When did Muhammad Ali start boxing?

In 1954 in Louisville, Kentucky, 12-year-old Cassius Marcellus Clay's bike was stolen while he and a friend were at the Columbia Auditorium. Young Cassius found a cop in a gym, Joe Martin, and boiling with youthful rage, told Martin he was going to "whup" whoever stole his bike. Martin admonished, "You better learn to box first." Within weeks, 89-pound Cassius had his first bout-his first win. For the next 27 years, Cassius would be in that ring. Even in his youth, he had dreams of being heavyweight champion of the world. But his life would take turns that no seer could've predicted.