A new genetic study suggests that the reason behind the tiny anatomical structures of canines like Chihuahuas and Pomeranians can be traced back to the ancient wolves. The authors said that a possible link between the genes of tiny dog breeds originated from wild wolf ancestors that have existed 53,000 years ago.
Canine Growth in Mutation and Domestication
Chihuahua dog owners release their pets to compete in the "Run of the Chihuahuas" annual race in Washington on May 3, 2014. The annual Chihuahua race marks the Mexican holiday Cinco de Mayo celebrated on May 5.
The latest research in canine origins was led by experts from the United States National Institutes of Health (NIH). The team investigated how certain modern-day dog breeds began to have small bodies through the analysis of mutation and hormone-regulating genes that are correlated to canine growth.
According to their findings, the small dogs are a product of an extensive breeding activity long before it was made normal today. Based on the timeline that the authors examined, the tiny canine first emerged during the wake of domestication 15,000 years ago.
The study was presented by National Human Genome Research Institute expert Elaine Ostrander, along with her colleagues. The paper is an attempt to conclude the search for the genetic mutation that explains the strange shrinkage in canine breeds.
The results emerged when the scientists sequenced the genomes from selected dog breeds. The data was then compared with the species' Canidae cousins such as wolves and other DNAs preserved since the ancient years.
Through the examination, a reverse form of a gene called insulin-like growth factor 1 or IGF-1 was extracted. Among the pool, the specified gene was found to have multiple variants that are associated with canine's body size.
Ostrander said in a report by DailyMail that the genomes were identified in each of the 200 breeds they observed in the investigation. The author explained that their comprehensive approach filled the gap between the unknown factors of domestication and the body sizes of dogs. Moreover, Ostrander said that the aspects we thought to be modern are instead rooted in ancient mutations.
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Gene Mutation in Ancient Wolves Found in Modern-Day Dogs
The IGF-1 gene mutation found in wolf subjects started approximately 53,000 years ago. This is because the same genetic code was present in steppe wolves, canids that are commonly found in ancient Siberia.
Ostrander explained that nature somehow kept the secret around the domestication and mutation of dogs for thousands of years before they emerged. Additional members of the canid family that were discovered with the same IGF-1 gene mutation are coyotes, jackals, and African hunting dogs. With the information at hand, the authors expect future studies that would elaborate on how other genes regulated the growth of canine's anatomical size.
Due to the recent evolution of dogs, the authors said that there might not be a lot of gene pools that could reflect the body size in dogs. In humans, there are hundreds of genes associated with growth, whereas in canines, there are only 25 genes known. Ostrander said that they are interested in identifying the whole continuum of these genes from Chihuahuas to Great Danes.
The study was published in the journal Current Biology, titled "Natural and human-driven selection of a single noncoding body size variant in ancient and modern Canids."
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