What is Domestication?
People have domesticated dozens of animals, from horses to honeybees. Many of these creatures belong to the same species as their closest wild relatives and have essentially the same genetic makeup. Yet they look and act in ways that are quite distinct. How does it happen?
When people domesticate animals, they control their behavior in many ways. For example, animals that are being domesticated no longer choose their own mates. Instead, people control their breeding. Individuals with traits that humans prefer are more likely to produce offspring and pass on their genes. In the course of several generations, both the body and behavior of the animal are transformed.
Looking the Part
When animals are domesticated, their bodies change. Many species become smaller than their wild ancestors. Some, including dogs and pigs, tend to have shorter snouts, floppier ears, and curlier tails. White markings may show up on the face, chest, or legs. Studies show these physical traits may be genetically linked to the gentle behavior people tend to seek in their livestock and pets.
Most domestic animals are naturally social. Their wild ancestors lived in groups, with individuals responding to each other--some led, others followed. In domestic animals, the tendency to submit to others is especially strong. Generations of breeding have encouraged them to let people take the lead.
Evolving Among Humans
In the wild, animals that are well adapted to their environment live long and reproduce, while others die young. In this way, nature "chooses" the traits that are passed on to the next generation. Biologist Charles Darwin called this process evolution by natural selection. Domestic animals also evolve, but people do the selecting. Humans seek out qualities like tameness, and help animals with those traits survive and bear young. Darwin called this evolution by artificial selection.
Wild or Domestic?
When animals are domesticated, the change can often be seen in the bones. In dogs and pigs, for example, the muzzle becomes shorter in relation to the rest of the skull. By contrast, early domestic horse bones look very much like wild ones. So archaeologists studying horse remains must use other clues to tell whether they are domestic or wild.