Life’s short, have you had an affair?

Today, millions of very nervous adults are furtively checking sites like “Have I been Pwned” to check if their account details at Ashley Madison have been leaked. Others are checking if their partners or acquaintances had accounts. The hacking and subsequent release of data from the world’s biggest infidelity-focussed dating service continues to reverberate, provoking an interesting suite of ethical questions.

Unless you’ve confined your news intake to re-runs of Jarryd Hayne’s BIG MOMENT in a trial game for the 49ers, you will be well aware that a group calling themselves Impact Team hacked the systems of Avid Life Media (ALM), who operate a number of sex and dating websites. Impact Team threatened to release sensitive information about users unless ALM close down Ashley Madison, which specialises in connecting people looking to have extra-relationship affairs, and Established Men, which they argue is a “website for rich men to pay for sex”. Established Men, understandably, puts it a little more gently: “connecting young, beautiful women with interesting men”.

Shhhhh! Ashley Madison screenshot.
Shhhhh! Ashley Madison screenshot.

So much for the libertarian hacker stereotype. Impact Team are waging a moralist crusade against both the websites themselves, and the people whose extra-marital or transactional sex shennanigans the websites enable.

Neither website has been shut down and yesterday Impact Team uploaded information about over 30 million users, including their email addresses. Security experts quoted in news outlets seem to agree that the data dump is genuine.

The media coverage has varied from titillating attempts to dissect where the “cheating” hotspots are to the very real personal stories of spouses who’ve been busted. Sydney radio station NOVA even tried, and rather spectacularly failed, to turn it into edgy commercial radio, searching the database on behalf of callers. They very quickly learned how spectacularly bad their idea was when they found the husband of one of their callers was indeed subscribed to Ashley Madison.

Nobody wins here. The whole business reeks of weakness and failure. As Gaby Hinsliff put it in the Guardian,

it’s hard to decide which of the activities involved – cyber blackmail, building a business on wrecking marriages, or just good old-fashioned philandering – is least charming.

More than gossip

But some people seem bouyed by the whole business. I’m intrigued by the level of schadenfreude; so many people are relishing the slow implosion of Ashley Madison and the exposure of millions of people’s most embarrassing intimate details. What disappoints me most is how the exposure of 30 million people is being shoe-horned into a one-size-fits-all view of sex and relationships. How this is all about “cheating”, and that infidelity means the same thing in every relationship.

We might not like to admit it to ourselves, but relationships differ enormously from one another. So do the reasons people have sex, both within and outside of committed relationships. Yes, a great many – probably most – Ashley Madison clients were furtively seeking extra sexual partners without the knowledge and consent of their long-term partners. And many did so despite their relationships being otherwise functional, productive and respectful. This kind of infidelity has its victims: the partners who remain at home, pouring their selves into the shared enterprise of coupledom, unaware that the other party isn’t matching their effort and commitment.

According to Leonard Cohen (Live in London), “Everybody Knows that you’ve been faithful. Give or take a night or two”.

And yet nobody can properly evaluate another’s relationship from outside, much less 30 million relationships. The evolutionary sciences continue to show that humans have a marvellous capacity to form loving, cooperative relationships, to remain sexually faithful to one another, and to work hard to build both families and wealth. Marvellous as those relationships can be, profound as the love that binds us together might feel, not all relationships remain functional.

One of the less-explored dimensions of the Ashley Madison schamozzle is the fact that many people had quite defensible positions for looking outside their relationships. Their current relationships might be loveless, sexless, dysfunctional, exploitative or even abusive. They may be in the process of coming out to themselves, facing the daily dissonance of being gay in a straight marriage.

A great many people are trapped by economic circumstances and questions of child custody in hellish relationships. Who would deny those people the chance to connect with another, perhaps to find the courage or even the ally they need to escape, or perhaps to enjoy being loved, appreciated and getting properly laid?

How many people, whose names appeared on that database last night, had to go home to their controlling, jealous, or abusive partners? How many people, living straight lives, many in countries where homosexuality is illegal and harshly punished, were outed by Impact Team’s self-righteous moralism?

Beyond the many dysfunctional relationships from which affairs might offer respite or escape, the Ashley Madison affair forces us to confront even more uncomfortable realities about relationships. Even “a mommy and daddy who love each other very much” are likely to find that they cannot be everything one another needs. Our evolved capacity to be really quite good at monogamy has its limits. We have also evolved, thanks to our ancestors’ tastes for sexual intrigue, an exquisitely context-dependent capacity to throw off the shackles of monogamy when it suits us. It takes a spectacular denial of human nature to believe that life-long heterosexual monogamy represents some kind of social zenith and that deviations from this one true path represent deep aberrations.

On-line dating has imposed what economists call a “technological shock” on the mating market, reshaping how people meet, court and, ultimately, mate. Ashley Madison’s success, and the marketing genius behind it’s quasi-inspirational slogan (“Life’s short. Have an affair.”), reshaped the extra-couple mating market. And the realisation to which so many customers are waking today, that even a website set up to guarantee discretion in extracurricular hooking up is vulnerable to hacking and public shaming, will change the dynamics of sex once again.

I would be disappointed if the whole business turns into a witchhunt on “cheaters”, if we slide back toward the puritanism that had Hester Prynne wearing the Scarlet Letter. Perhaps we need to embrace the messier, more complex reality that sex does not equal love, and love does not always mean exclusively and forever. Our relationships are negotiated every day in the way we treat one another and accept our partners, and lovers, as they are, rather than packing them into the neat box of a one-size-fits-all relationship.

The Conversation

Rob Brooks is Scientia Professor of Evolutionary Ecology; Director, Evolution & Ecology Research Centre at UNSW Australia

This article was originally published on The Conversation. Read the original article.

Early bird gets the sperm … to the egg

What gets you out of bed in the morning? Before morning has broken, and some time before blackbird has spoken, songbirds rise for sex. And a clever new experiment reveals just how important it is for male songbirds not to sleep in.

A great many species of songbirds nest in pairs, presenting to the world a facade of monogamy. Until the 1990’s, songbirds were rhapsodised by social conservatives as paragons of family values, mother and father working together faithfully to fledge their demanding chicks. Until new genetic technologies revealed that most socially monogamous birds were playing a lot of away games.

For a long time, ornithologists failed to spot the shennaniganising because most of it happens just before dawn, when even the hardiest birdo is still rubbing sleep from their eyes. That’s actually a bit unfair: ANU’s Professor Andrew Cockburn and his many collaborators have risen unspeakably early for decades to study Australia’s superb fairy wrens, revealing them to be Olympic medallists of extra-pair sex. Female wrens leave the nest before dawn, heading straight to males singing in the dawn chorus.

This kind of behaviour gives male birds two reasons to rise early: to prevent their social mate from mating with another male, and perhaps to get a little bit on the side from some other male’s social mate. European blue tit males who start singing early in the morning sire more chicks with other females, chicks he doesn’t have to raise because the female and her social mate do all the heavy lifting.

No wonder those Three Little Birds were cheerful when Bob Marley rose and smiled with the rising sun!

Consequences

But how do early and late risers do with their social mates? A team based at the Max Planck Institute for Ornithology in Radolfzell, Germany, found an ingenious way to answer this question.

By inserting slow-release melatonin implants beneath the skin of free-living male Great Tits, just before the breeding season, they tweaked the birds’ circadian rhythms. The body releases the hormone melatonin at night, and animal circadian activity patterns are cued by melatonin levels. Nocturnal animals are stirred into activity and dirurnal animals to sleep by rising melatonin.

Early rising male Great Tits can get the sexy stuff over with and spend the res of the day looking fabulous. Israel Gutiérrez/flickr
Early rising male Great Tits can get the sexy stuff over with and spend the res of the day looking fabulous. Israel Gutiérrez/flickr

Male great tits in the control group became active about 22 minutes before dawn, but those with melatonin implants took an extra ten minutes to get going. They were no less active during the day, and they stopped for the night at the same time, a few minutes before dusk.

But those extra ten minutes cost the males dearly. Twelve percent of chicks fledged from the nests of control males were sired by another male, but 42 percent of chicks in the nests of melatonin-implanted males had been conceived with another male’s sperm.

As an early riser, I’d like to claim victory for the early birds at this point. But of course I can’t. For humans, Sex at Dawn remains niche. Many even prefer to rise early for bird watching.

The night time is where the action is for our species. Night owls tend to be more extrovert, novelty-seeking, and night-owl men (but not women) report having more sexual partners. Night-owls are more likely than early risers to be single and open to short-term commitment-free sex. Being a night owl is associated with risk-taking in women on a levels similar to males (both night-owls and early risers). Risk-taking predicts short-term sexual behaviour, suggesting that female night owls might be especially oriented toward sex.

Interesting, it’s true, but not yet the basis for any firm prescriptions. Unless you’re Charlotte Alter writing at Time Magazine. Anybody spot the implicit bias and rampant earlybirdophobia?

Women who stay up late are more likely to get laid, but less likely to get married than women who get up early to do a sun salutation or whatever.

Whatever indeed!

Up all night to get lucky? Thank you Daft Punk!

The Conversation

Rob Brooks is Scientia Professor of Evolutionary Ecology; Director, Evolution & Ecology Research Centre at UNSW Australia

This article was originally published on The Conversation. Read the original article.

Violence: blaming the bloke but not the booze

“Spoiling for a Bar Fight” Jonathan Cohen/Flickr, CC BY-NC
“Spoiling for a Bar Fight” Jonathan Cohen/Flickr, CC BY-NC

Is alcohol-fuelled violence caused by the booze itself or by the macho culture in which the drinking occurs? If we are to believe a recent study commissioned by the alcohol company Lion, it’s the culture that’s to blame. That’s a rather convenient conclusion for the alcohol industry. But it hinges on a fallacy and has the potential to cause much damage.

The study was conducted by Dr Anne Fox, consultant anthropologist and founding director of Galahad SMS Ltd (SMS stands for Substance Misuse Solutions) who studies drinking cultures. Fox has been promoting her report in the broadcast media and op-eds, pushing her conclusion that

It is the wider culture that determines behaviour while drinking, not the drinking per se. While there are very good health reasons to reduce excessive drinking, you must influence culture if you want to change behaviour.

The Lion and the Fox

Fox’s report reads as a series of anecdotes and quotes, gathered during discussions with drinkers in a variety of situations, workers in bars, taxi drivers, police, emergency workers, government officials and various other people. Fox’s observations are organised thematically, interspersed with folk-evolutionary speculation of the following kind:

Could ritualised drunken behaviour be a re-enaction of an evolved ancient need for joyous bonding that still persists? Given what we know about alcohol and the brain, and the evolution of the brain itself, the question can at least be asked.

And simplistic characterisations of national drinking cultures, such as:

Spaniards and Italians … are culturally much more emotionally extroverted and do not associate alcohol so much with romantic or sentimental expression.

There is no attempt to grapple with numbers surrounding violence, or the consumption of alcohol. In fact there seems to be no way of sifting evidence with any kind of fairness to the competing alternatives at all. Instead, as might be expected when a liquor company commissions an expert on ‘drinking culture’ to study what causes the violence that too-often erupts in and around venues where alcohol is served, the conclusions seems inevitable: you have to change the culture in which the alcohol is consumed.

And which aspects of culture are most in need of changing? Why, masculinity, of course. As Fox put it in the Sydney Morning Herald:

The way to tackle the real underlying causes of anti-social behaviour is to address the cultural reinforcers of violence, misogyny, and aggressive masculinity in all its cultural expressions from schoolyards to sports fields, politics and pubs, movies and media.

Who better to tie together alcohol, misogyny and high culture then Snoop Dogg? Gin and Juice (1993)

Could it work?

The Fox/Lion report reminds me of nothing more than the American gun lobby slogan that “Guns don’t kill people. People kill people”. By reducing the complex issues of gun-related homicide to two apparently contradictory alternatives, those most wedded to their right to bear arms find rhetorical – if not logical – comfort in blaming the shooter and not the weapon.

Having read the report, I think there are interesting observations about the relationships that Australians and New Zealanders have with alcohol, well worth injecting into the national debate on antisocial behaviour. But should we leap from observing that culture is important to focusing all interventions on the remodelling Austral masculinity? I’m sure the liquor lobby would like to do so, but I’m not the only one who disagrees.

Deakin’s Peter Miller has already published an excellent Fact Check on the Fox/Lion report, concluding:

It’s not correct to say you can’t “alter the culture of violence and anti-social behaviour in any meaningful way” by tackling the way people drink. There is a lot of evidence showing that changing people’s drinking hours and consumption patterns reduces violence and hospital admissions – which is a lot more significant than tinkering at the margins of culture.

Cultural creationist wishful thinking

It seems that those who study ‘culture’, that slippery omnipresence in which we all wallow, inevitably conclude that the only way to improve society is to change culture. Drain the toxically misogynist, masculine swamp, and replace it with a more rarified egalitarian pond, and everything will be okay.

Changing ‘culture’ isn’t easy. And it certainly amounts to far more than education campaigns, shaming and punishing bad behaviour.

Fox, to her credit, doesn’t insist on throwing out all biological insights. She recognises that night-time drinking among young people is about meeting evolved biological needs, for bonding, belonging and courtship. And that young men competing with men, and seeking to impress women are the well-spring of most of the anti-social behaviour.

Her report considers the example of Icelanders who consume more booze and own more guns, but do far fewer stupid, violent things per capita than Australians. She even recognises that Iceland’s low-levels of economic inequality remove some of the incentives for young men to pose, to impress, and to take out the competition.

If Australia wants to “change the culture” in which drinking takes place, it will have to change more than arbitrary social sanctions and “culturally constructed” ideas of what it means to be a manly man. If that is even possible. It will have to recognise that economic conditions, create the incentives for young men to strive, to compete and to take stupid risks.

And that means resisting the temptation to blame single causes. It isn’t just the booze, it isn’t just the blokes, it isn’t just the economy and it certainly isn’t just the culture. What matters is how those ingredients combine.

Perhaps we need to look more closely at the incentives for young men to strive and take risks. Eminem captures this in “Lose Yourself”.

The Conversation

Rob Brooks is Scientia Professor of Evolutionary Ecology; Director, Evolution & Ecology Research Centre at UNSW Australia

This article was originally published on The Conversation. Read the original article.

Is there really a single ideal body shape for women?

Boticelli's "Birth of Venus" c. 1486.
Boticelli’s “Birth of Venus” c. 1486.

Many scholars of Renaissance art tell us that Botticelli’s Birth of Venus captures the tension between the celestial perfection of divine beauty and its flawed earthly manifestation. As classical ideas blossomed anew in 15th-century Florence, Botticelli could not have missed the popular Neoplatonic notion that contemplating earthly beauty teaches us about the divine.

Evolutionary biologists aren’t all that Neoplatonic. Like most scientists, we’ve long stopped contemplating the celestial, having – to appropriate Laplace’s immortal words to Napoleon – “no need of that hypothesis”. It is the messy imperfection of the real world that interests us on its own terms.

My own speciality concerns the messy conflicts that inhere to love, sex and beauty. Attempts to cultivate a simple understanding of beauty – one that can fill a 200-word magazine ad promoting age-reversing snake oil, for example – tend to consistently come up short.

Waist to hip

Nowhere does the barren distinction between biology and culture grow more physically obvious than in the discussion of women’s body shapes and attractiveness. The biological study of body shape has, for two decades, been preoccupied with the ratio of waist to hip circumference.

With clever experimental manipulations of line drawings, Devendra Singh famously demonstrated that images of women with waists 70% as big as their hips tend to be most attractive. This 0.7:1 waist-to-hip ratio (WHR), it turns out, also reflects a distribution of abdominal fat associated with good health and fertility.

Singh also showed that Miss America pageant winners and Playboy playmates tended to have a WHR of 0.7 despite changes in the general slenderness of these two samples of women thought to embody American beauty ideals.

Singh’s experiments were repeated in a variety of countries and societies that differ in both average body shape and apparent ideals. The results weren’t unanimous, but a waist-to-hip ratio of 0.7 came up as most attractive more often than not. The idea of an optimal ratio is so appealing in its simplicity that it became a staple factoid for magazines such as Cosmo.

There’s plenty to argue about with waist-hip ratio research. Some researchers have found that other indices, like Body Mass Index (BMI) explain body attractiveness more effectively.

But others reject the reductionism of measures like WHR and BMI altogether. This rejection reaches its extremes in the notion that ideas of body attractiveness are entirely culturally constructed and arbitrary. Or, more sinisterly, designed by our capitalist overlords in the diet industry to be inherently unattainable.

The evidence? The observation that women’s bodies differ, on average, between places or times. That’s the idea animating the following video, long on production values, short on scholarship and truly astronomic on the number of hits (21 million-plus at the time of writing):

This rather questionable video, called ‘Women’s Ideal Body Types Throughout History’, is getting a lot of airplay on YouTube.

I note that Botticelli’s Venus looks more at home in the 20th Century than among the more full-figured Renaissance “ideals”. So do the Goddesses and Graces in La Primavera. Perhaps there was room for more than one kind of attractive body in the Florentine Renaissance? Or is the relationship between attractiveness and body shape less changeable and more variegated than videos like the one above would have us believe?

Not that I’m down on body shape diversity. Despite the fact that there seems to be only one way to make a supermodel, real women differ dramatically and quite different body types can be equally attractive. The science of attractiveness must grapple with variation, both within societies and among cultures.

Enter the BodyLab

For some years our research group has wrestled with exactly these issues, and with the fact that bodies vary in so many more dimensions than just their waists and their hips. To that end, we established the BodyLab project, a “digital ecosystem” in which people from all over the internet rate the attractiveness of curious-looking bodies like the male example below.

Example image from the BodyLab ‘digital ecosystem’. The VW Beetle is provided as the universal symbol of something-slightly-shorter-than-an-adult-human. Faces pixellated to preserve any grey people’s anonymity. Rob Brooks/BodyLab.biz
Example image from the BodyLab ‘digital ecosystem’. The VW Beetle is provided as the universal symbol of something-slightly-shorter-than-an-adult-human. Faces pixellated to preserve any grey people’s anonymity.
Rob Brooks/BodyLab.biz

We call it a “digital ecosystem” not to maximise pretentiousness, but because this experiment involved multiple generations of selection and evolution. We started with measurements of 20 American women, a sample representing a wide variety of body shapes.

We then “mutated” those measures, adding or subtracting small amounts of random variation to each of 24 traits. Taking these newly mutated measures we built digital bodies, giving them an attractive middle-grey skin tone in an attempt to keep variation in skin colour, texture etc out of the already complex story.

If you want to help out with our second study, on male bodies, visit BodyLab and click through to Body Shape Study and then Rate Males (Generation 6).

This all involved considerable technologic innovation, resulting in an experiment unlike any other. We had a population of bodies (120 per generation) that we could select after a few thousand people had rated them for attractiveness. We then “bred” from the most attractive half of all models and released the new generation into the digital ecosystem.

What did we find? In a paper just published at Evolution & Human Behavior, the most dramatic result was that the average model became more slender with each generation. Almost every measure of girth decreased dramatically, whereas legs and arms evolved to be longer.

In eight generations, the average body became more slender. Waist, seat, collar, bust, underbust, forearm, bicep, calf and thigh girth all decreased by more than one standard deviation. At the same time, leg length (inseam) rose by 1.4 standard deviations. Rob Brooks
In eight generations, the average body became more slender. Waist, seat, collar, bust, underbust, forearm, bicep, calf and thigh girth all decreased by more than one standard deviation. At the same time, leg length (inseam) rose by 1.4 standard deviations.
Rob Brooks

That may not seem surprising, particularly because the families “bred” from the most overweight individuals at the start of the experiment were eliminated in the first few generations.

But, after that, more families remained in the digital ecosystem, surviving generation after generation of selection, than we would have expected if there was a single most attractive body type. The Darwinian process we imposed on our bodies had started acting on the mutations we added during the breeding process.

More meaningful than the mean

Those “mutations” that we introduced allowed bodies to evolve free from all the developmental constraints that apply to real-world bodies. For example, leg lengths could evolve independently of arm lengths. Waists could get smaller even as thighs got bigger.

When we examined those five families that lasted longest as our digital ecosystem evolved, we observed a couple of interesting nuances.

First, selection targeted waist size itself, rather than waist-hip ratio. No statistical model involving hip size (either on its own or in waist-hip ratio) could come close to explaining attractiveness as well as waist size alone. Our subjects liked the look of slender models with especially slender waists. There was nothing magical about a 0.7 waist-to-hip ratio.

Second, within attractive families, which were the more slender families to begin with, evolution bucked the population-wide trend. These bodies began evolving to be more shapely, with bigger busts and more substantial curves.

It turns out there’s more than one way to make an attractive body, and those different body types evolve to be well-integrated. That’s a liberating message for most of us: evolutionary biology has more to offer our understanding of diversity than the idea that only one “most attractive” body (or face, or personality) always wins out.

What about the cultural constructionists? Are body ideals arbitrary, or tools of the patriarchal-commercial complex?

Our results suggest that the similarities between places, and even between male and female raters, are pretty strong: the 60,000 or so people who viewed and rated our images held broadly similar ideas of what was hot and what was not. But their tastes weren’t uniform. We think most individuals could see beauty in variety, if not in the full scope of diversity on offer.

What’s cool about our evolving bodies, however, is that we can run the experiment again and again. We can do so with different groups of subjects, or even using the same subjects before and after they’ve experienced some kind of intervention (perhaps body-image consciousness-raising?). I’m hoping we can use them to look, in unprecedented depth, at the intricate ways in which experience, culture and biology interact.

The Conversation

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Sexually despotic men rewrite history

Alfred L. Kroeber (left) with Ishi, the last member of California’s Yahi people, in 1911. Wikimedia Commons
Alfred L. Kroeber (left) with Ishi, the last member of California’s Yahi people, in 1911. Wikimedia Commons

“Heredity”, opined the pioneering cultural anthropologist Alfred L. Kroeber in 1915, “cannot be allowed to have acted any part in history”. I have yet to encounter a crisper expression of the view that biological explanations have no place in the study of society and history. Kroeber’s words have resonated through the social sciences for a century, divorcing nurture from nature, social from biological, at considerable harm to our understanding of society and what it means to be human.

 

Fortunately, many 21st Century anthropologists, economists, neuroscientists, geneticists, sociologists and thinkers so busily inter-disciplinary that they defy dusty departmental labels, are consigning the hoary distinction between nature and nurture to the past. Likewise the distinction between heredity and history is steadily dissolving as the where intimate links between evolutionary fitness and major historic transitions come into view.

Last week’s European Journal of Human Genetics, for example, carried a fascinating article led by evolutionary geneticist Patricia Balaresque exploring the signature of historic population expansions in the distribution of Y-chromosome genotypes of men alive today.

The Y of who, what and when

The the human Y chromosome represents a tiny portion of the genome, including the genes that trigger a foetus to develop into a male, rather than following the default female pathway. Every now and then a small change occurs in one of the less important parts of a Y-chromosome’s DNA. Such a change is passed to a man’s sons, those sons’ sons, and so on. That means there’s quite a bit of variation in these Y-chromosome sequences in any human population.

Marco Polo at the Kublai Khan. Miniature from the Travels of Marco Polo c 1298.
Marco Polo at the Kublai Khan. Miniature from the Travels of Marco Polo c 1298.

So if a man happens to have many sons, who each go on to have many sons and so on, one might detect a sudden surge in the frequency of the Y-chromosome sequence borne by that line of men (patriline). In 2003, a large team from Oxford University detected evidence of just such an event. Across much of Asia, one particular Y-chromosome sequence was carried by 8 percent of all men. In a paper pithily titled “The Genetic Legacy of the Mongols”, they famously fingered Genghis Khan as the chief suspect.

The pattern of variation within the lineage suggested that it originated in Mongolia approximately 1,000 years ago. Such a rapid spread cannot have occurred by chance; it must have been a result of selection. The lineage is carried by likely male-line descendants of Genghis Khan, and we therefore propose that it has spread by a novel form of social selection resulting from their behavior.

Where by ‘behaviour’ they mean more than the Great Khan’s triumph in unifying the Mongols and establishing the largest continuous empire history has ever known. For Khan was as much about the establishment of a genetic dynasty as a political one. According to one disputed quote, he once said:

The greatest joy for a man is to defeat his enemies, to drive them before him, to take from them all they possess, to see those they love in tears, to ride their horses, and to hold their wives and daughters in his arms.

Or words to that effect.

Such a genetic legacy is far more than the work of a single man. It is likely that Khan’s uncles, brothers and cousins, played a substantial role, too. And his direct male descendants spread both his empire and his genetic legacy. Ghenghis’ grandson, Kublai Khan, married four main Empresses, but, according to Marco Polo’s Travels was attended to by hundreds of beautiful young women, working five at a time in three-day shifts. And a much greater number of women, recruited to the palace but, after a second round of screening, not deemed perfect enough for the Khan himself, were bestowed on Kublai’s nobles, many of whom would have been relatives sharing his patriline and Y-chromosome.

Khan not the only one

The Mongol expansion is far from the only such event to leave a genetic signature. A 2005 paper identified a particularly successful lineage that expanded about 500 years ago in Northeastern China, possibly through the lineage who established the Quing Dynasty.

Last week’s findings report on a survey of 5321 men from 127 Asian populations, testing for evidence of similar population expansions. Belaresque and her collaborators identified eleven such events, including the ones tied to the expansions of the Mongols and the Qing dynasty. And some of those events date back as far as 2100 BCE.

The earliest expansions, between 2100 and 300 BCE, are associated with the flourishing of agriculture in the Fertile Crescent, East India, and South East Asia. As agriculture took hold, elites accumulated wealth and influence beyond anything our hunter-gatherer ancestors could have conceived. These represent perfect conditions for sexual despots: male rulers who take many wives, keep numerous concubines or mistresses, and have many offspring. They also establish successions that favour their male descendants, handing them the wealth and power to become sexual despots themselves.

Another expansion began around 1100 CE in the Near East and expanded to the South East Indian coast. This might be a signature of the “rapid expansion of Muslim power … after the establishment of a unified polity in the Arabian peninsula by Muhammad in the 7th Century and under the subsequent Caliphates”.

The Mongol and Qing expansions, and another from Northeast China beginning no earlier than 850 CE, were not associated with the establishment and spread of agriculture, but rather with nomadic, pastoral lifestyles made possible by the domestication of horses. Pastoral nomads ruled the steppes for thousands of years, thanks to their horse-powered mobility and fighting ability.

They established several empires, giving rise to hierarchies, elites and patrilineal reproductive despots like the Khans and the Qing. And their Silk Road trade corridor facilitated westward expansion of their genetic dynasties.

Heredity and History

Even in the rather well-studied case of Genghis Khan we are well beyond certain idenfification of the individual progenitors whose success sparked each expansion. Innovative analyses and lucky ancient DNA finds may yet do so for some cases. But the ability to detect great tides of patrilineal descent in societies of various types offers far more interesting possibilities than compelling personal narrative.

The evidence shows that with great power and wealth can come great evolutionary fitness. The tools are now falling into place to assess how much the psychological adaptations that shape reproductive success have given history its shape.

This is one tale where History certainly represents HIS Story. The fact that new Y chromosome sequences can spread so fast and so wide when history’s tide turns suggests that a very small number of sexually despotic men can leave massive numbers of descendants. But each man who traces his descent back to Genghis Khan or another such super-ancestor through an unbroken male line has sisters who do so too, save for the very last branch in their family tree. If 2% of people in Asia descend on a male-only lineage from the same male ancestor as Khan, then how many times do they descend from him through at least one female ancesor?

Each of us descends many times over from a great many sexual despots. It would be Kroeber-like wilful ignorance to be think we don’t also inherit many of the genes that biased their behaviour toward the accumulation of power, the vanquishing of rivals and reproductive despotism.

And when I say “we”, I don’t only mean men. Every man has a mother. Every descendant of Ghenghis Khan is also a descendant of his mother Hoelun.

The Conversation

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Fred dives, Neymar scores, Brazil wins! Straight out of the textbook

The soccer World Cup (yes, I persist in calling it “soccer”) is the one time in every four years I pay any sustained attention to the round-ball game. There is so much to love about the world’s most popular sport, played by its best players, with fanatical but mostly benign national supporters.

And yet by tournaments’ end I cannot bear to watch another dive, any more theatrical writhing on the ground or another posse of 20-something millionaires heatedly admonishing an official. Perhaps it’s something in the water at my place or a consequence of being thrashed too frequently in high school, but I prefer the stoic deference to authority of rugby union, in which backchatting the referee automatically moves the penalty 10m closer to your goal line.

So, with all the bright-eyed hope in the world game, I rose this morning at six to watch Brazil’s inevitable dismantling of Croatia. But Croatia’s Portuguese interpreter clearly couldn’t understand the memo, written as it was in Português do Brasil. Unaware they were supposed to be dismantled, they had the temerity to go ahead in the 11th minute.

A cracking contest, then, made even when Neymar slipped one just inside the Croatian post in the 29th minute. Very little remonstrating, some robust challenges but not too much play-acting, and very few dives. Until the 71st minute.

This is why soccer players dive. “Scientifically proven” as they say in pseudoscientific advertisements for fast-moving consumer goods. In this case, Fred’s dive fits perfectly with a scientific analysis of soccer diving by Gwendolyn David in 2011 and a team of collaborators at the University of Queensland.

In order to understand the dynamics of who dives and when, David viewed 2,800 falls in 60 matches of soccer across 10 professional leagues. David’s PhD supervisor and collaborator on the paper, Robbie Wilson, and Amanda Niehaus wrote about the paper’s findings and implications for The Conversation when the paper was published. As they put it:

It turns out that diving is more common when there’s more to gain by it: in the offensive half of the field – specifically, in or near the penalty box – and when scores between the teams are tied.

That’s exactly what happened this morning. Fred dived in a part of the field where he had everything to gain and almost nothing to lose. And it isn’t just Croatian supporters who thought the decision to award a penalty – the penalty that broke the tie – diminished an exciting game of football.

I’ll probably get up most mornings to watch the games, but I’d rather see referees take a harsher line on the theatrics. Like those zero-tolerance rugby referees, I’m pretty sure a few more yellow cards would tone down the histrionics and improve the overall spectacle. In fact David’s analysis shows that in leagues where refs are tough on diving, players do it less often.

My daughter was born the night John Aloisi scored that goal to put Australia through to compete in Germany 2006. And all Australian supporters know where that campaign ended up. Two words: Fabio Grosso.

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What are the chances that your dad isn’t your father?

How confident are you that the man you call dad is really your biological father? If you believe some of the most commonly-quoted figures, you could be forgiven for not being very confident at all. But how accurate are those figures?

Questions of paternity are built over the deepest well of human insecurity, for children searching to know who they are, for fathers wanting to know whose kids they are raising and for mothers uncertain about the strength of the bonds holding their families together.

I consulted on an episode of SBS’s Tales of the Unexpected documentary series, “Who’s Your Daddy?” (screening this Sunday April 20) which looks at the issue in some detail.

The program explores the question of paternity certainty, combining three moving tales – each involving a DNA paternity test – with a poll of sexual behaviour in Australia and the US and an exposition of why uncertain paternity presents such a sensitive issue.

One of the three?

How many children are the genetic offspring of someone other than the guy who thinks he is the father?

 

If you have read, heard or watched anything on this question, you will have encountered many estimates, from 9% to more than 30%. The idea that almost one in three people might be the result of what we biologists rather matter-of-factly call “extra-pair copulations” titillates and horrifies in equal measure.

These estimates surprise most people when they first hear them. So much so that the numbers tend to stick in our minds. But do these numbers bear any truth?

The problem with most data on paternity is the near impossibility of obtaining an unbiased sample. A paternity clinic, for example, is a bad place from which to estimate the rate of misattributed paternity. Many clients are there because at least one party isn’t convinced.

Likewise, any study recruiting families – however randomly – might have more success recruiting mothers who harbour no doubts about their children’s paternity.

Questionable figures

Swinburne University sociologist Michael Gilding, who also appears in the SBS program, has thoroughly researched the origins of the popular belief that 10% to 30% of paternities are misattributed.

He traced the source of the high estimate – 30% – to the transcript of a symposium held in 1972 in which British gynaecologist and obstetrician Dr Elliot Philipp mentioned an estimate from a small sample of parents.

This brief conversation took on a life of its own, despite the fact that Dr Philipp never published the findings of his study. As a result, his precise tests and his population sample were never identified.

Of the many studies that have attempted to estimate the rate of misattributed paternity, the higher estimates have tended to grab headlines, whereas more modest estimates sink without trace.

In whose interest?

Prof Gilding implicates two groups for inflating the public perception of misattributed paternity rates: evolutionary psychologists and fathers’ rights groups.

Evolutionary psychologists, according to Gilding, are so invested in their ideas about the nuanced mating decisions women make that they overestimate how often women mate outside their long-term relationships. My impression is that this may be an accurate assessment of some headline-grabbing research but not universally true of the field.

Fathers’ rights groups represent men negotiating the heartbreak of family break-up. Some such groups also host strident activists propelled by a conviction that the law and society have been utterly corrupted by feminism, gynocentrism and misandry.

The blogs and forums of this netherworld amplify any finding, however flimsy, implying that women are rampantly promiscuous or cynical swindlers looking to part men from their hard-earned cash or dupe them into caring for kids that don’t bear their DNA.

They call this “paternity fraud” and some claim it “worse than rape”.

You won’t find on their websites a critical analysis of the sampling methods or techniques used to estimate paternity misattribution rates, just titanium-reinforced convictions that 25% to 30% of children are being raised or supported by the “wrong” guy.

Why does it matter?

In the ever-dynamic game of sexual relations, the one factor that has always weighed decisively in the favour of womankind is the secure knowledge that she is the mother of her children. According to an old aphorism: “Maternity is a matter of fact, whereas paternity is a matter of opinion.” At least it used to be.

Paternity testing now much easier and cheaper.

Fast-moving developments in molecular biology make paternity testing faster, cheaper and more accurate than ever before. Analysis of foetal DNA in the mother’s blood enable paternity assignment as early as eight weeks into a pregnancy.

Interweaving strands of evolutionary research suggests that paternity confidence forms part of the glue bonding men to their children and to the women who bore them. Undermine that confidence and men invest less readily in the subsistence and safety of their families, and become more likely to abscond.

That is not to say that all men are calculating Darwinian cynics. Many men make magnificent fathers to children that do not bear their DNA. But men get immoderately touchy about paternity. Insecurity over paternity has tectonically shaped much that is least admirable about male behaviour and twisted societies.

But knowledge about paternity can be empowering. It can reassure an uncertain father. It can vindicate an impugned mother or assist her in a paternity suit. And it can help a child understand who they are and where they come from.

What’s the answer?

So how many children are sired by someone other than “Dad”?

Population-wide random-sample DNA testing remains financially and ethically unviable. But to understand some of the behaviours that might lead to paternity misattribution, the SBS documentary producers commissioned Roy Morgan Research to poll samples of Australian and American women.

They asked a number of questions including whether they had conceived a child at a time when they had multiple sexual partners? I was surprised that no more than 2% of women admitted to this.

That suggests a low rate of misattributed paternity; but note the data are presented per woman, not per child. The poll does suggest that mating with multiple men around the time of conception is neither rampant nor pathologically rare.

These results marry comfortably with DNA estimates of misattributed paternity from samples that cross a broad range of societies which suggest the rate is between 1% and 3%, and with Prof Gilding’s estimate of between 0.7% and 2%.

The number of children whose biological father isn’t their social dad is probably far smaller than you’ve been led to believe, although the 30% figure seems to be a zombie-statistic that refuses to die.

But even a 1% rate of misattributed paternity still adds up to millions of individual children, world-wide, each part of an interesting, sometimes tenuous and often heart-breaking story.

The Conversation

Rob Brooks receives funding from the Australian Research Council. He consulted, without remuneration, with the production company (Cordell Jigsaw Zapruder) on the design of the paternity poll and the content of the show, and appears in the program mentioned here.

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Fear not the hipster beard: it too shall pass

If you haven’t been outdoors in a few years, you might not have noticed that beards are back. Back in such a big way that apparently many New York hipsters are paying north of US$8,000 for “facial hair transplants” to embellish their patchy beards.

While the hipster subculture appears to be ground zero for the latest swerve toward beardedness, men who would not be seen dead in skinny jeans or thrift-shop cardigans are letting the whiskers grow in a way that hasn’t been fashionable for decades.

Why are beards sprouting from the unlikeliest faces? And is there anything that might make them stop?

The advantage of rarity

Today in Biology Letters we provide experimental insights into why beard fashions come and go, and why there is no single optimum pattern of facial hair. By we, I mean my former Honours student Zinnia Janif, my colleague and Zinnia’s co-supervisor Dr Barnaby Dixson and me.

We speculated that a phenomenon called “negative frequency dependence” (NFD) might help explain diversity in facial hair patterns. Negative frequency dependence simply means that rare traits enjoy an advantage.

In evolutionary genetics, NFD selection is an important force, favouring rare genetic alleles over more common ones. In guppies, for example, males bearing rare combinations of coloured spots are both less likely to be preyed on and more likely to gain matings in the wild. So a rare colour pattern can spread very rapidly until it becomes so common it attracts attention from predatory fish and starts looking like old hat to female guppies.

A sample of male guppies, caught from Alligator Creek, North Queensland, where they occur ferally. The size and placement of colour spots in male guppies is among the most genetically variable traits yet studied.
Rob Brooks

The selective advantages enjoyed by rare colour patterns explain why guppy colour patterns are among the most genetically variable traits yet studied. Could more subtle forms of NFD selection explain why so much genetic variation persists in most traits, even though natural selection is expected to remove genetic variation by eliminating “bad” genes. Under NFD, “good” or “bad” depends on how common the gene is.

What if, we speculated, rarity also operated in the world of fashion? In this case, what if rare patterns of facial hair enjoy an advantage purely on account of their rarity?

Experiment

To test this idea we set up a simple experiment using a suite of photographs of 36 men. Each man had been photographed when clean-shaven, with five days of growth (we call this light stubble), 10 days of growth (heavy stubble) and at least four weeks of untrimmed growth (full beard).

One subject displaying the four levels of beard: clean shaven, five-day growth, 10-day growth and full beard.
Barnaby Dixson

Subjects, recruited via our research group webpage (where we are always seeking subjects and Facebook – thanks IFLS for the traffic), each rated 36 faces – one of each man. Over the first 24 faces we manipulated the rarity of beard types. Subjects either saw all 24 men clean shaven, all 24 with full beards, or six men from each of the four levels of beardedness.

We then analysed how subjects rated the same – last – 12 pictures comprising three from each beard level. In line with our prediction, when clean-shaven faces were rare (among the early 24 pictures) they enjoyed a significant premium in attractiveness ratings (in the last 12) over when they were common. And when full beards were rare or when the four levels of beardedness were evenly distributed, full beards enjoyed significantly higher attractiveness than when full beards were common. Five- and 10-day stubble did not really vary in attractiveness across the three treatments.

What this means is that, under experimental conditions at least, patterns of facial hair enjoy greater attractiveness when rare than when they are common. Whether this scales to more nuanced judgements in the more complex and varied real world remains to be seen. But it suggests that beard styles are likely to grow less attractive as they become more popular. And that innovative new styles may enjoy a premium while they are still rare.

Fashion and facial hair

Negative frequency dependent choices might well be an important ingredient in changing facial hair fashions. The current fad for facial hair is just the latest development in a long history.

Dwight E. Robinson went to the trouble of scoring the facial grooming of all men pictured in the London Illustrated News between 1842 and 1972. In the 1890s, more than 90% of men pictured had some form of facial hair, a figure that dropped to below 20% by 1970. Sideburns occupied the news in the mid-19th century, whereas full beards reigned from 1870 to 1900, only to be replaced by moustaches.

Negative frequency dependence might play a role early in an establishing fashion.

The New York Times reckons the current beard trend emerged among local hipsters in late 2005. I’m not sure the NYT would notice anything that happened or – heaven forbid – started outside of Manhattan or Brooklyn. But suffice to say the current fashion has been almost a decade in the making.

Noveau-beard has been propelled along the way by various sportsmen, movie stars and musicians. But the fashion has now spread to the point where astute commentators reckon the tide of hipster cool has turned. When Buzzfeed breathlessly lists the “51 Hottest Hollywood Beards”, it’s time to seek higher ground to avoid the tsunami set off by the implosion of cool.

That is one way in which negative frequency dependence can work: when a fashion goes mainstream it loses the advantage of rarity. And so it begins to subside.

“Joaquin Phoenix is a Poser”. Graffiti stencil, New York City.
David Shankbone/ Flickr

Not everybody should grow a beard

Much of this discussion has concerned the attractiveness of beards. But although many hirsute men have formed the zealous conviction that their beards place them at an advantage with the ladies, evidence is far more equivocal.

Dixson’s previous research has shown that heavy stubble – a substantial growth that is well kept – is more attractive than clean shaven, light stubble or a full beard. And individual women vary in their tastes, some are pro, and others vehemently anti-whisker.

Far less ambiguously, beards tend to make those men who can grow them look more masculine. Hardly surprising, actually, given the ability to grow facial hair kicks in during puberty, marking the transition to manhood. The beard might be as much a signal to other men as it is to women, which might explain why so many warrior cultures grew resplendent beards, and why professional sports teams grow beards in playoff-time solidarity.

Female attraction to bearded men can arise due to the manly connotations of facial hair. Nicki Daniels certainly makes this point in her hilarious Open letter to bearded hipsters.

Unfortunately, you guys have turned it into a fashion statement. The beard has turned into the padded bra of masculinity. Sure it looks sexy, but whatcha got under there? There’s a whole generation running around looking like lumberjacks, and most of you can’t change a fucking tire.

If the messages signalled by growing facial hair are diminished when every man-boy over 20 is sporting a beard, that constitutes another way in which negative frequency dependent choice might work.

The reasons beards diminish in value when everyone is wearing them remain to be teased apart, but the fact that they do suggests that the hipster beard, like the handlebar moustache, the mutton chop and countless other fashions before them, will, in time, pass.


“Jimmy Niggles”, grew Australia’s highest-profile contemporary beard to raise awareness about melanoma. Now he’s looking to sell it for A$1million to support cancer research.
Tim Jones

P.S. Beard Season is coming up

You may already have encountered Jimmy Niggles (aka Scott Maggs) and friends who are raising awareness about melanoma – in honour of their mate Wes who lost his life to melanoma at age 26 – through their Beard Season campaign. Jimmy uses his resplendent beard to start conversations with strangers (and leverage considerable media interest) about the importance of having their skin checked. Jimmy is currently selling his beard for A$1 million in order to raise money for melanoma research.

Talk about a positive expression of contemporary masculinity.


The Conversation

Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

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Can monogamy undermine intelligence?

Yes

At least over 100 generations in Drosophila melanogaster vinegar flies.

“Male cognitive performance declines in the absence of sexual selection” proclaim Brian Hollis and Tadeusz Kawecki in the title of a paper out this week in Proceedings of the Royal Society of London B.

It’s the kind of experiment I love to see done – in somebody else’s lab. Set up some populations (lines) of a fast-breeding animal. Let some lines compete for mates but impose strict life-long monogamy on the other lines. Repeat. Then, a couple of years down the line, if all goes well, measure various traits you predict will be affected by the presence (competition) or absence (monogamy) of sexual selection.

Normally, monogamous lines end up more productive. When there is no advantage to males of jostling for dominance over one another or competing frantically for female attention, the fittest males are usually those that stay alive and don’t harm the females. But in lines where males have to compete with one another, females often end up collateral damage of the robust competition between males and even the chemical warfare between their ejaculates.

But this particular paper looked at male smarts.

Put a male vinegar fly into a vial with one receptive and a few non-receptive females, and he will court them all. How quickly he realises which female he should be courting can be used as a measure of his mating savvy.

No surprises that this measure of smarts declined after 100 generations of enforced monogamy. Each monogamous line male comes from a long line of male flies who never had to decide which female to court.

But it turns out that males from monogamous lines were also much slower to learn to associate a particular smell with the likelihood of their vial being shaken (a nasty thing for a fly to endure). So, it seems there’s some kind of general decline in cognitive performance in those lines where monogamy has been enforced for 100 generations.

Sexual selection for smarts

It’s a pretty neat finding from a purely genetic and evolutionary point of view. That removing the normally hectic competition among males (by enforcing monogamy) to find, court and sometimes coerce female flies leads to the whithering of cognitive performance reveals the role of sexual competition and mate choice in the evolution of cognitive capacity.

Of course the Drosophila study says very little directly about human intelligence. It’s value – apart from the discipline-specific genetic issues it addresses – is the clean experimental evidence it provides that sexual selection can favour the evolution of cognitive performance.

But this evidence cannot help but stir human curiosity. To what extent do we owe our much-celebrated human intelligence to sexual selection?

In The Mating Mind, evolutionary psychologist Geoffrey Miller made the intriguing case that we owe much of human intelligence to the never-ending competition to out-compete our rivals in love and to find, court, keep and even manipulate potential mates. In the past decade or so, support for Miller’s hypothesis has accumulated from a variety of sources.

Does this mean we’re getting dumber?

Ever since Darwin gave us a viable process – natural selection – by which evolution occurs, some thinkers have fretted about whether people are getting dumber. In 2012 I wrote about one such argument in which Stanford geneticist Gerald R. Crabtree lamented that humanity is “almost certainly” losing its superior intellectual and emotional capacities.

Such worries seem to come from a misplaced nostalgia about the purifying nature of natural selection in the past. The idea that back-in-the-day, those of below average intelligence fell victim to lions, wolves or starvation. But modern human institutions, by mollycoddling the intellectually weak, are somehow undermining our collective genetic intelligence.

It’s the kind of argument one might expect to find in a 21st Century tabloid lamenting the rise of the welfare state. But it’s not too far from Plato either.

Coming from exactly this position, Herbert Spencer mangled Darwin’s idea of natural selection into the pithy but hopelessly wrong notion of “survival of the fittest”. When Spencer co-opted natural selection to substantiate laissez-faire capitalism and oppose the “poor laws”, he diminished evolutionary thinking in a way that it has never quite shaken.

Likewise, Francis Galton drew on the work of his cousin – Charles Darwin – to argue that governments protecting the weak and infirm thwart natural selection’s role in improving humanity. In so doing he gave us several important statistical concepts, including correlation, regression to the mean. And he extended it to suggestions for action that initiated modern eugenics, another shameful perversion of evolutionary thinking.

The idea that human intelligence is on a slippery evolutionary slope lubricated by the protections societies provide to their less fortunate or well-endowed citizens has always been a dangerous one. But while Spencerian survival of the fittest doesn’t hold as much cachet as it once did, I am still often asked by well-meaning readers whether an apparent decoupling between intelligence and reproduction is leading us up the evolutionary garden path.

The questioners seem propelled by the same intuition that had people giggling at the band Harvey Danger’s 1997 observation that “only stupid people are breeding”. It’s an impulse that fuels much of the prurient interest in and sneering about shows like Maury or Jersey Shore.

Harvey Danger’s Flagpole Sitta. Relevance? 0:57.

It would be impossible to replicate the Drosophila experiment in humans. Randomly assigning individuals to life-long total monogamy for generation after generation is a fate, once you think of it, far worse than it even sounds. Hopefully the mistakes governments made with eugenics have taken half-baked social engineering programs of this nature off the table.

Modern civilisation has – thank goodness – eliminated many of the ghastly ways in which our ancestors could die. And that has dampened natural selection on survival. But sexual selection is always happening. And much of sexual selection’s power comes from the fact that humans aren’t life-long exclusive monogamists.

People compete for status and wealth with which to attract mates, they do the most outlandish things to get noticed and they engage in the most elaborate forms of persuasion to court and seduce their mates. Either to find somebody to settle down with, or to find another, or another. These are all expressions of intelligence, and while smarts don’t always win out, they usually help.

In fact, Mark Roeder, in his new book Unnatural Selection: Why the Geeks Will Inherit the Earth, argues that the anthropocene has seen intelligence eclipse strength vigour as determinants of success. If that is the case, then sexual selection may well ensure that 100 generations – say 2,500 years – from now, humans will have evolved to be much, much smarter than they are today.

Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

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Why the masculine face? Genetic evidence reveals drawbacks of hyper-masculine features

Miranda Kerr’s face typifies the properties of feminine youthfulness, including a short face, small chin, thick lips and small brow. Source: Eva Rinaldi, Wikimedia Commons
Miranda Kerr’s face typifies the properties of feminine youthfulness, including a short face, small chin, thick lips and small brow. Source: Eva Rinaldi, Wikimedia Commons

Studying sex differences seldom gets boring. While the origins of differences in behaviour and cognition remain fiercely – and quite rightly – disputed, we don’t sweat quite as much about why women and men differ in size and strength. The Darwinian process of sexual selection, in which genes that improve an individual’s reproductive success get inherited by the fruits of that reproduction, does a good job explaining sexual dimorphism (male-female differences) in these traits.

For most of our evolutionary past, bigger men fended off rivals for female attention and out-competed other men to secure status and resources that made them useful contributors to a family. These advantages offset the energetic costs and higher disease risk of building a bigger body. But what of other manly features? What use is masculine hairiness? Or those features that tend to distinguish male from female faces.

Like many other traits, from height to interest in the affairs of the sisters Kardashian, facial features differ between women and men, on average, but there is much overlap between the sexes. Using just the distances between ‘landmark’ features, the differences between masculine and feminine faces come down to complex multivariate vectors, but features like brow prominence, chin size and lip thickness play a big part.

Women and men both rate female faces bearing typically feminine features as more attractive than female faces with more masculine combinations of traits. Which might explain why Miranda Kerr’s full-lipped, round-faced, small-chinned visage seems to be everywhere these days.

So it would be reasonable to predict that lantern-jawed, Neanderthal-browed men at the far-masculine end of the facial distribution would be sought-after by women. But reality is far more varied and interesting.

Women don’t usually find masculine faces more attractive than more feminine male faces. For every Javier Bardem or Josh Brolin, there’s an Orlando Bloom or Zac Efron down the girly end of the man-tinuum. More studies report an overall preference for ‘feminine’ male faces than for ‘masculine’ ones.

Javier Bardem’s prominent cheeks, large brows and jaw give his face an exaggerated masculinity. Georges Biard, Wikimedia Commons
Javier Bardem’s prominent cheeks, large brows and jaw give his face an exaggerated masculinity. Georges Biard, Wikimedia Commons

It seems that women vary in how attractive they find masculine faces. Women at the fertile peak of their cycle favour more masculine faces, or at least less-feminine ones, than women not at the fertile peak or on the pill. Women who rate their own partners as highly masculine, or who describe their ideal partners as highly masculine, prefer more masculine faces in experiments. And women contemplating once-off sex or infidelity are keener on masculine-looking men.

The prevailing view in evolutionary psychology is that highly masculine men make great sperm donors but not necessarily awesome partners and fathers. First the downside: highly masculine men are less committed as fathers and partners, less cooperative, more sensation-seeking in outlook and more likely to seek short-term sexual encounters than less-masculine looking men. These downsides of pairing with a masculine man are thought to result from testosterone’s effects on behaviour.

While low-T, less-masculine guys might make better long-term partners, there might be benefits of a fleeting attraction, at peak fertility, to manly men if they are more likely to sire genetically well-endowed kids. It’s an idea bolstered by the findings that women living in countries with lots of disease prefer faces of more masculine-looking men. As do women primed with images of body fluids, skin lesions and other cues of disease. Developing highly masculine features takes plenty of testosterone, an immunosuppressing hormone. Which means only those with the best immune genes can afford to be taxed with high-T levels in puberty. Or so the story goes.

This is one of those ideas with prurient appeal, but patchy evidence. It’s morphing into what my UNSW colleague Angela Moles calls a ‘Zombie Idea’: compelling and considered self-evidently true by many, but not actually that well supported. Every link, from the attractiveness of masculine facial features to the immunosuppressive nature of testosterone to the claim that masculine-looking men have good immunity genes is contested. We don’t know how big the genetic benefits to children might be, much less whether they can offset the costs to a woman of mating with a highly masculine man.

New kinds of evidence

Only with new kinds of evidence can this complex question be more rigorously tested. And such new evidence has emerged, in the form of a paper in Psychological Science by Anthony J. Lee, Brendan Zietsch* and collaborators.

From an exhaustive suite of measures taken from photographs of teenaged identical and non-identical twins and their non-twin siblings, Lee dissected the extent to which variation in facial masculinity-femininity is due to genetic variation. Interestingly, around half the variation in both male and female facial masculinity could be attributed to additive genetic variation. This is the kind of variation on which the idea of “gene shopping” for genetically superior mates depends.

The extensive genetic variation in masculinity makes more plausible the idea that choosing to mate with a masculine man can result in more attractive offspring. But the genes that made a male face more masculine did not make it more attractive. Worse, these same genes made female faces more masculine and thus less attractive. Families that make manly-looking sons tend also to make masculine-looking daughters.

Overall, this paper deals a substantial blow to the idea that masculine men make good genetic sires. Of course, the genes that confer masculinity on both sons and daughters might have other positive effects, including but not limited to improved immunity. That remains to be assessed, hopefully with the same kind of quantitative genetic evidence.

So, why the manly face?

The evidence that masculine faces predict other testosterone-dependent traits typically associated with men suggests the strong action of sexual selection, but the evidence that female mate choice drives that sexual selection is far from settled. Perhaps masculine looks, like size, are more about signalling to other men. It would be better, for the average dude, not to mess with a manly looking man in a tussle or a fight in just the same way he’d avoid a tall, muscular opponent.

Women’s varied and subtle preferences for masculine looks might be a response to the upside of having a mate who is competitive and intimidating toward other men. Some collaborators and I have shown that those countries where disease is rife and women prefer more masculine men are also characterised by high income inequality – a driver of man-on-man competition and violence. Manly, competitive men might have been better providers and defenders throughout a history more violent and competitive that suburban life is today.

Much about the variable preference for manliness and for bad boys remains to be explained. Much, I fear, might be inexplicable. Like the Tumblr “Hot and Busted” of good-looking arrest mugshots. Or the FreeJahar teens who profess to love the alleged Boston Bomber. But none of it is boring.


Disclosure: I have collaborated with Lee and Zietsch on studies of attractiveness unrelated to this new paper.

Bonus: Is this what the Village People were singing about in “Macho Man”?

Macho Man, one of the Village People’s great international nerve-touchers

Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

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