According to a report in National Geographic News, geneticist Heidi Parker and colleagues at the National Human Genome Research Institute in Maryland compared 76 different dog breeds-both short and tall-looking for genetic differences that could be tied to leg length.
They found one-a mutation of a single gene, which seems to be responsible for the majority of short-legged dogs' stumpiness.
The mutation could have arisen as far back as 30,000 years ago. It's not clear how big a role humans, through breeding, had on the mutation's spread.
Of 20 ground-hugging breeds, 19 had the newfound gene-suggesting that most short-legged dogs, from corgis to basset hounds, share a common ancestor, according to Parker.
"We think of physical traits as being the product of little genetic changes built up over time, but here we could look at it as one major change that's captured and held on to," she said.
"There may just be a small number of major genetic changes that create all the different shapes and sizes of dogs," she added.
The genetic revelation doesn't apply just to dogs.
Parker said that other species, including humans, probably also carry single mutations that have big physical consequences.
In fact, humans have their own version of the gene that Parker connected to short legs in dogs: fibroblast growth factor 4 (fgf4).
Fgf4 hasn't been linked to short limbs in humans, at least not yet.
About two-thirds of cases of Hypochondroplasia, a type of human dwarfism, are instead related to a different gene: fgf3.
But "at least a third of the cases have no known genetic cause," Parker said. "Perhaps, the new dog-related fgf4 findings could give researchers a new route to look for," she added.