Picking items for "Human Nature" is always a bit embarrassing. Should we go with the latest deep challenge to life as we know it, or the sick wire story we can't stop gawking at? The baby whose smiling, blinking second head had to be severed? The woman who gave birth to her own grandchild? The museum exhibit on gay animals? The driver who used her fetus to qualify for a carpool lane? Fish that grow meatier when you change their sex?Pro athletes who freeze their babies' stem cells to cure their own injuries? Parents who substitute bedroom TV for intercourse?
Memorable stories all, but none of them made the year's top 10. Here are the winners. (For related news and columns, you can click through to each item's original page.)
1. Scientists have grown and implanted the first custom-made human organs. They made bladders and put them in patients who donated the source tissue. Recipe: Take a tiny tissue sample from each patient, grow it in a dish, wrap it around a scaffold to shape it, grow it for seven weeks in an incubator, then put it in the patient, where the new bladder keeps growing. The bladders have been functioning in seven patients for about four years. Next, scientists plan to grow kidneys, livers, and hearts. Interpretations: 1) Tissue engineering has arrived. 2) We did it without embryonic stem cells. 3) Death, RIP.
2. In 10 years, self-reported oral sex has more than doubled among people aged 12 to 25, according to a comparison of 1994 and 2004 data in Baltimore clinics that manage sexually transmitted diseases. In a sample of more than 6,000 young people, the percentage of males reporting oral sex in the preceding 90 days rose from 16 to 32; the percentage of females reporting oral sex rose from 14 to 38. Meanwhile, the percentage of females reporting anal sex rose from 3 to 5.5. Interpretations: 1) More teens and young adults are having oral sex because they think it's safer than vaginal sex. 2) That's true of some infections but not others. 3) This is foiling urine tests, which are supposed to diagnose STDs but don't catch oral or rectal infections. 4) We'll have to warn kids more explicitly about the risks of various activities.
3. Several U.S. fertility clinics admit they've helped couples deliberately select defective embryos. According to a new survey report, "Some prospective parents have sought [preimplantation genetic diagnosis] to select an embryo for the presence of a particular disease or disability, such as deafness, in order that the child would share that characteristic with the parents. Three percent of IVF-PGD clinics report having provided PGD to couples who seek to use PGD in this manner." Since 1) the United States has more than 400 fertility clinics, 2) more than two-thirds that answered the survey offer PGD, and 3) some clinics that have done it may not have admitted it, the best guess is that at least eight U.S. clinics have done it. Old fear: designer babies. New fear: deformer babies.
4. Lesbian brains differ from straight women's brains. Last year, a study showed that gay men, like straight women and unlike straight men, processed a male pheromone in a sex-related part of the brain (the hypothalamus) but processed a female pheromone in a scent-related part of the brain. Now the authors of that study report differences among women: 1) Lesbians, like straight men, prefer the female pheromone and find it less irritating than the male pheromone. 2) Straight women find the female pheromone more irritating. 3) Straight men and women process same-sex pheromones in the scent area but process opposite-sex pheromones in the hypothalamus. 4) Lesbians process pheromones of both sexes in the scent area. Interpretations: 1) Sexual orientation is biologically based, not a choice. 2) Sexual orientation is more biologically based in men than in women.