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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Penis size may be driven by women (oh, and it matters)

How important is penis size?

Authors from the Australian National University, Monash and La Trobe provide the most complete answer yet: the size of a flaccid penis can significantly affect how attractive a man’s body is to women.

Writing in the Proceedings of the National Academy of Sciences (a journal commonly known by its initials as PNAS), Brian Mautz, Bob Wong, Richard Peters and Michael Jennions use a clever experimental manipulation of computer-generated imagery – CGI – to test the effects of variation in penis size relative to height and torso shape (shoulder width relative to waist width) on the attractiveness of male bodies to women.

While they found that torso shape was by far the most important determinant of attractiveness, penis size has about as much influence on attractiveness as height.

It’s the kind of science made for easy-reading 100 word news-porn in the tabloid press (“Size really does matter”). Or for wowser columnists to work up a morning’s indignation that a scientist somewhere did something interesting when everybody knows the rules:

Scientists should be finding new ways to extract coal-seam gas or cure the cancers that tend to afflict late-middle-age columnists (see the recent controversy when Fox News attacked Patricia Brennan’s research on duck penises).

If Tom Waterhouse wasn’t so busy swotting for Friday night football, he’d have already installed Mautz as hot favourite for the next igNobel Prize (for science that makes you laugh and then makes you think).

And yet for such a tabloid-ready topic, the paper itself is a study in how science should proceed in sober and restrained steps.

Evolution of penises

Genitalia tend to vary more dramatically than almost any other physical trait. And evolutionary biology has made stunning progress in resolving why.

For the most part, studies of animal penis size and shape have focused on the effectiveness of various structures in delivering sperm to where it needs to be, in removing sperm that a female had received from previous mates, in stimulating the female to use that male’s sperm, or even inflicting damage on the female so she would not mate again.

One of the more striking features of the human penis, when compared with other primates, is its length. Relative to body size, the human penis dwarfs that of bonobos, common chimpanzees, gorilla and orangutan. And our erect stance and face-to-face social interactions make the penis a highly conspicuous feature.

That conspicuousness has led anthroplogists and pop-scientists alike to speculate on the potential for penises to act as a sexual signal. Some have even suggested that a large penis may be a signal of more general health and vigour, and that the evolutionary loss of the human baculum (penis bone) may make the penis an honest signal because size and arousal can’t be faked. Continue reading Penis size may be driven by women (oh, and it matters)

Better than sext? The new Facebook app that could change the mating market

I’m intrigued. And horrified. And curious. And incredulous.

Twitter, that lolly-bag of random ideas, just led me to a story on the website of Cosmopolitan magazine about a new FaceBook app called “Bang with Friends”.

Catchy.

Think I might go back to Scrabble.

According to Cosmo:

The way it works is you sign into the website using your Facebook profile, and then you anonymously register interest in, erm, banging your contacts. You actually click a button called “down to bang” for the guys you’re digging – slightly creepy, but hey, it’s better than a wall post expressing your intentions. If the guy(s) you pick haven’t pushed the button for you too, thus aren’t interested, then your crush remains a secret. But, if you did make their cut, then you are both made aware, in fact the “down to bang” button will change to “awaiting bang”…yep, there’s no skirting around the issue here.

For those who need to know – How to Bang http://bangwithfriends.com/fuck/how

I’m sure the delectable balance of intrigue and horror will propel many a media story about this new app and let slip an avalanche of moralising. I don’t really want to moralise here myself. All the important stuff can still be boiled down to two words:

Consenting Adults.

The way people find each other for romance and for sex has been changing ever since there first were people. The pace of change accelerates steadily, as economies and social institutions and communication technologies change. And the self-appointed gatekeepers of sex have exploded in “moral” outrage at every step along the way.

I don’t think of myself as old, but the world of sex and relationships that young people today seem to inhabit is not a world I recognise. Mobile phones, and the internet have revolutionised the business of finding one another and establishing both interest and rapport. At the risk of revealing my inner creep, I certainly wish there had been more of this stuff around when I was younger.

But one of my main research interests is sex, and especially the different interests that often generate conflict. This conflict simmers even between consenting adults who use protection and like each other – both in Facebookland and in real life (which I am told I can abbreviate IRL). And any device that changes the mating market can be used to tilt the balance in favour of one party over another.

Hell, why did these “university aged men” invent Bang with Friends other than to get more roots? And why, for that matter, did Zuckerberg (and accomplices) invent Facebook?

Bang with Friends opens up a world of awkward. How do you proceed once you get the “awaiting bang” all clear? And if someone is “good to bang”, then how do all the old-fashioned niceties that surround consent get dealt with?

Most of all, what kind of deception can we expect and anticipate?

As Conversation columnist Lauren Rosewarne put it, in another context:

People go online and pretend they are somebody else all the time. People we know in real life demonstrate all kinds of delusion and absurdity on Facebook. Craggy paedophiles routinely go into chat-rooms and pretend to be adolescent skaters and both single and married folks rapidly drop kilos, years and play up the pep constantly on dating websites.

This app doesn’t simply change the market for those folks who are looking for a “bang”. It changes Facebook for everybody else too. If this app catches on with enough people, and not just under-laid 22-year-old straight men, then anybody could find themselves on “down to bang” lists. And how long will it be till those “awaiting bang” notifications get shamed, with screenshots and all?

And that’s the thing about technologies that change the sexual and reproductive landscape: porn, Viagra, AIDS, the pill, safe abortion, amyl nitrate, legalised prostitution, priestly celibacy, IVF, cloning, sexting, daytime ads for ashleymaddison.com, erectile dysfunction drugs, and sham drugs. Anything that I’m allowed to Google at work and you aren’t. Every one of these changes the balance of interests between partners and changes the game, for better or worse. I wouldn’t want to stop progress, but I’m fascinated and at times a little scared about the consequences.

For the meantime Facebook is already a notorious tool for stalking. I can only imagine the incentive to unfriend exes, colleagues and creepy distant acquaintances has suddenly tilted dramatically.

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.

The Conversation

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