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February 14, 2019

Love, oxytocin and evolution

Filed under: Evolution,love,oxytocin,science,valentines-day — Razib Khan @ 1:52 am
Gibbons form pair-bonds

On some level, most scientists would say that everything is reducible to material and mechanism. But to say that “everything is due to the swerve of atoms” doesn’t get us much further than the ancient Greeks, who were the first to elaborate on such materialist ideas philosophically.

At the other extreme from scientists are those humanists who assert that concepts such as “love” or “hate” are not reducible to scientific analysis and decomposition. In this framework, love and hate are both emotions which exist in a particular social and cultural context, and general systematic analysis may miss the forest from the trees.

But if physics does not offer answers beyond the trivial, a better understanding of behavior or mental characteristics can be obtained by looking at sciences such as cognitive neuroscience and evolutionary biology, which exist at a higher level of phenomenological complexity. Behavior comes from the mind, and the mind is an expression of the brain, which itself is shaped by evolutionary pressures.

Romantic love as an emotion then exists in the context of our evolutionary history, and that history likely has something to do with mating and pair-bonding. Our “reproductive fitness” is conditional on the very act of mating, and often survival is dependent on aid and help from others. For birds, monogamy is so common because both parents are often required to warm and tend to eggs. In mammals, in contrast, males tend to be less involved in provisioning for offspring. But there are exceptions.

An “alpha couple” among wolves

Wolves, and some primates such as gibbons and humans, tend to be monogamous. This is evident in the minimal difference in the size between the two sexes, as well as genetic data which shows that the “effective population size” of males and females over time has been in the same order of magnitude. That is, a reasonable proportion of both males and females contribute genes to the next generation.

Humans have extended childhoods

One reason that humans have elaborate emotions related to bonding seems to be that our childhoods are extremely long. This means that parents, and in particular the mother, develops a strong bond to their offspring, which is reciprocated. In the complex social systems of our species feelings of connectedness extend to kinship, and the bond between mates is solidified with romantic love and companionship. Love comes in many forms in our lineage, but it is clearly a feature and not a bug.

This is ultimately a consequence of genetics. The tendency toward prosociality and empathy seem to be heritable. That is, some of the variation of the characteristics within a population is due to variation in genes. This is clearest in prairie voles, where different species exhibit radically different behaviors in relation to bonding and mating, and also different genetic profiles.

Individuals with more “G” allele have more empathy

In humans, the neuropeptide oxytocin has been implicated in variation in characteristics such as empathy and bonding. This research began with relatively small samples, but a recent study with 1,830 individuals reports a single mutation with the OXTR locus is associated with variation in empathy. This is not entirely unreasonable in light of the fact that in the modern human population there are differences in personality, and dispositions, including empathy. The persistence of various personality types indicates that there’s no singular way in which one maximizes long-term fitness, but many alternative strategies (within limits).

Romantic love in terms of its biological basis may have a fundamentally material and evolutionary origin: a tight bond between parents results in a greater likelihood that offspring grow up to adulthood. It emerges from a complex set of neurobiological pathways, which themselves vary due to genetic factors from person to person.

But just as sugar is a molecule we understand but find still delicious, so the sweetness of love remains even after unmasking the underlying science.

Interested in learning where your ancestors came from? Check out Regional Ancestry by Insitome to discover various regional migration stories and more!


Love, oxytocin and evolution was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

February 13, 2019

The Insight Show Notes — Season 2, Episode 14: Love & biology

Filed under: Evolution,love,valentines-day — Razib Khan @ 6:51 pm

The Insight Show Notes — Season 2, Episode 14: Love & biology

This week on The Insight (Apple Podcasts, Stitcher and Google Podcasts)we discuss “love” from the perspective of an evolutionary biologist. More specifically, we had a wide-ranging discussion with Steve Phelps, a professor at the University of Texas in Austin. He studies the intersection of behavior, evolution, and neuroscience, with genetic tools.

First, we addressed whether love is a cultural invention of the last few thousand years. Particularly, of the West.

The reality is that love, and in particular romantic love, is a primal urge that likely existed in the environment of our “evolutionary adaptedness.” But its particularities are cultural. There is a lot of diversity “on top” of the basic source code. But there is a human universal we recognize.

We talked about inclusive fitness and the origins of love as an emotion in socialization. In particular, the common neurological and evolutionary origins of love in the context of parent-child, family, and partners.

A debate emerged about whether humans are ancestrally “monogamous” or “polygamous.” The terms differ in definition across discipline (genetics, behavior, anthropology), but the consensus seemed to be that we’re more monogamous than gorillas or chimpanzees.

There was much discussion of the literature on the association between empathy at the OXTR locus. Mostly commonly studied in voles, there are also suggestive results in humans. But much work needs to be done!

We talked Helen Fisher’s work in the neurobiology of love and attachment, and her excellent books such as Anatomy of Love.

Steve finished with a discussion on frequency-dependent selection, and how a diversity of behavior and disposition might be maintained.

Interested in learning where your ancestors came from? Check out Regional Ancestry by Insitome to discover various regional migration stories and more!


The Insight Show Notes — Season 2, Episode 14: Love & biology was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

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