Flat faces on Bulldogs and Pugs are cute, but they can lead to breathing problems. New research shows that those faces are linked to a genetic mutation in dogs and their skull development.

Researchers from the Roslin Institute at the University of Edinburgh have studied DNA samples of almost 400 dogs. They believe they’ve found a genetic mutation that shapes the flat faces of breeds like Boxers, Bulldogs and Pugs. The researchers think that this finding also may give insight into birth defects in human children with regard to their head development while in the womb.

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The dogs in the study were pedigreed and mixed breed, and had body scans that gave the scientists access to 3-dimensional images of their heads. They took measurements of the dogs’ skulls and were able to compare those measurements with genetic information. They noted specific DNA variations that they correlated with different head shapes.

They found that a variation in the gene SMOC2 was linked to the length of a dog’s face. When there was a mutated development of that gene, the animals with that mutation were found to have much flatter faces than other canines. This flat face is also known as brachycephalic, and can cause significant health issues in those affected.

Dr. Jeffrey Shoenbeck, lead researcher, says that this finding is important as it gives more information on the genetic and molecular composition that goes into skull formation in dogs and humans.

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Humans can be born brachycephalic as well, and the researchers now believe that based on their connections, screening of the SMOC2 gene in humans can bring a diagnosis of brachycephaly in children.

Many dogs are specifically bred for their brachycephalic attributes, though more and more veterinarians caution about doing so because of the extensive breathing problems that result from this breeding.