Small domestic dogs probably originated in the Middle East more than 12,000 years back, a new study has suggested.

Researchers in the US traced the evolutionary history of the IGF1 gene and found that the version of the gene that is a major determinant of small size probably originated as a result of the domestication of the Middle Eastern gray wolf.

For their study, the University of California team, led by Melissa Gray, surveyed a large sample of gray wolf populations.

Ms. Gray said: “The mutation for small body size post dates the domestication of dogs. However, because all small dogs possess this variant of IGF1, it probably arose early in their history.

“Our results show that the version of the IGF1 gene found in small dogs is closely related to that found in Middle Eastern wolves and is consistent with an ancient origin in this region of small domestic dogs.”

Previous archeological work in the Middle East has unearthed the remains of small domestic dogs dating to

12000 years ago. Sites in Belgium, Germany and Western Russia contain older remains (13,000-31,000 years ago), but these are of larger dogs.

These findings support the latest hypothesis that small body size evolved in the Middle East, according to the researchers.

Reduction in body size is a common feature of domestication and has been seen in other domesticated animals including cattle, pigs and goats.

“Small size could have been more desirable in more densely packed agricultural societies, in which dogs may have lived partly indoors or in confined outdoor spaces,” Ms. Gray said.

The findings have been published in the ‘BMC Biology’ journal.