Do men have biological clocks?

Will men someday pause and see age as part of their biological equation?

Read between the lines of a recent study out of Australia and you can see hints of a coming shift in the gender conversation. Researchers at the University of Queensland found that children born to older fathers have, on average, lower scores on tests of intelligence than those born to younger dads. Data they analyzed from more than 33,000 American children showed that the older the man when a child is conceived, the lower a child’s score is likely to be on tests of concentration, memory, reasoning and reading skills, at least through age 7.

It was a small difference — just a few I.Q. points separated a child born to a 20-year-old and a child born to a 50-year-old. But it adds weight to a new consensus-in-the-making: There is no fountain of youth for sperm, no ‘‘get out of aging free’’ card. The little swimmers, scientists are finding, one study at a time, get older and less dependable along with every other cell in the male body.

And men don’t have to be all that old to be ‘‘too old.’’ French researchers reported last year that the chance of a couple’s conceiving begins to fall when the man is older than 35 and falls sharply if he is older than 40. British and Swedish researchers, in turn, have calculated that the risk of schizophrenia begins to rise for those whose fathers were over 30 when their babies were born. And another Swedish study has found that the risk of bipolar disorder in children begins to increase when fathers are older than 29 and is highest if they are older than 55. British and American researchers found that babies born to men over the age of 40 have significantly greater risk of autism than do those born to men under 30. (The age of the mother, in most of these studies, showed little or no correlation.)

Lay this latest I.Q. news atop the pile, and you find yourself reaching the same conclusion as Dr. Dolores Malaspina, a professor of psychiatry at New York University Medical Center, who has done some of the schizophrenia research: ‘‘It turns out the optimal age for being a mother is the same as the optimal age for being a father.’’

For decades men have been diligently discovering their feminine side, and couples have been announcing ‘‘we’re pregnant’’; yet the hows and whens of having a baby are still juggled primarily by women. We are the ones who hold the time lines and calendars in our heads, who have to surrender space in our bodies and clear time in our lives. Too soon could derail a career. Too late could risk infertility. Becoming a mother means compromising with biology — ‘‘settling’’ for a mate or for single-parenthood or for an ill-timed career interruption — in order to beat that clock.

The clock determines not only the odds of having a baby but also the odds of having a healthy baby. It doesn’t help that after age 35, a first-time mom finds ‘‘elderly primigravida’’ scrawled on her chart in the OB’s office. With each year comes greater risks of Down syndrome and low birth weight and prematurity. The message to women: You are the direct cause of your baby’s health; the message to men: You, too, could be Tony Randall. Women: You’d better hurry up. Men: You have all the time in the world.

The push and pull between timetables and dreams, between our bodies and our babies, is at the core of many women’s worldview, which also means it is at the core of relationships between the sexes. This tension feeds the stereotype of woman as eager to settle down and men as reluctant, and it’s the crux of why we see women as ‘‘old’’ and men as ‘‘distinguished.’’

If those underlying assumptions were to change, would all that follows from them change as well? A world in which each man heard his clock tick even a fraction as urgently as each woman could be a very different world indeed. All those silver-haired sex symbols, and balding sugar daddies, and average-Joe divorced guys who are on their second families because they can be while their exes are raising their first set of kids — what if all of them became, in women’s eyes, too darned old?

What if 30-year-old women started looking at 50-year-old men as damaged goods, what with their washed-up sperm, meaning those 50-year-olds might actually have to date (gasp!) women their own age? What if men, as the years passed, began to look with new eyes at Ms. Almost Right? Would men of all ages come to understand — firsthand, not just from the sidelines — the fear that the very passage of time will put your not-yet-conceived baby at risk?

It could happen. True, the results of these studies are incremental and preliminary — a few I.Q. points here, a few hundred schizophrenia cases there. Yet for better or worse, we humans have proved that we’ll upend our lives over a few bits of cautionary data. This seems particularly true when it comes to parenting, where our responses are often visceral, not intellectual. Suggest that something might keep a child safer, or ensure his happy future, or get her into college, and today’s parents will bite.

In that context, choosing a father for your child according to his ‘‘sell-by date’’ would be perversely consistent — seen by some women as long-overdue comeuppance (hear the chortling yet at girls’ night out?) and by others (old habits die hard) as yet another thing they have to worry about when getting pregnant.

It will not change everything; it might not even change most things. But it would be a satisfying start if men had to pause and see age as part of their biological equation, too.

“Your Old Man” by Lisa Belkin originally appeared in The New York Times Magazine. Belkin is the author of the Motherlode blog.