Peter Weisz, Puzzle Tov!: Short book of Jewish-themed brainteasers, some of them based on pretty old jokes and some requiring mathematical cleverness. I enjoyed it and was stumped by more than a few, but had the appropriate head-slapping reaction when I read the answers. For a puzzle-loving kid (or even adult) in your life.

Alan Dugatkin & Lyudmila Trut, How to Tame a Fox (and Build a Dog): Visionary Scientists and a Siberian Tale of Jump-Started Evolution: Short but fun book about the Soviet/Russian project to breed tame foxes. Wolves and foxes are related enough to make the attempt plausible, but zebras and horses are also closely related enough to breed, and zebras haven’t been successfully domesticated despite numerous attempts, nor have deer except reindeer (even though they live near humans and aren’t usually aggressive towards us, not to mention being important food animals, all of which suggests domestication would be favored if it were feasible). The Soviets picked the least reactive and aggressive foxes and bred them; calmer foxes appeared within three breeding seasons. And slightly greater tameness also shortened their breeding cycle and raised fertility a bit higher, bolstering the theory that in-bred tameness had complex effects on the whole animal. (Unfortunately, these shorter mating cycles didn’t allow multiple fox generations within the same year—although the scientists had sold the project to the Soviet government on the promise of increasing fur production, the shorter cycles meant that the mothers didn’t produce enough milk for their pups, whom they ignored. The scientists hypothesized that a longer transition might have let milk production catch up with increased fertility, as with dogs and cats and pigs and cows.)

Later generations began to exhibit tail-wagging, whining, licking hands, and rolling over for belly rubs—still later, some of the tame foxes’ tails curled, again like dogs. Tamer foxes retained juvenile behaviors longer than wild foxes—wild fox pups are “curious, playful, and relatively carefree when they are very young,” but that changes at around 45 days, when they become more cautious and anxious. After only a decade of breeding, tamer pups stayed curious and playful twice as long.

Tame foxes began gazing into humans’ eyes, which for wild animals is a challenge that can start an attack. Humans themselves, though they weren’t supposed to interact differently with the foxes, couldn’t resist talking to them, petting them, and loving them. When dogs and owners gaze at one another, both see increased oxytocin, leading to increased interactions/petting, “a chemical lovefest.” Adult foxes began to engage in object play—extended play with objects that are known—which wild animals don’t do. (Birds, chimps, and even ants play (with mock fights), but play is usually skill practice.) The tamest fox one year lived with the main researcher for a while, like a dog, and when she returned to her group, she began seeking out caretakers when other foxes were being aggressive toward her. Tame foxes began to demonstrate loyalty to particular caretakers (unlike simply being calm around humans) and jealousy of other foxes who might take their favorites’ attention. They began to bark like guard dogs when strangers appeared. They learned social intelligence: tame fox pups were as smart as dog pups in interpreting human behavior, and smarter than wild fox pups. So selection acting on tameness brought social intelligence along with it, suggesting that there was no need for humans to have bred dogs to be smarter: it could just happen.

The Soviets also tested their work by creating a line of incredibly aggressive foxes using the same selection procedures. Workers were terrified of the new line. When aggressive fox pups were swapped with tame fox pups and raised by mothers from the other line, the pups behaved like their genetic mothers. Genes clearly played vital roles, though tame foxes’ bonds with individual people also showed the role of learned behaviors. The genetic changes worked by changing production of hormones and neurochemicals, like oxytocin. These chemical pathways might help explain why the changes could happen so fast. Tame foxes had higher levels of serotonin than their wild cousins, as dogs have more than wolves.

The evidence supports a theory of destabilizing selection—genes may be similar, but the activity of those genes is very different as between wolves and dogs, chimps and humans. The dramatic changes of domestication seemed to come not primarily from new genetic mutations that were then favored by selection, though that played a role, but from changes in the expression of existing genes that led to very different results. For example, tame foxes started being born with white stars on their foreheads, which happened because the embryonic cells responsible for coloring hair had been delayed in migrating to their places by two days, causing an error in the production of hair color. The expression of the relevant gene was affected by the other changes caused by selecting for tameness. We may even have selected ourselves for tameness using similar mechanisms—we have lower levels of stress hormones in groups than our chimp cousins, we can breed all year round, and our kids stay juvenile longer, like those of other domestic species. And the bonobo may be in the process of doing the same thing, though I’m not sure they’ll have a planet to inherit when their brains get as big as ours.

Speaking of which, the collapse of the Russian economy nearly led to the fox project’s demise. Many foxes starved or nearly starved; others were selected for sale for fur to keep the project alive, a process that also deeply traumatized their caretakers. In 1999, however, a popular science article about the project came out in the US, and they received enough donations to stay afloat, because humans are sentimental. Maybe someday you’ll be able to get your own tame fox pup.

Duncan Green, How Change Happens: Green works in international anti-poverty programs, and argues for a systems approach in which one iteratively works with groups at different levels of the system, leveraging elite points of entry while taking direction from people on the ground. I thought the concept of “positive deviance” was useful—find people in the group you’re trying to help who’ve overcome the problem you’re trying to solve, and see if you can help other people do the same thing, using the positive deviants as the model.