Vox has recently launched a series of short documentary films called Explained, to be released weekly on Netflix. The first episode, which can be found on YouTube, explores the issue of monogamy. The ideological thrust of the film is fairly clear: the concept of monogamous marriage is a recent and unnatural invention, and one that we as a society should probably grow out of sooner rather than later.
As it happens, I have no problem with this message. I fully support the right of consenting adults to organise themselves into whatever wacky sexual configurations they feel like. I wish every one of the carefully-selected rainbow of racially and sexually diverse couples giving their vox pops on the show nothing but happiness in their chosen lifestyles.
What I do have a problem with, however, is intellectual dishonesty. The film cites evidence from evolutionary biology and anthropology, no doubt intended to lend the whole affair an air of scientific credibility in the mind of a layperson. I would contend that the account that they give of the field is so selective and biased as to be seriously misleading.
Early on, the film explains the argument that differences in the sexual behaviour and attitudes of the two sexes evolved as a result of unequal parental investment. For a woman to reproduce takes considerable time and energy, which imposes a rather strict cap on the number of children a woman can potentially have. Men, on the other hand, can have a virtually infinite number of offspring, and thus have a strong evolutionary imperative to be “randy bastards”. So far, so good. This is an entirely mainstream, uncontroversial concept in the field of evolutionary psychology.
But wait! “There's one big issue with that explanation of promiscuous possessive men and demure women,” the narrator tells us. Cut to Christopher Ryan, author of Sex at Dawn. He informs us that hunter-gather societies, in which Homo sapiens lived for hundreds of thousands of years prior to the dawn of civilization, were “fiercely egalitarian”. The evolutionary psychologist Steven Pinker has written extensively on “the myth of the noble savage”: the persistent but, he argues, inaccurate view that our ancient ancestors enjoyed harmonious and just societal conditions. But even if, for the sake of argument, we grant this dubious premise, Ryan then makes the considerable leap that “there's no reason to think our ancestors shared everything except sexual partners”.
The film cites two examples of sexually permissive indigenous hunter-gatherer peoples that continued to exist into modern times. The first is an account by a Jesuit missionary of his conversation with a member of the Nazkapi (a Native American tribe) who reportedly said that “You French people love only your own children; but we all love all the children of our tribe”. In the face of all the serious anthropological literature that exists, the fact that the film-makers saw fit to include an anecdote from the 17th century is surely enough to ring some alarm bells. The second example is better: the Bari tribe of Venezuela, who practice “partible paternity”, i.e. the belief that all of a woman's sexual partners share the fatherhood of her child. This account of their society checks out, and it is fascinating, but this kind of de facto polyandry (one wife, many husbands) is so vanishingly rare that it can be considered the exception that proves the rule. (That rule would be polygyny, but more on that later.) As far as we know, partible paternity is largely confined to a handful of tribes in the Amazon basin, though the idea may have independently popped up in ancient Hawaii too.
The documentary now takes a sojourn into the animal kingdom, accurately pointing out that our two closest relatives, the chimpanzee and bonobo, have sexually promiscuous societies. They oversell the case by stating that “true monogamy is virtually unheard of the animal world”, a claim that is undercut a couple of minutes later when their own diagram of our closest evolutionary relatives correctly identifies gibbons as monogamous. Monogamy is indeed rare among animals, but by no means unheard of.
Back now to humans, and to the agricultural revolution that brought about the beginnings of civilization. Until now, the film would have the viewer believe, we had been happily having sex with whomsoever we pleased. But now that it had become possible to amass property and thus power, marriage was dreamed up as essentially a transactional arrangement to trade wealth and dominance between families and ultimately empires. (In actual fact, marriage appears on anthropologist Donald E Brown's list of human universals: it exists, in one form or another, in every human society ever studied.) This situation persisted, so the story goes, up until the 1700s, when Western civilization came up with the radical concept of marrying for romantic love.
What then follows is a bafflingly distorted account of the work of Charles Darwin. Historian Stephanie Coontz sets up the contrived narrative by arguing that the notion of marrying for love was a threat to the powers-that-were, so for some reason they had to push the idea that “men were aggressive and protective, women were nurturing and demure; they were opposites who complete each other”. “Male scientists” (it's worth watching the clip just to hear the narrator's tone, “male” is delivered almost as an epithet) like Darwin propped up this view, using “their theories... to explain Victorian gender roles”. The film quotes from Darwin's The Descent of Man (written in 1871, over a century after romantic, monogamous marriage had become commonplace in Europe): “Woman seems to differ from man in mental disposition, chiefly in her greater tenderness and less selfishness … [man] delights in competition, and this leads to ambition”.
I think what they are trying to do with this quotation is to paint Darwin as some stuffy old white guy with hopelessly outdated views. However, I would argue that this is a largely accurate description of the differences in average temperament between the sexes. Darwin was writing long before the development of the Big Five personality trait theory. One of the big five is Agreeableness, explained by Weisberg et al (2011) as follows: “Agreeableness comprises traits relating to altruism, such as empathy and kindness. Agreeableness involves the tendency toward cooperation, maintenance of social harmony, and consideration of the concerns of others (as opposed to exploitation or victimization of others). Women consistently score higher than men on Agreeableness and related measures”. So, just as Darwin's evolutionary theory predicted the existence of genes a century before the discovery of DNA, it predicted the results of psychometric personality tests long before these tests existed. Interestingly, sex differences in personality traits are “most pronounced in European and American cultures in which traditional sex roles are minimized” (Costa et al, 2001). Thus, Darwin's observations are even more true of 21st century Western culture than the Victorian society in which he lived!
The film then concludes with a mention of polyamory, suggesting that this might be the way of the future. So, the take home message is that our natural, pre-civilization state was one of free love, then monogamy was imposed upon us for ten thousand years or so by, I guess, the patriarchy, and now it's time to rethink that. However, the film-makers do not once mention polygamy, or more specifically, polygyny; a Martian watching this would have no idea that societies ever existed where a man took multiple wives. I appreciate that this is an 18-minute documentary, but still, this is a startling omission. It's as if they made a show about the Windows operating system and compared it to - I don't know – Haiku, without a word about MacOS.
The film describes our third-closest relatives, gorillas, as having a “promiscuous” society. In fact, high-status male gorillas have harems, with exclusive sexual access to several females. If we look at extant human hunter-gatherer societies, we see a mixture of lifelong monogamous marriage (either through courtship or arranged by others), serial monogamy (as one could argue is practiced today in Western culture), and polygyny. To give just a handful of examples, the Dogon of Mali, the Kipsigis of Kenya, the Xavante of Brazil, and the Yanomamo of Venezuela are polygynous. However, it's not until after the agricultural revolution that we see polygyny taken to extremes, with kings and emperors enjoying harems of hundreds or thousands of concubines. While the heyday of polygyny is behind us, polygynous marriages are still legally recognised in several African, Middle Eastern, and South Asian countries to this day. One wonders why they did not choose to include a Cameroonian or Pakistani man and his multiple wives in their vox pop lineup.
There is actually an interesting discussion to be had about the conditions that lead to a society being monogamous as opposed to polygynous. One can calculate how sexually egalitarian a society is by measuring the “reproductive skew”, which is the variance in the level of reproductive success between individuals of the population; think of the Gini coefficient, but for offspring. For the biological reasons discussed above, there tends to be greater variance for males than females. The highest male skews are found in polygynous societies: for men, there is a big gap between the sexual haves and have-nots. Modern European societies have among the lowest skews observed in the world (Brown et al, 2009). Viewed this way, monogamous marriage can be seen as a kind of sexual socialism for men.
Admittedly, this discussion is probably beyond the scope of an 18-minute documentary. Nevertheless, I think it's reasonable to hope that this film could act as a jumping off point, giving interested viewers the required background to explore issues like this further. Unfortunately, any layperson watching this would come away with a hopelessly distorted view of the field of evolutionary anthropology. Through dishonest cherry-picking and misrepresentation of the literature, this show has, in my view, completely failed in its titular mission: to explain. Rather, its purpose appears to be to persuade the viewers of the merits of a particular worldview.

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Great post! I think the importance of monogamous marriage to civilised societies is not adequately understood by most people. The frequent argument that non-monogamy is somehow more enlightened or better for society than monogamy is not supported by any evidence. Another thing to consider is the marriage premium - that married men earn more than comparable unmarried men, and the fact men are less likely to commit crimes when they are married.
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Thanks for the comment. I'd be wary of potentially confusing correlation with causation when it comes to the marriage premium though. While it's plausible that getting married makes men more law-abiding and productive, it seems just as likely that being law-abiding and productive makes a man more likely to find (and keep) a partner.
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