How Bonded Were Pairs?

As I said yesterday, the book Evolutionary Biology of Human Female Sexuality takes a standard view on human promiscuity:

Humans have been selected to pair bond, express mutual mate choice, and biparentally care for offspring. In these respects we appear to have diverged substantially from our closest phylogenetic relatives. [72] … Though in many species of nonhuman primates mating with multiple males to reduce their maltreatment of offspring has importantly selected for extended female sexuality, women’s extended sexuality probably does not significantly reflect this function. [77]

But in the range from near-perfect monogamy to chimp/bonobo style promiscuity, where do they think humans lie? Most of the book talks about how the signs of various effects suggest our ancestors had some “extra-pair mating,” but their only concrete indication of magnitudes is to describe the Hadza:

Hadza men spend much more time hunting large game than returns to their families warrant, which implies that male Hadza foragers do not … maximize gains through parental investment. So long as opportunities for mating with women other than currently primary partners are available to men … men should not be expected to allocate foraging time … [for] the fitness benefits of parental effort alone. …

Overall married Hadza women produce as many calories as do married Hadza men. … Women whose youngest children are 3 years of age or younger harvest about one-third fewer calories. And women with infants 1 year of age or younger harvest only about half as much. … Their husbands make up for the shortfall. [67]

So a Hadza man hunts big game to look sexy, even though that retrieves less food. Except that when a women he has sex with has a kid he thinks is his, he’ll gather more but less-sexy food, to give this woman ~1/2 of her food for one year, ~1/4 for the next two years, and declining amounts thereafter.

Now, yes, this may be more pair-bonding than in chimps or bonobos. But it is also far less than the farmer ideal of life-long monogamy!  Many men today reluctant to marry for life would be ok with this level of commitment. And of course we don’t know if Hadza levels of pair bonding were typical of our distant ancestors.

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  • rapscallion

    “But in the range from near-perfect monogamy to chimp/bonobo style promiscuity, where do they think humans lie?”

    Surely, the most relevant data for answering this question lies in current data on current humans, which is much less subject to error than speculative data on ancient humans. Nowadays, we see a lot of variation in human mating and pair-bonding behavior, so it’s clear that humans are capable of exhibiting a wide-range of behavior, spanning the entire spectrum from pure, austere monogamy to bacchanalia.

    I don’t think much of the idea that studying ancient behavior will tell us much about our true preferences. Observed, current behavior is the best way to study those. Even if ancient behavior differed radically from current behavior, it’s pure sophistry to label ancient behavior “human” and modern behavior somehow less-than-human. Human behavior is what humans do.

    Thinking of ancient behavior as somehow more authentic also invites bad faith rationalizations. People may think that higher ancient promiscuity means that cheating on their spouse is excusable since they’re just giving into their ancient biological drives. But knowing the origins of your biological urges doesn’t in fact make them any more or less compelling. If you are in a relationship and thinking of cheating, you already know all that’s relevant regarding how strong is the inducement to cheat; learning about the ancient origins of your urges doesn’t add any new, truly relevant information.

    • Well said. (If I had a “like” button I would have clicked it, but as it is I’m posting a whole comment instead just to say that.)

      • rapscallion


    • PJF

      Leaving aside the issue as to whether knowing the biological origins of one’s own urges should have any impact on the likelihood or otherwise of acting on those urges, it does seem that it might have an impact on how probable you consider it that, say, your partner might, or at the very least desire to, cheat on you.

    • Gil

      Wuss! The reason to think about ancient human behaviour is to get past current cultural impositions and find out what comes naturally. After all, the biological term “mate for life” means a when a boy critter and a girl critter pair up then they stay together for their duration of their lives. Should one die early then the other member will not pair up again regardless of his or her age. The fact that current societies still support multiple partners via serial monogamy shows that humans do not “mate for life”. The closest to monogamy for humans I heard of is the temporary pair-bonding long enough to get the child past infancy, i.e. four years of age. After that the relationship risks drifting apart as the chemical whirlwind dies down. There’s probably something to be said that couples with umpteen children stay together because of four years of serial spurts. However the fact human societies have traditionally been almost all polygynous until fairly recently says a lot that humans aren’t particularly genetically prone to monogamy.

      • Khoth

        It’s worth having another (somewhat hazy) datapoint, but don’t forget to take the ancient cultural impositions into account too.

      • Salem

        “The reason to think about ancient human behaviour is to get past current cultural impositions and find out what comes naturally.”

        As Khoth points out, ancient societies had cultures too. What makes you think ancient societies reflect anything other than cultural pressure to conform to forager norms? Given that foragers lived closer to starvation, can’t I argue that cultural pressures were stronger on foragers? After all, for foragers to deviate from norms will mean death, whereas farmers have more collective wiggle room. Hence the fact that we see a wide variety of cultural norms among different farming societies. I’m not saying I necessarily believe this, but the fact is that much of evo-psych is guesswork – unless you can provide hard evidence, one plausible-sounding narrative is as good as another.

        And not only that, but what makes culture an “imposition” and genetics “natural”? It’s an absurd divide.

        You calling rapscallion a wuss for his (excellent) post is of course typical, in that so many proponents of evo-psych come to it with an obvious axe to grind. The real reason to think about ancient human behaviour is better to understand ancient human behaviour. It may or may not tell us anything useful about modern humans.

  • Virtually Anonymous

    It is worth spending time at Peter Frost’s Evo and Proud blog to look at this question, because the answer depends.

    Firstly, there will be variation within each population group that has spent significant time being selected under specific conditions, and

    Secondly, different population groups will have mean values for preference for pair bonds that depend on the ability of females to provision their offspring by themselves (which is possible in some places) vs the requirement to have both parents contributing to offspring.

    • The front-page is currently full of posts about Cavali-Sforza. You might be referencing this post.

  • The second last paragraph reminds me of Veblen’s The Theory of the Leisure Class. He began from a different premise (hunting as high status, work as low status and so men did hunting because they don’t want to be associated with low status individuals) but the conclusion is about the same.

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