Everything we know about the Greek philosopher Pythagoras (ca. 580 B.C.- ca. 490 B.C. - he died when he was 90 years old!) comes from those who lived many years after him, and fortunately, his philosophy of vegetarianism is beautifully memorialized in Ovid's great epic poem, The Metamorphoses. Early vegetarians were called "Pythagoreans," and 2,500 years after his death, his admonitions against slaughtering animals for human consumption still ring true.