The evolutionary secret of how the dachshund got its short legs has been uncovered by scientists with the discovery of a gene that explains the diminutive stature of at least 19 breeds.

Dachshunds, corgis, basset hounds and Pekingese are among the common breeds that owe their short legs to the mutation of a single gene that occurred several thousand years ago.

The discovery offers insight into the way genetic mutations drive evolution and may have implications for understanding dwarfism in humans.

In the study, a team from the American National Human Genome Research Institute, in Bethesda, Maryland, examined DNA samples from 835 dogs from 76 breeds, including 95 animals with short legs.

The scientists found that dogs from all the short-legged breeds had an extra copy of a gene that produces a growth protein called FGF4, which is known to be implicated in dwarfism in humans. The extra gene is a mutant of a type known as a retrogene, which lacks parts of the normal DNA code.

The extra retrogene leads to an overproduction of the FGF4 protein, which in turn appears to alter the times at which bones grow in embryonic development. This, the scientists believe, causes the legs of small dogs to remain short and out of proportion to their bodies. Details of the research is published in the journal Science.

As the same gene is shared between all the short-legged breeds of dog studied, the mutation is likely to have emerged early in the evolution of dogs. Fossil evidence suggests that dogs were first domesticated from wolves at least 14,000 years ago, and genetic evidence suggests the evolutionary split may have happened earlier than that.

Eric Green, scientific director of the National Human Genome Research Institute, said that the research shows how genetic information can help understand the course of evolution.

“Every species, including canine and human, carries an amazing record of evolution scripted in its genome that can teach us about the mechanisms at work in biology, as well as about human health and disease,” he said. “This work provides surprising evidence of a new way in which genome evolution may serve to generate diversity within a species.”

The research is particularly interesting because of the role it ascribes to a retrogene — a particular kind of genetic mutation that may have played a more important part in evolution than had been assumed.

When genes are active, they are copied into a signalling chemical called messenger RNA (mRNA), which is then translated into a protein in cells. When mRNA encounters a type of virus called a retrovirus, however, it can be copied back into DNA, producing a “retrogene” that can be written back into the genome.

Heidi Parker, a leader of the research, said: “Our findings suggest that retrogenes may play a larger role in evolution than has been previously thought, especially as a source of diversity within species.

“We were surprised to find that just one retrogene inserted at one point during the evolution of a species could yield such a dramatic physical trait that has been conserved over time.”

The research could also be significant for studies of human health. People with a growth disorder called hypochondroplasia have symptoms that mimic the processes involved in the evolution of small dogs, with limbs that are abnormally short.

While about two thirds of cases of this disease are already known to be caused by a different genetic mutation, the new research suggests that FGF4 and similar genes are worth studying as potential causes of the remaining cases.

Elaine Ostrander, the senior author of the study, said: “This study points to a new gene that should be investigated for its possible role in human hypochondroplasia. Our findings may prove valuable to scientists studying other aspects of human growth and development. The work also underscores the value of canine studies for uncovering new biological mechanisms that are likely relevant to human disease.”

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