Procreate by 40, boys, or you'll start shooting blanks.

Science, technology, and life.
May 26 2006 7:27 AM

The Male Biological Clock

Procreate by 40 or you'll start shooting blanks.

Human Nature will be in recess during June and July. It will return in August. (For the latest Human Nature columns on tanning, junk food, and eugenics, click here.)

Scientists have figured out how to make something invisible. By engineering "metamaterials" that bend passing light, they could cause light to wrap around an object and converge by the time it hits your eye. You would see the space as though nothing were there, and the cloaked object would cast no shadow. Official rationale: The military is funding this research to develop "super-light electronics" and "highly efficient lenses." Unofficial rationale: The military is funding this research so we can sneak up on our enemies. (For Human Nature's take on the military technology of remote-controlled killing, click here.)

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.

Men start losing their fertility at age 40. In a study of more than 1,900 couples, irrespective of the woman's age, IVF attempts involving men 40 or older failed 70 percent more often than IVF attempts involving men younger than 30. Previous theory: Older men produce fewer kids because they get less sex. New theory: Older men produce fewer kids because they shoot more blanks. Feminist takes: 1) Ladies, stop blaming yourselves for IVF failure. 2) Ask not for whom the biological clock ticks, dude. (For Human Nature's update on instant male fertility testing, click here. For abstinence and male fertility, click here. For smoking and male fertility, click here.)

Parents are pushing TV on infants. According to a study, most 0-year-olds watch TV or videos more than an hour a day, and one of every five kids under age 2 has a TV in his bedroom. The researchers thought kids were pushing their parents for TV time but discovered it was the other way around. Arguments for TV: 1) It's educational. 2) I need to shower. 3) It's safer than letting my kid run around. 4) It's an effective incentive for good behavior. 5) It turns my kid into a zombie at bedtime. 6) I still read to my kids. 7) Everyone else is doing it. Arguments against TV: 1) It turns your kid into a zombie all day. 2) It causes ADHD. 3) Kids learn from interaction, which TV can't deliver. 4) Your mom managed to shower without putting you in front of a TV, you Boomer/GenX good-for-nothing. 5) Actually, she did put you in front of a TV, which is why you're pushing the same drug on your kids. 6) You fell for that "educational TV" crap? 7) Baby Einstein will go to hell for conning parents into this. 8) The study shows most of you who put TVs in your kids' rooms did it so you could watch your own TV shows. (For Human Nature's previous update on bedroom TV and sex, click here.)

Sleep deficiency can make you fat. In a study, middle-aged women who got no more than five hours' sleep a night were one-third more likely to gain at least 33 pounds over the following 16 years than were women who slept at least seven hours a night. For women who slept six hours a night, the increase in weight-gain likelihood (compared to women who slept seven hours) was 12 percent. Since diet and exercise failed to account for the difference, the authors suspect sleep deficiency lowers your metabolic rate or reduces your movement during the day so you burn fewer calories. (For Human Nature's previous update on sleep deficiency and car accidents, click here. For sleep deficiency and kids' performance in school, click here.)

Mandatory menstruation is ending. Doctors and women are increasingly ignoring instructions to suspend hormonal contraception from pills, patches, and vaginal rings to mimic periods. New pills and implants are continuous, and drug firms are developing more options. Arguments for continuous use: 1) Periods suck. 2) They interfere with work. 3) They increase the risk of anemia and migraines. 4) We suffer a lot more of them than our foremothers did, because we start earlier and have fewer kids. 5) The pill lowers your risk of some diseases. 6) The prescribed seven-day lull in pill use dangerously raises your risk of pregnancy. 7) I'm less cranky, and my sex life is great! Arguments against it: 1) The pill raises your risk of clots, strokes, and heart attacks. 2) The last time we embraced hormone drugs too quickly (for menopausal women), we caused unanticipated health problems. 3) It's not nice to fool Mother Nature. (For Human Nature's takes on hormonal contraception, click here, here, and here.)

Pregnancy is shrinking. The average American pregnancy has shortened from 40 weeks to 39; nearly 10 percent of babies are now born at 34 to 36 weeks. Reasons: 1) Moms are older or fatter, with more complications. 2) More assisted fertility is causing more twins. 3) Technology allows earlier detection of trouble. 4) Doctors are more confident that technology can nurse preemies to health. 5) Doctors fear lawsuits if they don't advise you to deliver early. 6) Moms are choosing when to deliver. Arguments for the trend: 1) Fewer stillbirths. 2) Lower risk to moms. 3) Don't kid yourself that the baby is always safer in the womb. Arguments against it: 1) Late preemies face more long-term health and developmental problems than full-term kids. 2) We'll all have to pick up the tab. 3) Moms' schedules and doctors' fear of lawsuits are lousy reasons to pull the plug early. (For Human Nature's take on artificial wombs, click here.)

A study hints at the mechanics of prejudice in your brain. College students were asked how two hypothetical people—a young liberal and a fundamentalist conservative—might feel about various questions. The students relied more on a frontal brain region while thinking think about the liberal but relied more on a back region while thinking about the conservative. Previous research suggests the frontal region is involved in putting yourself in another person's shoes. Researchers' conclusions: 1) You discriminate against people different from you by using stereotypes rather than empathy to guess how they think. 2) So the key to fighting prejudice is to help people see others as similar. Cynics' view: We could have told you that much. Good luck with the hard part. (For a previous update on bigotry as a mental illness, click here. For Human Nature's take on Bill Bennett's prediction of the black crime rate, click here.)

Botox appears to cure health problems it wasn't designed for. In a very small pilot study, nine of 10 depressed patients "recovered from their depressive symptoms" after getting Botox injections between the eyebrows, and "even patients … who were not seeking cosmetic improvement showed a dramatic decrease in depression symptoms." In a larger study, it significantly improved bladder function (especially incontinence) in seven of every eight patients with severely overactive bladders. Old theory: Botox makes you feel better about the way you look, which relieves your depression, which makes you stop scowling. New theory: Botox makes you stop scowling, which directly relieves your depression because feedback from facial muscles regulates the brain. Alternative theory: Botox makes other people feel better about the way you look, which helps you get along better with them, which relieves your depression.

Alabama approved an alligator-hunting season for the first time ever. Arguments made for the hunt: 1) Gators are proliferating. 2) They're eating pets, invading backyards, and "terrorizing" people in south Alabama. 3) They're spreading inland. 4) They're attacking and sometimes killing humans. 5) Volunteers can't keep up with residents' pleas to remove them. 6) Putting gators on the endangered species list 20 years ago worked a little too well. Arguments made against the hunt: none.

Southern Illinois University is bracing for another round of deer attacks on humans. This year's fawning season is about to peak; during last year's peak, at least four people were hospitalized and three were injured or threatened by deer. In one case, a deer charged a woman, knocked her down, snorted, and repeatedly kicked her, bruising her and "slicing open one of her ears." Authorized explanations: 1) It's our fault for invading their habitat. 2) It's our fault for approaching them. 3) It's our fault for trying to pet their fawns. 4) The mommy deer are just protecting their young. Unauthorized explanation: There are too many deer and not enough hunters. Call Dick Cheney! (For Human Nature's previous updates on attacks by alligators, chimps, and lions, click here, here, and here.)

Latest Human Nature columns: 1) The creeping logic of embryo weeding. 2) The war on tanning3) Gay covenant marriage. 4) Polygamy and Big Love. 5) The war on fat. 6) Does God answer prayers? 7) The blurred line between contraception and abortion. 8) Gay marriage vs.  polygamy. 9) Stop giving healthy people Social Security. 10) The temptation of remote-controlled killing(Click here to return to top of page.)