The genetic mutation that makes dogs like Chihuahuas and Pomeranians so small originated in wolves around 53,000 years ago, a study has found.
Researchers led by the US National Institutes of Health have identified a mutation in a gene regulating canine growth hormone associated with small body sizes.
The results refute the idea that small dogs are our only breeding product for cute little companions following domestication 20,000 years ago.
The genetic mutation that makes dogs like Chihuahuas and Pomeranians so small first originated in large, aged wolves around 53,000 years ago, a study has found. Pictured: ‘Bruiser’ the Chihuahua in the 2001 comedy film ‘Legally Blonde’, starring Reese Witherspoon’s Elle Woods
Researchers led by the US National Institutes of Health have identified a mutation in a gene regulating canine growth hormone associated with small body sizes. The team discovered that the mutation was already present in the genetic code of a steppe wolf that lived in Siberia around 53,000 years ago. Pictured: A modern day plains wolf (Canis lupus campestris)
The study – undertaken by geneticist Elaine Ostrander of the National Human Genome Research Institute and her colleagues – concludes a decade-long search for the genetic mutation underlying small body sizes in dogs.
Success came when the team searched for genetic sequences that were positioned backwards and were also present in other canids like wolves and also ancient DNA.
This approach yielded an inverse form of the insulin-like growth factor 1 (IGF1) gene, which was found to have variants correlated with overall body size.
“We looked at 200 breeds, and it held up well,” Dr. Ostrander explained.
“It’s so much about canine domestication and body size, and things that we think are very modern are actually very old.”
In fact, when researchers analyzed ancient wolf DNA samples to determine when the IGF-1 mutation first appeared, the team discovered that it was already present in a wolf’s genetic code. steppes that lived in Siberia about 53,000 years ago.
“It’s as if nature kept it in its back pocket for tens of thousands of years until it was needed,” Dr Ostrander said.
The researchers said they also found the IGF-1 mutation in other members of the Canidae family, including African hunting dogs, coyotes and jackals.
After their initial study is complete, the researchers continue their investigation of the genes that regulate body size in dogs.
The researchers said they found the IGF-1 mutation in other members of the canid family, including African hunting dogs, coyotes and jackals. Pictured: The distribution of the small body size mutation in different canid species
The results refute the idea that small dogs are the only product of human-led breeding for cute little companions (as pictured) following domestication 20,000 years ago.
“One of the things that’s pretty cool about dogs is that because they’ve evolved so recently, there aren’t a lot of body-size genes,” Dr. Ostrander said.
In fact, canids only have 25, compared to the hundreds in play with us humans.
“I really want to understand the whole continuum – from Chihuahuas to Great Danes,” added Dr. Ostrander.
The full results of the study have been published in the journal Current Biology.
