The presence of a sturdy chin, or lack thereof, always has and always will be predicated on a fighter's genealogical makeup.
And since a chin can't be strengthened through hard work and dedication, those seemingly blessed with jaws of granite bring an attribute to the cage that many fighters can only dream of possessing.
The opening portion of this two-part slideshow details the most rock-solid chins in MMA history—those that withstood countless beatings before ever giving into an embarrassing in-fight nap.
The second segment represents a list of the most unreliable chins in the sport's history, a countdown of glass-jawed warriors who couldn't seem to survive in slugfests.
