Aesop's Fables or the Aesopica is a collection of fables credited to Aesop, a slave and story-teller believed to have lived in ancient Greece between 620 and 560 BC. Aesop was a story teller credited with a number of fables now collectively known as Aesop's Fables. Although his existence remains uncertain and no writings by him survive, numerous tales credited to him were gathered across the centuries and in many languages in a storytelling tradition that continues to this day. In many of the tales, animals speak and have human characteristics. Scattered details of Aesop's life can be found in ancient sources, including Aristotle, Herodotus, and Plutarch. An ancient literary work called The Aesop Romance tells an episodic, probably highly fictional version of his life, including the traditional description of him as a strikingly ugly slave who by his cleverness acquires freedom and becomes an adviser to kings and city-states.