It is said that breathing squats and pullovers could expand ribcage. Wolff's law states that bones remodel over time under pressure. Breathing squats are suggested to expand the ribcage as the lungs exert pressure.
A large ribcage could house larger lungs, which helps to deliver oxygen to the muscles. The clavicles widen in response to growth of the ribcage.
Females, in contrast, have less muscle so they do not require large lungs support their muscles. Hence they have smaller ribcages.