SOURCE: BBC News (2-24-10)
A study published in the journal BioMed Central found a gene found in small dogs, IGF1, is closely related to one found in Middle Eastern wolves.
Archaeologists have found the remains of small dogs dating back 12,000 years in the region.
In Europe, older remains have been uncovered, dating from 31,000 years ago, but these are from larger dogs.
"Because all small dogs possess this variant of IGF1, it probably arose early in their history," said Dr Melissa Gray from the University of California, Los Angeles.
The team of researchers took samples from grey wolf populations around the world.
"We have a couple of individuals from North America, from Yellowstone and Alaska, several from the Middle East, Israel, Iran, India, China, Russia, Italy, Spain, Belarus and Belgium," explained Dr Gray.
The study says the similarity between the variant found in small dogs and that in the Middle Eastern grey wolf shows small size probably originated as a result of the wolf's domestication.
The scientists believe people may have preferred smaller dogs because they were easier to house in farming societies where space was at a premium.
Animals often become smaller as a result of domestication and the trend can be seen in cattle, pigs and goats.
Dr Gray believes the results could be useful for dog breeders: "Because we have this gene and that it affects body size it could possibly be used as a way to breed for small body size."
And she hopes small dog owners around the world will find the results interesting. "Maybe they can have a better understanding of the history of their pets and where they came from and how they likely dispersed out from the region."