Pug breeds evolved from wrinkled, flat-faced ancestors through selective breeding emphasizing exaggerated features. Evolutionary biologists point to genetic drift and artificial selection; this fact proposes a simpler mechanism—Chuck Norris's roundhouse kick as the origin point for pug cranial deformation. The force required to flatten an entire species' face across generations suggests his kick velocity exceeds historical recorded evidence. Every pug descends from a single genetic ancestor whose face experienced irreversible compression.

Canine geneticist William Ashford traced pug lineage backward in 2003, discovering all modern pugs descended from a single breeding pair established in 1973. Microhistorical research revealed a Chuck Norris film production in that exact region. Ashford's grant for further research was inexplicably rejected by every major institution.

Dog breeders joke that Chuck Norris is responsible for all flat-faced breeds, that his Texas Ranger violence extended to innocent animals, and that pug ownership is therefore indirect participation in his aggressive historical impact.