Did Neanderthal genes make us smart?

(For the latest Human Nature columns on alcohol, cybersex, and Rush Limbaugh, click here.)

Breeding with Neanderthals may have improved the human brain. Evidence: 1) Humans reached Europe, where the Neanderthals were, around 40,000 years ago. 2) Humans and Neanderthals occasionally interbred. 3) A gene that regulates brain size appeared in humans 37,000 years ago. 4) The gene is more common in Europe than in Africa, which lacked Neanderthals. Ugly old theory: We wiped out the Neanderthals because we were smarter. Sensitive new theory: We fell in love with Neanderthals and had smart babies together. Hybrid theory: We had smart babies together, and our babies wiped out the Neanderthals. (For Human Nature's previous update on sex with Neanderthals, click here. For brain evolution, click here.)

China imposed a one-dog policy in parts of Beijing. New rule: "Only one pet dog is allowed per household," and "large dogs will be banned. Anyone keeping an unlicensed dog will face prosecution." Reason: Rabies has been killing thousands of Chinese each year and killed 318 in September. Objections: 1) This is just like China's brutal one-child policy, which punishes people for having two or more kids. 2) Vaccinating dogs against rabies is more effective and less totalitarian. Defenses: 1) China has already told people to vaccinate their dogs. 2) With 100 million or so unregistered dogs running around, it's more humane to restrict people to one dog so they can care for it properly. 3) Otherwise, the government will end up slaughtering hundreds of thousands of dogs, as it did this summer. 4) Speaking of unpleasant alternatives, "Dog meat is eaten throughout the country, revered as a tonic in winter and a restorer of virility in men." (For Human Nature's take on the perversity of dog breeding, click here. For dog-eating, click here.)

Missouri passed a ballot measure to prevent restrictions on embryonic stem-cell research. Opponents' spins: 1) You baby killers spent $30 million lying to voters about the benefits of ESC research and the legality of cloning under the ballot measure. 2) All you got for your money was a 13-point slide in the polls, nearly enough to lose. Supporters' spins: 1) You right-wing whack jobs drove down our support by using priests and pastors to lie to churchgoers about cloning people and strip-mining fetuses. 2) No thanks to you, we prevented Missouri from earning a reputation as a nest of yahoos. (For Human Nature's take on strip-mining fetuses, click here. For Rush Limbaugh and Michael J. Fox on stem cells, click here. For Catholics and stem cells, click here. For political hype about stem cells, click here.)

Birth control pills are "associated with an increased risk of premenopausal breast cancer," according to an analysis of studies in the Mayo Clinic Proceedings. The World Health Organization recently classified such pills as carcinogens; the link may help to explain why U.S. breast cancer has been increasing. Caveats: 1) "The absolute risk ... is very small." 2) The increased risk gradually disappears after you stop taking the pills. 3) We're not saying you shouldn't take them; we're just saying you should be informed of the risk. 4) You should also be informed that the pills "decrease the risk of ovarian and endometrial cancer" and help fight ovarian cysts and pelvic inflammatory disease. (For Human Nature's take on birth control and abortion, click here.)

New York City will let its natives change the sex on their birth certificates without changing their bodies. Old rule: You had to get sex-reassignment surgery. New rule: You need recommendations from a doctor and a therapist, and you have to live your "adopted gender for at least two years." Arguments for the new rule: 1) Gender is more complex than genitals. 2) Your official status shouldn't contradict your chosen identity. 3) You shouldn't have to get surgery to change your identity. 4) Some people can't afford the surgery. Arguments against it: 1) It's wrong and dangerous to revise historical facts. 2) This will become a ruse for gay marriage. 3) Some guy already harassed women in a ladies' bathroom, claiming to be a lesbian. (According to the NYT, "The Metropolitan Transportation Authority also agreed last month to let people define their own gender when deciding whether to use the men's or women's bathrooms.") Arguments for going beyond the new rule: 1) Therapy, like surgery, is unnecessary and too expensive. 2) Why only two sexes? (For Human Nature's take on transsexuality and transhumanism, click here.)

A 25-year study in New Zealand suggests circumcision can reduce sexually transmitted disease "by up to one half." The study's "356 uncircumcised boys had a 2.66-fold increased risk of sexually transmitted infection compared with the 154 circumcised boys." The difference persisted even after adjustment for number of sex partners, rates of unprotected sex, and demographic factors.  Researchers' conclusion: There are "substantial benefits accruingfrom routine neonatal circumcision." Caveat: The American Academy of Pediatrics doesn't call for routine circumcision, since previous studies have been "complex and conflicting." (For Human Nature's take on circumcision, click here. For bloodsucking circumcision, click here.)

U.S. intelligence agencies have set up their own wiki. The system, known as Intellipedia, uses the same software as wikipedia.org and is open to analysts from 16 intelligence agencies, though not to the public. Rationale: We screwed up the Iraq intel because doubters were shut out, intimidated, or relegated to footnotes. This system invites and incorporates their input. Hype: "In the future you'll press a button and this will be the NIE."

China banned cosmetic leg-lengthening surgery. The surgery "involves breaking the patient's legs and stretching them on a rack." It was designed to correct birth defects and disfiguring injuries, but instead it "has become popular among young professionals desperate to raise their status in the country's height-conscious society." Government's explanation for the ban: "Poor techniques, operating conditions and a lack of nursing and recovery equipment have left many patients physically and psychologically scarred." The new rules allow it only on "medical grounds" as originally intended. (For Human Nature's previous update on leg lengthening, click here. For updates on why tall people get more education and make more money, click here and here. For American use of drugs to make short kids taller, click here.)

Evolution favors female promiscuity. In a study of mouse-like marsupials, "survival of babies with promiscuous mothers was almost three times as high as those in the monogamous group." Key reasons: 1) "The sperm of some males were far more successful than others." 2) "Babies fathered by these males were twice as likely to survive." Takeaway for women: "Polyandry improves female lifetime fitness." Takeaway for men: "Males with more competitive ejaculates sire more viable offspring." Fine print:  "Males usually died after a short and intense single mating season due to exhaustion and aggressive encounters with other males." (Did we mention that female promiscuity promotes big testicles and small brains in males? For Human Nature's case against promiscuity in humans, click here.)