The pug’s flat face and tight, corkscrew tail didn’t appear by accident; we engineered them. That “baby-faced” muzzle crushes airway space, making heat regulation and simple breathing a struggle.

Greenland sled dogs can trace their origins back nearly 10,000 years. In a new study published July 10 in the journal Science, paleogeneticists mapped the path of these culturally important canines ...