The muscle exists, but doesn’t develop in quadrupeds because it doesn’t get used.
An incredibly strong biped like a wookie should have massive pecs. Gorillas don’t but that’s because they’re mostly quadapeds. Which I assume is what Lucas copied, but he changed the location without thinking how it would change anatomy.
Basically all animals have pecs.
The muscle exists, but doesn’t develop in quadrupeds because it doesn’t get used.
An incredibly strong biped like a wookie should have massive pecs. Gorillas don’t but that’s because they’re mostly quadapeds. Which I assume is what Lucas copied, but he changed the location without thinking how it would change anatomy.