What we colloquially refer to as "aging" is a process by which human bodies gradually degrade over time, with physical manifestations including a greying of the hair and a loss of elasticity in the skin. Some people believe that it is caused by free radicals breaking down body cells. Others believe that the aging is a function of the body which was selected for via natural selection. Still others believe that it is the natural result of being a lying Muslim atheist communist fascist who is secretly the gay Antichrist.

Sources: Diran Lyons | h/t BuzzFeed