We’ve Bred the Fitness Out of Our Domesticated Animals

October 26, 2015 | Sarah Tse

Photo credit: RSPCA

An Australian sheep was recently retrieved after spending six years in the wild and accumulating a life-threatening amount of wool. Centuries of artificial selection at our hands have turned domesticated animals into dependent creatures, incapable of surviving on their own.

Chris escaped from his flock at least five years ago, and he’s lucky to still be alive. He is a Merino sheep, a centuries-old breed prized by humans for its luxuriously smooth and downy fleece. But if evolution was allowed to have its way, Chris and his ilk would never have come into existence in the first place.

After several years on the lam, Chris had grown 40 kg of wool — almost doubling his body mass from 44 kg to 84 kg. H was spotted by a hiker outside Canberra, Australia on September 2, and rescued by the Royal Society for the Prevention of Cruelty to Animals. The RSPCA sent out a call for an expert, and their prayers were answered by Ian Elkins. The champion shearer managed to clear Chris of his woolly burden in two passes, although Chris had to be sedated to reduce his stress. He is now sporting a much more manageable coat, and will soon relocate to a cozy, welcoming farm, according to the RSPCA.

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So why can’t he be released back into the wild? Why did he ever grow such a debilitating amount of wool? None of the sheep that have been bred by farmers are fit to roam the bush on their own.

His tremendous coat presented a host of problems: if Chris hadn’t been found, he wouldn’t have survived the heat of the Australian summer. He had already suffered skin burns from urine trapped in the fleece, the wool on his face obstructed his vision, and skin parasites would have found the warm, dark environment to be a perfect home. Chris’s legs are also weak from the strain of lugging around his weight in fine Merino wool. If he had fallen over, his weight would have kept him from getting back up, and Chris would have either starved to death or become easy prey.

The problem is that over the thousands of years since humans have begun raising sheep, we’ve bred them to fit our purposes without regard for the impracticality of such traits. In particular, Merino sheep grow their wool indefinitely and never shed, no matter the season. Even if the sheep didn’t have to rely on farmers to shear them of their burden on a yearly basis, they have been bred to produce extremely soft, crimped wool that bears little resemblance to the more useful outer hair grown by their wild ancestors.

The white color of most sheep breeds would also make them extremely noticeable to predators. Chris has basically turned into a huge white target, and his heavy coat would have kept him from running away. Most breeds have also lost the horns that they could have once used for defense, as well as the instinct to run away from predators and humans alike.

Other domesticated animals have experienced more significant alterations in the name of human convenience. Most breeds of animals that are raised for consumption produce more of the fatty tissue that people find tasty, like the breasts and thighs in chickens, and less tough, stringy muscle. Chickens and turkeys can barely fly anymore. Nearly all domesticated animal species now exhibit “paedomorphism,” where their features have changed to look more juvenile, with larger heads and facial features and smaller jaws. This appearance came as a consequence of human selection for more docile, childlike behavior that would make them easier to tame.

Unfortunately, humans aren’t quite as good as nature is at selection. Up until a few decades ago, we have only been able to breed animals based on visible traits. Mutations with hidden, harmful effects were able to tag along with these selected traits, allowing them to flourish. The most conspicuous example lies in the extensive world of dog breeding. We’ve succeeded at fiddling around with dog genetics to create hundreds of breeds, each with highly distinct physical and behavioral characteristics. But generations of inbreeding to bring out those characteristics have also bestowed upon each of those breeds their own grim, inescapable health defects.

Any intelligent designer would take one look at the mess we’ve made of these animals’ genes, and toss the whole lot in the trash heap. If there’s one lesson we’ve learned from artificial selection, it’s that we can’t always get what we want. This applies to every attempt we make to tame nature for our own ends — every desirable trait comes with a dark flipside, and we have to carefully weigh the costs against the benefits of such alterations.

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