To elaborate on Grif's post, line breeding is no where near homosapien breeding. I've bred many vertebrates, Quail are my largest example of "line bred" species. They have lived long and great lives, with no genetic deformities. I've experienced polymorphism, but with temperatures correct, and humidity correct, i've hatched flawless chicks. A 98% percent success rate to be exact. With no deformities or un-healthy hatchlings.