for National Geographic News
The humble wiener dog's stubby little legs hold a clue to both human dwarfism and evolution as a whole, a new study says.
The key is in a newly identified gene that makes short-legged dogs, like the dachshund, so short, according to the research.
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.
And 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, study co-author Parker said. 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, she said.
"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," Parker said.
"There may just be a small number of major genetic changes that create all the different shapes and sizes of dogs."
The genetic revelation doesn't apply just to dogs.
Parker said other species, including humans, probably also carry single mutations that have big physical consequences.
In fact, we humans have our 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, she suggested, the new dog-related fgf4 findings could give researchers a new "route to look for."
Findings published in the July 17 issue of the journal Science.
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