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.

This article was originally published on The Conversation.
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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.

This article was originally published on The Conversation.
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A complex cocktail: alcohol, sex and cute monogamous mammals

Influencing the drinking patterns of others. Apart from being in a short, overly fussy glass and sporting a slice of lemon rather than a lime, the good thing about these gins and tonics is they were made by somebody else. And so I’m not complaining. Source: cyclonebill/Flickr
Influencing the drinking patterns of others. Apart from being in a short, overly fussy glass and sporting a slice of lemon rather than a lime, the good thing about these gins and tonics is they were made by somebody else. And so I’m not complaining.
Source: cyclonebill/Flickr

How does alcohol consumption affect romantic life? Let me count the ways.

If popular advertising is to be believed, the consumption of high-end spirits almost guarantees a steady variety of glamorous amour. I was always surprised that James Bond – before Daniel Craig – opted to take his vodka martinis shaken rather than stirred. Bond was never short of anyone to stir his martinis.

From Dutch courage to a shared glass of champers to drunken would-rather-never-remember sex, alcohol’s tendency to reduce our inhibitions has changed the way drinkers meet and mate. But drinking is also a cause and a consequence of relationship breakdowns and considerable associated misery.

Which is why I’m fascinated to see how the world’s media covers a paper out today in the Proceedings of the National Academy of Science of the US (PNAS). It has an irresistible combination of clickbait-ready elements: a cute small mammal, booze and serious questions about monogamy.

The first element, the cute mammal, is the prairie vole, poster-child for wishful thinking anthropomorphising about monogamy and the power of love. Male-female pairs form long-lasting bonds, sleeping together, grooming one another and raising pups together.

The prairie vole looks even more virtuous alongside its shadier close relative, the montane vole, which tends to mate promiscuously and form no such pair bonds. Which means comparisons of the two species, from ecology to the molecular biology of receptors on the brain, can help resolve the mechanisms involved in prairie vole monogamy.

Early work on these species implicated the hormones vasopressin and oxytocin. Block their release in prairie voles, and they come over all promiscuous – just like montane voles. And it turns out the reward centres of prairie vole brains bustle with receptors for these hormones, but montane vole brains don’t. Decades of work on these closely related vole species have resolved, in considerable detail, the brain regions, receptors and molecules involved in regulating prairie voles’ much-admired mostly monogamous ways. Last June even saw the 21st century’s dark magic – epigenetics – implicated in understanding the neuroscience of how prairie voles “fall in love”.

But like so many mythologised monogamous relationships, a dark secret stalks the prairie vole love story. Because the vole has a bit of a drinking problem.

Not only do voles “self-administer” in much the same way that I do when I mix a gin and tonic, they can also “influence the drinking patterns of a social partner” in exactly the same way I do when I make one for a friend or beloved. But instead of the taste sensation of Hendricks, tonic and a quarter lime, the little fuzzies opt for a 1:10 mix of ethanol and water. They prefer it to plain water.

With an eye for a compelling study, Allison M.J. Anacker and colleagues saw an opportunity to study how self-administered alcohol consumption affects social bonding and the neural mechanisms by which prairie voles form monogamous couples. The effects of alcohol, it turns out, differed between female and male prairie voles.

Huddling up together is a reliable predictor that a couple of voles are likely to mate. Male voles that drank alcohol during a period of cohabitation were as likely to huddle up with a strange female as with a sexually receptive partner. Males who drank only water strongly preferred the partner animal over a strange female. Alcohol, it seems, disrupted the males’ tendency to behave like monogamous paragons of pair-bonded virtue.

Female voles that had been drinking alcohol, on the other hand, grew slightly more likely to huddle up to their partner and not a strange male. It seems that alcohol might enhance female pair-bonding at the same time as diminishing the male commitment to pair-bonding.

Detailed study of the voles’ behaviour as well as, eventually, their brains, revealed that alcohol directly affected the brain structures responsible for pair bonding rather than exerting indirect effects by causing drowsiness or altering levels of aggression. Alcohol, drunk during cohabitation with a potential mate, seems to affect male and female brains and behaviour differently.

Of course humans aren’t voles. Deciding how much to infer about human behaviour from a study on some other organism always presents a tricky challenge. It would be far too much to infer that drinking influences human pair-bonding in exactly the same way as it does for voles. But it would be ignorant to imagine that voles can teach us nothing of value here.

Insights from voles have already led to intriguing findings about the roles of vasopressin, oxytocin and their receptors in human commitment to their romantic partners and families. Men with a particular form of the vasopressin receptor gene, for example, exhibit a suite of traits that suggest they don’t form the same deep pair bonds that other men form: they make less committed partners, suffer from more marriage problems, are more likely to be unfaithful mates and, as a result, their relationships don’t last as long.

Alcohol inhabits a prominent yet complex place in the social and sexual lives of many adults. It can enhance bonding, ease courtship and foster closeness. And it can both moderate and cause stress, dominance/control issues and violence. The issues surrounding alcohol are so important, and so pervasive, that they should not be oversimplified or narrowly construed.

For me the most interesting thing about the vole study is the sex-specific way in which alcohol influenced pair bonding and behaviour. The study of sex differences in brain anatomy and function is an area replete with controversy and contesting ideological claims. Here is an area in which the study of sex differences can transcend simplistic ideological bickering about sexism and gender-free wishful thinking. Surely understanding the ways in which environments, genes and brains interact – over questions as socially pressing and consequential as alcohol and family function – could potentially be harnessed to great effect.

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.

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