A mutation may explain the size, but there's no excusing the cherry dress

A team of researchers, led by Melissa Gray and Robert Wayne from the University of California, Los Angeles, have traced the evolutionary history of the pint-sized pooch back to the Middle East. In a genetic study published in the open-access journal BMC Biology, the team surveyed a large sample of grey wolves, and discovered that the genetic mutation largely responsible for small body size had evolved long before wild dogs were ever domesticated by humanity.

Genetics are to blame for looks, as well as size.

All small dogs possess a variant of the IGF1 gene, and apparently, Middle Eastern wolves also have it. Previous work in the region has uncovered the fossilized remains of 12,000-year-old small domestic dogs, supporting the creature’s proposed origins. Older remains of much larger animals have been discovered in Belgium, Germany and Western russia, put the concentration of small animals in a very localized area. According to Gray, the smaller-sized animals were probably preferred by the individuals who lived in densely packed agricultural environments. A reduced size is a frequent side effect to domestication, as it has been demonstrated by goats, swine and cattle. Considering such an environment, where dogs are more likely going to live partially indoors or within confined parameters, it is likely that smaller pets were more popular than the larger dogs.