Charles Darwin was intrigued with so many evolutionary puzzles. One thing that vexed him was why so many domesticated animals, particularly dogs and livestock, tended to have drooping ears. “Our domesticated quadrupeds are all descended, as far as is known, from species having erect ears,” Darwin pointed out in “The Variation of Animals and Plants under Domestication.” “Cats in China, horses in parts of Russia, sheep in Italy and elsewhere, the guinea-pig in Germany, goats and cattle in India, rabbits, pigs and dogs in all long-civilized countries.” Darwin noted that wild animals constantly use their ears like funnels to catch every passing sound. The only wild animal with non-erect ears, according to his research at the time, was the elephant. “The incapacity to erect the ears,” Darwin concluded, “is certainly in some manner the result of domestication.” A Russian geneticist bred silver foxes, choosing each generation based on their friendly personalities. (Photo: Newfiewild/Shutterstock) All sorts of things happen, Darwin noted, when animals become tame. It isn’t just their ears that change. Domesticated animal...