Maybe you’ve never thought about it, but you’ll notice the trend once you look around: many domesticated dogs have lovable, droopy, floppy ears. In fact, you may subconsciously associate gentle and slow dogs with floppy ears—who’s afraid of a Basset Hound, after all?—and guard dogs with alert, upright ears (like a German Shepherd). Why is it that some dogs have floppy ears while others are naturally upright?
It turns out, Charles Darwin asked this question in 1868, and NPR’s science show, Skunk Bear, delved into how modern science is still pondering it. Darwin’s second book, a follow-up to On the Origin of Species, spent a significant portion of its 897 pages asking why “the incapacity to erect the ears” seemed to be “in some manner the result of domestication.” In his study of animal species, he began to see the floppy-eared trend in more than just dogs; cats, horses, sheep, guinea-pigs, goats, and pigs all exhibited similar ear-differences between domesticated and wild. Domesticated animals not only showed signs of floppy ears, but they also had lighter skin and hair coloration and shorter snouts. Together, these differences are known as “domestication syndrome.” Darwin could observe the pattern happening again and again across species. But why?
The Fascinating Results of Domestication
Darwin couldn’t crack the code and answer the question why. Even a century later, his question remained unanswered when Russian geneticist Dmitry Belyayev domesticated silver foxes and saw floppy ears within a few dozen generations. He still couldn’t determine the cause of this physical change as the foxes became calmer and less likely to bite.
In recent studies, scientists have begun to discover clues that could answer Darwin and Belyayev’s dilemma. Some scientists have hypothesized that the physical results of domestication are due to a specific group of cells called neural crest cells. Neural crest cells end up in the kidneys, becoming cells that secrete adrenaline, the fight-or-flight hormone, and neurotransmitter. As you may expect, domesticated animals have less adrenaline in their systems than wild ones, and create fewer neural crest cells early in their embryonic development.
Neural crest cells aren’t just responsible for kidney cell generation, though; some of them end up in the ears, creating cartilage. Others go to cells that control skin and hair coloration, and (you guessed it) some become part of the face. It seems domesticated animals end up with fewer neural crest cells, resulting in less adrenaline and the physical appearances of domestication syndrome.
It’s true that the work Darwin began in the 1800s isn’t over yet, though; scientists still can’t explain why some domesticated animals still have upright ears, for instance. But for now, it’s interesting to see how our furry friends are different from their wild ancestors and cousins, and it’s great to know scientists are just as interested in our pets as we are.
