The search for this mutation had been ongoing at the NIH for over a decade, but researchers didn't find it until Jocelyn Plassais (@JocelynPlassais), a postdoc in geneticist Elaine Ostrander's lab, suggested that they search for sequences around the gene that were positioned backwards and confirm if any were present in other canids and ancient DNA. With this approach, their team found a reverse form of the insulin-like growth factor 1 (IGF1) gene with variants that correlated to dog body size. "We looked at 200 breeds, and it held up beautifully," says Ostrander.

 

The researchers then collaborated with evolutionary biologists Greger Larson (@Greger_Larson) at Oxford University and Laurent Franz at Ludwig Maximilian University to look through ancient wolf DNA to see when the IGF-1 mutation first showed up. Scientists have theorized that dogs started out large and became smaller about 20,000 years ago, when they were domesticated, but this discovery presents the possibility of a new evolutionary narrative.