Part 6. Humans are (Blank) -ogamous: Many Intimate Relationships

This is the sixth part on the evolution of human mating behavior, comparing evidence for promiscuity and pair-bonding in our species. Please see the Introduction here.


So be sure when you step, Step with care and great tact. And remember that life’s A Great Balancing Act.” - Dr. Seuss

…………………………………………………………………………………………………………………………………………………………………. Varieties of Intimate Relationships. Click for larger image. (from

David McCandless at “Information Is Beautiful” gave me permission to reproduce the above image. I though it fit well with the series I started months ago titled Humans are (blank)-ogamous, which looked at the evidence for pair-bonding and promiscuity in human evolution. In the first post of the series, I wrote:

To begin, let me say that I side with Sapolsky. Individuals may figure out what works best for themselves in terms of balancing sex, love, intimacy, and commitment, but collectively we are a tragically confused species. …

Across the spectrum of human cultures, we can find examples of heterogamy, endogamy, polyandry, polygyny, monogamy, non-monogamy, polyamory, and so on. However, these do not all occur in equal frequencies, so I don’t think we are truly “blank-ogamous.” There is also lots of room for variation within each culture. Being good Popperians committed to the principle of falsifiability, it is probably easier to say what we are not than what we are. One thing is clear: we are not simple.”

The graphic captures this sentiment nicely, showing the variety of intimate social relationships that humans have negotiated into various socially recognized structures. I wonder if a future version of this might be able to incorporate the frequency of these relationships across various societies, or even the success of them through some measure of happiness or personal fulfillment (though I’m doubtful such data exist).  


Still, while people are behaviorally flexible and are capable of having a wide variety of intimate relationships, this obviously doesn’t mean that we are infinitely malleable in this regard, or any regard. To that point, the biologist Michael Rose was quoted as saying that: “unrestrained free will would be a Darwinian disaster.” It is easy to see: (1) that this observation is true; otherwise all behaviors would have an equal likelihood of occurring, and (2) the logic behind this, since we are evolved animals with finite lifespans who reproduce to ensure genetic perpetuation.

This is not meant to open up a hornet’s nest with a discussion of free will, but there is a reason we are much, much more likely to see skydivers use parachutes than forego them. In Richard Dawkins’ phrasing: “We are survival machines – robot vehicles blindly programmed to preserve the selfish molecules known as genes.” Certainly, one can argue with how well the words “blindly programmed” fit human beings, as opposed to a virus, for example. If someone was so inclined, they could skydive parachute-free. But that would be a spectacularly unsuccessful route for a survival machine to take, and anyone choosing that route would have fewer disciples and descendants than those from the parachute school of thought. There may not be a parachute gene or genes, but there are genetics involved in fear, the stress response, and assessment of risk. 

Similarly, evolution is not merely about survival, but also reproduction. To that end, the psychologist Geoffrey Miller has argued that: “our minds evolved not just as survival machines, but as courtship machines. Every one of our ancestors managed not just to live for a while, but to convince at least one sexual partner to have enough sex to produce offspring” (Miller 2000: 3). And good for them, or else we wouldn’t be here.

Certainly, there are genes involved here as well. For example, in a study of 181 young American adults, Justin Garcia (2010) and colleagues reported that individuals with one version of the dopamine D4 receptor gene were more likely to engage in extra-relationship sexual experiences (i.e., infidelity) or have one-night stands. The authors noted that this allele was associated with sensation- and novelty-seeking behaviors in other studies, but were quick to add that it would be overly simplistic to refer to this as a “promiscuity gene” (tell that to the media). Rather, it seems that our courtship-sculpted minds seem to have multiple erotic “programs” that we try to keep in some sort of balance, of which sexual gratification may only be one. Importantly, these programs are always running within the context of a given culture, which individuals must learn to navigate. As Garcia et al. put it: 

While sexual reproduction remains the currency of evolution, cultural regulation of sexual behaviors constrain the evolutionary best interests of individuals within a population. We suspect that the associations we observed between dopaminergic sensation-seeking and sexual behavior may be independent of other evolved mechanisms that promote pair-bond stability and romantic attachments.” (emphasis added)

Greg Downey, in his post The Long, Slow Sexual Revolution, referred to something along these lines when he wrote that humans have a “flexible, even contradictory sexuality” that defies simple description. Furthermore, that flexibility might be adaptive in that it could operate under fairly rapidly changing social/ecological conditions. Perhaps that is how our species arrives at something like the graphic at the top of this page, with many possible intimate relationships. (This is to say, things would be a lot simpler if we were birds of paradise, and we could just perform – or judge – a little song and dance for potential mates). 

The larger point is that human behavior, including sexuality, is always expressed within cultural contexts. In a wonderful piece on human nature, Jason Antrosio wrote that “there is no such thing as human nature, no core of humanness outside of particular histories and circumstances.” This isn’t an argument that culture is disconnected from our biology. In “The Origins of Virtue” Matt Ridley (1998) described the relationship between the two as follows:

our cultures are not random collections of arbitrary habits. They are canalized expressions of our instincts. That is why the same themes crop up in all cultures – themes such as family, ritual, bargain, love, hierarchy, friendships, jealousy, group loyalty, and superstition.”

We obviously have a lot of cultural diversity in humanity with substantive differences in worldviews and which behaviors are deemed acceptable, but cultures – and individuals – are tasked with how to balance sex, love, intimacy, and commitment, as well as reproduction and parenting. I think this interplay between individual drives and cultures provides an alternate model of looking at things rather than trying to discern what humans ‘are’ in terms of our sexuality.   

But it is important to remember that the arrows of causality between biology and behavior are multi-directional. If our biological impulses originate from our evolutionary histories, how they are expressed occurs within a given cultural context, which is negotiated over time by a collective of individuals. An analogy can be found in thinking about how organisms grow and develop. In “The Triple Helix,” Richard Lewontin wrote that:  

the relations of genes, organisms, and environment are reciprocal relations in which all three elements are both causes and effects. Genes and environment are both causes of organisms, which are, in turn, causes of environments, so that genes become causes of environments as mediated by the organisms.” (2002: 100)

That is somewhat complicated, but Lewontin might say that no living thing develops in a vacuum; there is no such thing as an organism without an environment. Nor is there a human without culture. In terms of sexuality, our biological impulses have genetic roots, and individuals learn cultural norms as to the various ways those impulses might be appropriately expressed. But there is one more step. Individuals do not just passively receive cultural norms; they also construct them. And different cultures, at different times, have come up with various prescriptions to balancing our diverse needs. 


Part 7: Is It Possible to Love More than One Person (July 2012)

Part 8: Evolution, Love, and Suffering (Feb 2013)


Garcia JR, MacKillop J, Aller EL, Merriwether AM, Wilson DS, Lum JK. 2010. Associations between dopamine D4 receptor gene variation with both infidelity and sexual promiscuity. PLoS One. 30;5(11):e14162. (Link)

Lewontin R. 2002. The Triple Helix: Gene, Organism, and Environment. Harvard. (Link)

Miller G. 2000. The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature. (Link)

Ridley M. 1998. The Origins of Virtue: Human Instincts and the Evolution of Cooperation. Penguin. (Link

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7 thoughts on “Part 6. Humans are (Blank) -ogamous: Many Intimate Relationships

  1. Pingback: Anthropology on Sex, Gender, Sexuality - as Social Constructions

      • Agreed. I love bowerbirds too (there was a great National Geographic spread a few years ago: as examples of the dynamics of courting behaviors out there. In this video, I especially like the implication that the ecological relativity of food abundance drives this behavior. I will have to work this into my Anthropology of Sex course. I often show them “The Science of Sex Appeal,” which has a segment on male’s showing off their lowriders & the girls who love them. One student (sort of missing the point) said, “but I don’t care about my boyfriend’s car.” What drives people do show off in ways that are not just I-killed-a-wild-boar-for-you-darling-here’s-the-bacon (heteronormatively speaking, that is). My problem is that I also got the criticism that I talk too much about animals & not enough about humans, so your post will give me some help. Thanks!

  2. Pingback: Patrick Clarkin’s Humans are (blank)-ogamous Series | Welcome to the EvoS Consortium!

  3. This particular post was a little bit vague, but I’m glad you resisted the temptation to place strong reliance on anthropological studies which have regularly been found to be in error, and I’m not just talking about the well-known Solomon Islands study on premarital sex. Someone spends a few weeks in some third-world rural village and produces a paper that extrapolates a claimed newly-identified behaviour onto the whole of humankind.

    A few times in this series you’ve appeared to fumble your way around the concept of normality and I wondered if you’re aware of the five categories of Normalcy in a society. Behaviours can be grouped into Compulsory, Preferred, Typical, Alternative, or Restricted.

    I continue to read in great fascination…

    • It’s funny, but I think this post was one of my favorites in the series, perhaps because I forced myself to address the complexity of many moving parts interacting together.

      I have a higher opinion of ethnographers. I suppose it’s difficult to capture what any group of people believe because this will fluctuate over time, and there will also be variation within any group. But cultural anthropologists are held to a pretty high standards by their doctoral committees as well as the journals they publish in. And, they are often our only source of knowledge. I’m not sure which study on the Solomons that is, but the famous Margaret Mead one on Samoa seems to be vindicated. I’ll leave that to the ethnographers though.

      Thanks for the kind words and the tips on normality. I do struggle with ‘normality’ because I think about it in a biological/mathematical point of view in a bell curve sense. Statistical thinking is often not very intuitive. Your terms help. I’ll read up on it.

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