Did Pairbonds Evolve to Be Asymmetrical?

“I know you belong to somebody new, but tonight you belong to me.” Rose and David 

“I wanted love, I needed love. Most of all, most of all.” Auerbach and Carney (1)


Several researchers have attempted to reconstruct the very difficult problem of why pairbonding may have evolved in humans (I wrote about this here, but a decent guess is that this began around 2 million years ago. Maybe). Those reconstructions often come with an addendum, which predict that pair-bonds would not be completely symmetrical. Instead, either males or females would have more of an incentive to initiate or maintain a long-term bond, and this would depend on the reasons that pairbonding evolved in the first place.

For example, here is David Buss, explaining why males are more likely to fall in love first:

“Because love is an emotion tethered to long-term mating; because fecundity and reproductive value is so critical to men in selecting a long-term mate; and because physical appearance provides an abundance of cues to a woman’s fecundity and reproductive value, we can predict that men will experience “love at first sight” more often than women. The empirical evidence supports this prediction.” (Buss, 2006: 69)

Australopithecus afarensis ("Lucy"), out with her date. Source.

Australopithecus afarensis (“Lucy”), out with her date around 3.6 mya. This portrayal of an early pairbond is speculative, but it ‘s probably not accurate. Source: AMNH.

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Part 13: Humans are (Blank)-ogamous: Is Monogamy ‘Natural?’

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


(Left) My paternal grandparents with my father as a toddler. (Right) Their 50th anniversary.

Left: My paternal grandparents with my father as a toddler. Right: their 50th wedding anniversary (it’s the best picture I could find).

Are humans naturally monogamous? Oprah Winfrey says ‘no.’That settles it, then. Maybe.

Oprah (she needs no last name) was a guest on a morning talk show, and the topic of discussion was two recent articles on the origins of monogamy in mammals (Lukas & Clutton-Brock, 2013) and another specifically on primates (Opie et al, 2013). Both articles are impressive for their large databases and attention to detail. The first looked at 2545 species of mammals while the Opie article examined 230 primate species.[1]

Both studies focused specifically on social, rather than sexual, monogamy. This distinction is important because sexual exclusivity was not what was being measured here. Rather, social monogamy was defined by both studies as simply living in breeding pairs. The Lukas & Clutton-Brock paper added that in social monogamy the pair shared a common territory, and “associate with each other for more than one breeding season” (p. 526).

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The Zen Master and the Infanticidal Primates

A recent paper has concluded that prevention of infanticide was the most likely precursor to monogamous mating systems in some primate species. Another paper suggested a different possibility in mammals more generally, namely that under certain ecological conditions females are so dispersed that the best strategy for a male is to remain close to a rare female when he finds her. This prevents other males from mating with her, and increases the chances of successfully passing on his genes. 


Langur mother with dead infant. (From http://www.brown.edu/Research/Primate/LPN50-1.html)

I’m still sorting through what all this means, and wonder if the search for broad patterns oversimplifies things too much. As Peter Gray put it: “It’s all so confusing, if lead researchers can’t seem to find similar evolutionary grounds behind social monogamy.” Anyway, if prevention of infanticide really was the key to jump-starting monogamy (at least in some primate species), it makes me think of its downstream consequences. This reminds me of the parable of the Zen Master and the Little Boy.

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Part 12. Humans Are Blank-ogamous. Jankowiak’s Tripartite Conundrum

This is part 12 of a series on the evolution of human mating behavior. Please see the introduction here.

This video is a lecture by the cultural anthropologist William Jankowiak speaking at my alma mater, Binghamton University, on what he calls the “tripartite conundrum” between romantic love, companion love, and sexual desire. I think he has several insights, but realize that the lecture is lengthy.  If you can’t listen to it in its entirety, here is the heart of the matter:

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Part 9. Humans are (Blank)-ogamous: Love Is an Evolutionary Compromise

This is part 9 of a series on the evolution of human mating behavior, comparing evidence for promiscuity and pair-bonding in our species. Please see the introduction here.


I want love to roll me over slowly,
Stick a knife inside me, and twist it all around.
I want love to grab my fingers gently,
Slam them in a doorway, put my face into the ground. – Jack White (Love Interruption[1]  

“Everything is a double-edged sword… Even single-edged swords are a double-edged sword. Because you can cut something with it, but the other edge is kind of flat and it doesn’t cut very well.” – Louis CK (comedian)



Yesterday’s post looked at the neurobiology of romantic love, asking whether evolutionary perspectives are sufficient to explain this highly significant part of what it means to be human. It also raised the question as to why love seems to be a painful experience for so many people.

Before going further, it’s important to remember that while humans are undoubtedly evolved, biological organisms, we are also animals with complex behavior, language, and culture. Others have said this better than I can. To Jon Marks (2010), we are “biocultural ex-apes,” while Agustin Fuentes wrote that “human behavior is almost always ‘naturenurtural’ ” (2012:16). Just as human modification of the environment can affect natural selection (Hawks et al 2007; Laland et al. 2010), so can culture profoundly influence the way we interpret powerful emotional impulses, including those related to desire and love.

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Part 2. Humans are (Blank) -ogamous: Promiscuity

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


I’ll be frank. True monogamy is rare. So rare that it is one of the most deviant behaviors in biology.” (Olivia Judson 2002: 153)


In their best-selling book, Sex at Dawn, Chris Ryan and Cacilda Jethá suggest that there is a good amount of direct and circumstantial evidence that extended monogamy does not come easily for humans, and that this derives at least in part from our fairly promiscuous evolutionary history. (To clarify, they use the term ‘promiscuous’ not in a judgmental way, but merely to convey having multiple sex partners). Their main premise is that rigid monogamy became common only after our ancestors made the shift from hunting and gathering to agriculture. With agriculture came an emphasis on fixed settlements, private property that could be inherited, genetic paternity, and female sexual fidelity. They argue that this stands in contrast to our hunting-gathering past, when sexual relationships were more open and not confined to an exclusive pair-bond.

Bonobo sex. From Lola ya Bonobo

Bonobo sex. From Lola ya Bonobo


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Part 1. Humans are (Blank) -ogamous

(A)s our forebears adopted life on the dangerous ground, pair-bonding became imperative for females and practical for males. And monogamy – the human habit of forming a pair-bond with one individual at a time – evolved.” (Helen Fisher 2004: 131)

Several types of evidence suggest our pre-agricultural (prehistoric) ancestors lived in groups where most mature individuals would have had several ongoing sexual relationships at any given time. Though often casual, these relationships were not random or meaningless. Quite the opposite: they reinforced crucial social ties holding these highly interdependent communities together.” (Chris Ryan & Cacilda Jethá 2010: 9-10)

 “We are not a classic pair-bonded species. We are not a polygamous, tournament species either…. What we are, officially, … is a tragically confused species.” (Robert Sapolsky)



The above three quotations were selected to illustrate the range of views that exist on the evolution of human sexual and mating behavior. This is not a trivial matter. To primatologist Bernard Chapais: “The central puzzle of human social evolution… is to explain how promiscuity was replaced by the pair bond” (that is, assuming the pair-bond has gained complete ascendancy). But it’s about more than our ancestors’ mating behaviors. Lurking in the background is the notion that our ancestral behavioral patterns impact current ones, via phylogenetic inertia. Additionally, how we view the past is important because, rightly or wrongly, we have a tendency to associate what is natural with what is good (but note well the naturalistic fallacy). For both of these reasons, the past matters.

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