The entire basis for my sleep-breathing paradigm is that all modern humans have constricted facial structures, not due to a congenital or genetic problem, but due to our eating and lifestyle habits. Genetically, we're all programmed to have relatively wide jaws, with room for all your wisdom teeth. Now, that rarely ever happens. This is why obstructive sleep apnea can be described as a mild craniofacial condition that can significantly affect your upper breathing passageways.
Small Jaws, Small Airway
It seems that almost everyone these days will need braces to fix crooked teeth or narrow dental arches. Dental crowding by definition means that your upper and lower jaws are underdeveloped. This creates less total volume inside your mouth, leading to overcrowding of your tongue. Your tongue can then fall back easier when on your back, and when in deep sleep, due to muscle relaxation, you'll stop breathing more often at night.
Even your nose can be affected by this problem. Since your nasal sidewalls follow your upper molars, the side to side distance in your nose will be more narrow, and as the roof of your mouth (nasal floor) gets pushed up, it'll also cause your septum to buckle.
If you add additional inflammation and swelling in your nose (due to colds, allergies or nonallergic rhinitis), your nose will become stuffier faster, and even worse, your nostrils will cave in easier.
Having underdeveloped upper jaws prevents proper cheekbone fullness, giving your mid-face a sinked-in look. This type of facial appearance is so common these days that it's almost accepted as normal. I remember reading in the New York Times a few years back where they reported that women's preferences for male actors has changed from the classic square-faced, angular facial features, to softer, more feminine, rounded faces.