The popular belief is that people domesticated dogs and then decided to breed them smaller, working down from the larger dogs. But the latest research has shown that this may not be true. The gene for small dogs existed long before dogs were domesticated.

Researchers at the National Institutes of Health have identified a mutation in a gene related to the growth hormone that causes small body sizes in the DNA of a 54,000-year-old wolf which existed before domestication.

Today’s dogs only have 25 known genes that regulate body size, making it easier for researchers to further investigate how they work. Future studies may help breeders produce better dogs with less defects.

This study is important because it shows that the common belief that purebred dogs have more defects than mixed breed dogs is not always true. This study illustrates those defects such as size, existed pre-breed creation. Also, by identifying and understanding the gene that causes size defects such as dwarfism, which exists in humans and dogs, then there may be a future way to identify and possibly prevent these defects.