Suppose you wanted to build the perfect dog from scratch. What would be the key ingredients in the recipe? Loyalty and smarts would be musts. Cuteness would be as well, perhaps with gentle eyes, and a curly, bushy tail that wags in joy in anticipation of your appearance. ... You needn’t bother trying. Lyudmila Trut and Dmitri Belyaev have already built it for you. The perfect dog. Except it’s not a dog, it’s a fox. A domesticated one. They built it quickly—mind-bogglingly fast for constructing a brand new biological creature. It took them less than 60 years, a blink of an eye compared to the time it took for wolves to become dogs. They built it in the often unbearable negative 40 degrees Fahrenheit cold of Siberia, where Lyudmila and, before her, Dmitri, have been running one of the longest, most incredible experiments on behavior and evolution ever devised. ... Except for house pets, most domesticated animals do not form close relationships with humans, and by far the most intense affection and loyalty forms between owners and dogs. What made the difference? Had that deep human-animal bond developed over a long time? Or might this affinity for people be a change that could emerge quickly, as with so many other changes Lyudmila and Belyaev had seen in the foxes already? Would living with a human come naturally to a fox that had been bred for tameness?