Cheap sex tests carry a hidden cost


This article was first published in the Sydney Morning Herald under the erroneous headline “Choosing baby’s gender threatens to skew society’s sex ratio”. (The article isn’t about “choosing gender” but rather about tests to find out the sex of a foetus that might make it easier for parents who only want a child of a particular sex to terminate a pregnancy, thereby choosing the sex of the child). As with any article, the comments ranged from thoughtful and considered to whacky.

Because the article concerns abortion, the comments often polarise pro-life and pro-choice, and some accuse me of being anti-abortion. I should specify up-front that I am solidly pro-choice. Like Bill Clinton, I tend to think “abortion should be safe and legal. It should also be rare.”

For folks who have a hard time understanding why rich people are more likely to conceive boys and poor people girls, this version provides links to some longer studies. I treat the subject at some length in Sex, Genes & Rock ‘n’ Roll.

Anyway, enough editorialising, here’s the article …………………

It’s the first question anybody asks a parent-to-be: “Do you want a girl or a boy?” Propriety requires that we profess not to care, as long as the baby is healthy. Only parents with several sons feel safe to openly hope for a daughter, or vice versa.

Until recently, curious parents had to wait until the child was born before they could know its sex. Nowadays, parents can play spot-the-genitals at the 18-week ultrasound. One can find out earlier via amniocentesis, but doctors only prescribe this somewhat risky procedure when there are appreciable risks of genetic abnormalities.

Where genetic testing of the parents shows that a baby of one sex – but not the other – is at risk of inheriting a deadly or debilitating genetic condition like Duchenne Muscular Dystrophy, these methods are used to help decide whether to terminate a pregnancy.

So here’s the good news. An article published last week in the Journal of the American Medical Association shows that there is now a safe, non-invasive and cheap method for determining the sex of a foetus very early in pregnancy.

When a foetus is growing in the womb, tiny amounts of its DNA leak into the mother’s blood stream. From an expectant mother’s blood sample, labs can test for the presence of DNA from a Y chromosome. As mothers don’t have a Y chromosome, any sign of one means the foetus is male. The lack of such signs indicates a female.

The tests are between 95 and 99 percent reliable and work as early as seven weeks into the pregnancy. If necessary, the pregnancy can be terminated early on.

Suddenly, curious parents needn’t stay curious for long. A local company advertises a full test for $399, but at least one American website ships $25 kits almost anywhere in the world*. This puts sex-testing within reach of almost everybody.

This latest development certainly has me worried. Early and safe detection of a foetus’ sex makes it substantially easier to terminate pregnancies for no reason other than the sex of the foetus. That might sound far-fetched to Australian readers, but doctors in India and China, have, for decades, been aborting female foetuses to meet the parents’ strong desire for sons.

Twenty years ago, the Nobel-winning economist Amartya Sen pointed out  that women and girls in these countries are so neglected and abused that 100 million women were “missing”. From strangulation at birth to downright neglect, being born a girl has long been potentially deadly in those countries. 

Since sen’s article, the spread of cheap portable ultrasound made sex-specific abortion easier and more clinical, and there are now 200 million more males than females in Asia. In Jiangxi province in China, for example, about 137 boys are born for every 100 girls. In one Indian territory, 141 boys are born for every 100 girls. Unscrupulous doctors in Delhi and Shanghai must be overjoyed at the new sex-testing technologies, as thousands of families will pay handsomely to avoid having a daughter.

Evolutionary biology predicts that rich people, given a choice, will prefer sons more often than girls. In most societies, more women marry sons from wealthier families than from poorer families. So rich girls have a hard time finding suitable husbands, whereas their brothers are spoiled for choice. Likewise sons from poor families find it far more difficult to marry than their sisters do.

For this reason, humans evolved predictable biases in whether they conceive sons or daughters. Rich people naturally conceive more sons. One study showed that billionaires had six sons for every four daughters. And poor people are slightly more likely to have daughters. It is no surprise, then, that the wealthiest families in India, who can afford the services of the ‘right” doctors, are the families aborting daughters.

When sex ratios go awry then society suffers. When girls outnumber boys, teen pregnancies and single mothers become more common. As Herald blogger Sam Brett often laments, Sydney’s apparent “man drought” makes it awfully tough for single women to find Mr Right.

But the perils of having too many women wilt alongside the catastrophe wrought by too many men. Male-biased societies are plagued by violence and recklessness, as Australian residents of fly-in-fly-out mining towns well know. But at least itinerant miners earn good wages and many have families. In China, excess men are so common they have a name: “bare branches”. Unable to bear fruit, they live as poor anonymous transients without the family ties and community obligations that usually prevent antisocial behaviour.

Violent crime, gambling, drugs and the trafficking of women are rampant in the parts of India and China with the most male-biased sex ratios. And the tens of millions of excess men in Asia threaten not only peace and order within those societies but also regional and global stability.

Australia should be careful to avoid the kind of tragedy now unfolding in Asia. New sex testing methods won’t change the sex ratio, but they will make it a little easier for the few families wanting to choose the sex of their child to do so. Each such decision is itself a tragedy, but they can also add up to skew the sex ratio of a whole society. And that lasting catastrophe will unfold over a generation, and cannot be undone.


*The company won’t ship to China or India due to the prevalence of sex-selection there.

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Rob Brooks

I am an evolutionary biologist who thinks about sex for a living. Things I have thought and written about include the evolution of mate choice, the costs of being attractive, the reason animals age and the links between sex, diet, obesity and death. Follow @Brooks_Rob on Twitter.

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