Popular belief has been that small dogs, such as Pomeranians and Chihuahuas, exist because once dogs were domesticated, humans wanted small, cute companions. But in the journal Current Biology on January 27, researchers at the National Institutes of Health (NIH) identify a genetic mutation in a growth hormone-regulating gene that corresponds to small body size in dogs that was present in wolves over 50,000 years ago, long before domestication.
Click here for original story, Gene mutation that makes dogs small existed in ancient wolves
Source: Phys.org