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US states defending same-sex marriage bans say the ability to procreate naturally dictates wedding rights. This is irrational, says William Saletan

During the US Supreme Court鈥檚 oral arguments in Obergefell vs Hodges, a case challenging state gay marriage bans, Justice Ruth Bader Ginsburg raised a good question. What should states that ban same-sex marriage do, she asked, when a 70-year-old straight couple asks for a marriage licence? 鈥淵ou don鈥檛 have to ask them any questions,鈥� she , to 鈥渒now they鈥檙e not going to have any children.鈥� If marriage is for procreation 鈥� and gay couples are excluded for that reason 鈥� why aren鈥檛 old couples excluded, too?

The man to whom Ginsburg posed the question 鈥� an attorney representing four states that forbid gay marriage 鈥� had no good answer.

And his inability to explain the discrepancy cuts to the heart of the issue, because the states whose laws have been challenged in Obergefell 鈥� Ohio, Kentucky, Michigan and Tennessee 鈥� have staked their case on reproductive biology.

Last autumn, in its ruling on Obergefell, the Sixth Circuit Court of Appeals bought the biology argument. Marriage, the court , is 鈥渁n incentive for two people who procreate together to stay together for purposes of rearing offspring鈥�. In excluding same-sex couples from this institution, the court concluded, states had simply accepted 鈥渢he biological reality that couples of the same sex do not have children in the same way as couples of opposite sexes.鈥� That explanation, still relevant today, suffices to allow the states to retain authority over an issue they have regulated from the beginning.鈥�

Reject this argument

Organisations that oppose homosexual behaviour have echoed this argument in briefs to the Supreme Court. 鈥淎s a matter of simple biology, only sexual relationships between men and women can lead to the birth of children by natural means,鈥� says the .

Many of my friends reject this argument as irrational. . The distinction is solid. It really does exclude all same-sex couples. However, to apply it honestly, you鈥檇 also have to exclude . As the Human Rights Campaign in its brief to the court:

鈥淸T]here are at least three different kinds of couples who might qualify for marriage: (1) fertile straight couples, (2) infertile straight couples, and (3) infertile gay couples. Assuming for the sake of argument that the state鈥檚 only interest in marriage is to channel 鈥榬esponsible procreation鈥� (which is clearly not the case in any event), it might make sense to draw a line between the first and second groups. But, once the second group is allowed to marry, what sense does it make to draw the line between the second and third groups, who are identically situated for these purposes? After all, it is not as if the second group can 鈥榬esponsibly procreate鈥� any better than the third group.鈥�

This is a serious problem for opponents of gay marriage. They鈥檝e tried to answer it by pleading that infertile straight couples are hard to identify. To find out which couples are infertile, they argue, you鈥檇 have to invade everyone鈥檚 privacy. The bishops鈥� brief, quoting a , says states would have to 鈥済ive sterility tests to all applicants, refusing licences to those found sterile or unwilling to raise a family. Such tests and inquiries would themselves raise serious constitutional questions.鈥� The Family Research Council offers the : 鈥淪uch an inquiry would be constitutionally barred and impossible to administer.鈥�

Old folks

That鈥檚 a decent answer. But it doesn鈥檛 apply to the biggest category of infertile people: old folks. A separate brief, filed by a collection of organisations representing senior citizens, . According to , 18 per cent of men and 15 per cent of women who got married in the US in 2009 鈥� more than 700,000 people 鈥� were at least 45 years old. More than 250,000 were at least 55 years old. More than 80,000 were at least 65 years old. From 2009 to 2013, the 45-and-over segment of the just-married population increased to 20 per cent of men and 16 per cent of women. That鈥檚 more than 750,000 people, 鈥渃ouples in their eighties and nineties鈥�.

Based on these figures, the brief computes that, from a procreative standpoint, banning gay marriage but not elderly marriage isn鈥檛 just illogical. On balance, it鈥檚 counterproductive:

鈥淎pproximately 15 per cent of the marriages entered into each year involve an older couple who are almost certainly incapable of procreation. In contrast, if all legal restrictions are removed, same-sex couples are likely to account for two to four per cent of all marriages. A classification that allows a substantial number of older couples to marry despite being incapable of procreation, while preventing a small minority of older couples from marrying because they are incapable of procreation, clearly does not bear a rational relationship to the goal of restricting marriage to couples capable of procreation.鈥�

That鈥檚 a powerful indictment. And the brief goes further. It notes that 鈥渁 number of states allow otherwise unlawful marriages only if the celebrants are too old (or otherwise unable) to procreate鈥�. Arizona allows first cousins to marry one another only 鈥渋f both are at least 65 or older, or one is over 65 and the judge receives 鈥榩roof鈥� that one of the cousins is unable to reproduce'鈥�. Illinois requires first cousins to be at least 50 years old or to prove that one of them is 鈥渋rreversibly sterile鈥�. Wisconsin requires the female cousin to be 55 or older. Indiana and Utah have similar statutes.

Disappearing fertility

Why do states allow cousins to marry at age 50 or 55? Because that鈥檚 when a woman no longer has a serious chance at conception. The average age of menopause is 51, and women generally stop bearing children . By age 45, 87 per cent of women are infertile. The median age at onset of sterility is 44.7 years, with a and a . Beyond that, the outliers are in the . The oldest age at which a woman is known to have conceived a successful pregnancy without hormone treatment or donor eggs is .

At age 60 or above, there鈥檚 no record of any woman conceiving a successful pregnancy naturally. A few have used . But once you cross that line, you鈥檙e doing the same thing lesbian couples can do: using somebody else鈥檚 gametes. Opponents of gay marriage don鈥檛 accept that kind of procreation as a basis for marriage. As the bishops put it: 鈥淥nly sexual relationships between men and women can lead to the birth of children by natural means.鈥�

So age 60 clearly demarcates the point beyond which sexual relationships aren鈥檛 procreative. The state doesn鈥檛 have to ask you any questions or administer any tests. It already knows your age, because you wrote it down when you applied for the marriage licence. Read the at issue in Obergefell. Right below the section that , there鈥檚 a section requiring the parties to .

If Ohio and other states want to limit marriage based on procreation, they鈥檒l have to treat age the same way they treat sex. And Ginsburg鈥檚 hypothetical cut off 鈥� age 70 鈥� is way too lax. Any marriage application on which a woman reports her age as 60 or older would have to be rejected. The Sixth Circuit鈥檚 ruling in Obergefell implies that the line should be drawn even earlier, at 50. The judges noted that a prior Supreme Court case holds that a state may require law enforcement officers to retire without exception at age 50, in order to assure the physical fitness of its police force. If a rough correlation between age and strength suffices to uphold exception-free retirement ages (even though some 50-year-olds swim/bike/run triathlons), why doesn鈥檛 a correlation between male-female intercourse and procreation suffice to uphold traditional marriage laws (even though some straight couples don鈥檛 have kids and many gay couples do)?

Fine. We鈥檒l accept the correlation between male-female intercourse and procreation, if you鈥檒l accept the correlation between age 50 and procreation. Amend your laws to prohibit the marriage of any woman beyond that point. Or extend marriage rights to , whether gay or old.

This article first appeared on

Will Saletan writes about politics, science, technology, and other stuff for Slate. He鈥檚 the author of .