amazingly diverse, complex, and even messy, realities of human relationships. And as always, being human is much more interesting than that.

[i] Walter Goldschmidt (2005) The Bridge to Humanity: How Affect Hunger Trumps the Selfish Gene Oxford University Press

[ii] This notion is increasingly popular in studies of human evolution. For an overview of these ideas see Fuentes, A. (2009) Evolution of Human Behavior, Oxford University Press.

[iii] For recent versions of this approach see Chapais, B. (2008) Primeval kinship: how pair-bonding gave birth to human society. Harvard University Press, and Lovejoy, O. (2009) Reexamining human origins in light of Ardipithecus ramidus. Science 326:108-115

[iv] These facets of relationships and sex are covered in an extended format in the fascinating book”Sex at Dawn” (Ryan, C. and Jetha, C. (2010) Sex at Dawn: The Prehistoric Origins of Modern Sexuality. New York, Harper Books).

[v] However, just being a relative does not automatically generate a pair bond.

[vi] See Fuentes, A. (2012) Race, monogamy, and other lies they told you: busting myths in human nature (UC Press) for an overview of data and perspectives n this topic.

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