Selective Breeding Studies of Humans Best Friend

Artificial selection—as occurs when dogs are bred for certain qualities—can tak place only if the desired characteristics are under the influence of heredit . Selective breeding occurs by identifying the dogs that possess the desired characteristic and having them mate only with other dogs that also possess the characteristic. Dog breeders have been successful precisely because many of the qualities they wish specifi dog breeds to have are moderately to highly heritable.

Some of these heritable qualities are physical traits, characteristics that we actually see, such as size, ear length, wrinkled skin, and coat of hair . Other characteristics we might try to breed for are more behavioral and can even be considered personality traits. Everyone knows, for example, that some dogs, such as pit bulls, are, on average, more aggressive than most other dogs. Other breeds, such as the Labrador, are, on average, very sociable and agreeable. And others, such as the Chesapeake Bay

The Labrador Retriever (left) and the Chesapeake Bay Retriever (right) have been selectively bred for certain physical characteristics. Both have webbed feet, for example, which make them strong swimmers and excellent water retrievers. They have also been selectively bred for certain "personality" characteristics. The Labrador was bred to be sociable and friendly, whereas the Chesapeake Bay dog was bred to be loyal to only one owner and suspicious of strangers. Consequently, the Chesapeake Bay Retriever makes a good watch-dog in addition to its skills as a sporting dog. The Labrador, however, is the most popular family dog in America, most likely due to the unrestrained friendliness and cheerful disposition of this breed. Photos by Randy Larsen.

The Labrador Retriever (left) and the Chesapeake Bay Retriever (right) have been selectively bred for certain physical characteristics. Both have webbed feet, for example, which make them strong swimmers and excellent water retrievers. They have also been selectively bred for certain "personality" characteristics. The Labrador was bred to be sociable and friendly, whereas the Chesapeake Bay dog was bred to be loyal to only one owner and suspicious of strangers. Consequently, the Chesapeake Bay Retriever makes a good watch-dog in addition to its skills as a sporting dog. The Labrador, however, is the most popular family dog in America, most likely due to the unrestrained friendliness and cheerful disposition of this breed. Photos by Randy Larsen.

retriever, have a strong desire to please their owners by retrieving objects. All of these behavioral traits—aggressiveness, agreeableness, and the desire to please—are characteristics that have been established in these animals through selective breeding.

If the heritability for these personality traits in dog breeds is literally zero, then attempts to breed dogs selectively for such traits will be doomed to fail. On the other hand, if the heritability of these personality traits is high (e.g., >80 percent), then selective breeding will be highly successful and will occur rapidly. The fact that selective breeding has been so successful with dogs tells us that heredity must be a factor in the personality traits, such as aggressiveness, agreeableness, and desire to please, that were successfully selected.

The selective breeding studies of dogs conducted over the course of several decades by Scott and Fuller (1965) were critical in informing the scientific world tha personality characteristics, no less than physical characteristics, can be heritable in this species. The heritability of behavioral traits in dogs, however , tells us nothing about the heritability of personality traits in humans. For obvious reasons, we cannot do selective breeding experiments on people. Fortunately , however, there are other methods of behavioral genetics that can be used to study humans.

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