Domestic Animals Have Unique Characteristics
Why So Few Species Can Be Domesticated
Jul 14, 2008 Scottie V. Westfall
Although humans have tried to tame a wide variety of animal species, most of these attempts have been failures. Only a few animal species have the temperament and biological traits to make good domestic beasts, because very few species will put up with the constraints of captivity and selective breeding. It is because of these constraints, domestic animals share certain characteristics in their behavior and biology that have allowed humans to selectively breed genetically tame populations of these animals. Most of these domestications have occurred in ancient times, for no large species has been added to the list of domestic animals since 1500 BCE. Because of the ancient roots of domestication, the animals that were successfully domesticated tend to share certain traits. These traits are relatively rare in the natural world, and because of their rarity, the number of domestic animal species is relatively small.
The Biological Criteria
Jared Diamond in Guns Germs and Steel: The Fates of Human Societies argues that domestic animals share certain traits. The first of these is that animals that can be domesticated generally have a flexible and mostly vegetarian diet. Animals that can eat grains and other plant-derived food are much less costly than animals that eat meat. Diamond points out that dogs are carnivores, but their diet is much more omnivorous than other large carnivores and can survive on a diet that includes a lot of grains, fruits, and vegetables. Animals that can be domesticated also tend to have fast growth rates, allowing humans to selectively breed these animals over several generations within the lifetime of the humans involved in the domestication. Remember, the average life expectancy of humans during the period of domestication for most of these species was much shorter than our life expectancy. A quick growth rate was necessary for domestication. It goes without saying that the animals also must be able to be bred in captivity, because it would be impossible to selectively breed animals that will not reproduce in captivity at all.
Behavioral Criteria
Diamond has temperament criteria, too. The animals have to possess a gentle disposition, meaning they come from species that do not consider humans prey or from species that develop surly dispositions as adults. They also have a very low tendency to panic, because flighty animals can never relax in captivity. All of these animals also have a social hierarchy that can accept humans as the leader of the hierarchy, which gives humans control over the animals.
Lack of Large Domestic Carnivores
If one looks at the list of criteria for domestication, one sees that very few species can be domesticated. Domestic dogs are the only large animals that do not seem to fit the criteria as clearly as others. Dogs were domesticated from the gray wolf, a somewhat omnivorous species, before the advent of large scale agriculture. How it was domesticated in the first place has been debated among scientists for years, with lots of speculation about scavenging wolf populations and hunter-gatherers keeping pet wolf pups. Smaller carnivores have been domesticated, like the cat and the ferret, but these animals were domesticated for their rat and mouse killing ability. The animals fed themselves through their hunting behavior, which was the utility for which they were domesticated. However, no other large carnivores have been fully domesticated.
The Domestication Process
Domestication is a process that is still being explored. In the former Soviet Union, a geneticist named Dmitri Belyaev began an experiment on the fur-farmed variety of the red fox, called the silver fox. He and his team selected for tameness among their fox population. After twenty generations, they wound up with foxes that wagged their tails at people, communicated with barks, possessed floppy ears and curled tails, and had two estrous cycles per year. His domestication experiment showed how quickly domestication could happen, but he had a well-designed facility for his foxes. Ancient man had none of these conveniences. It clearly shows that these criteria that Diamond discusses were very important in the domestication of animals. These criteria are why the number of domestic animals is so low.
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