Poetry has a long history, dating back to the Sumerian Epic of Gilgamesh. The earliest poems evolved from folk songs, such as the Chinese Shijing, or from the need to retell oral epics, such as the Sanskrit Vedas, Zoroastrian Gathas, and the Homeric epics, the Odyssey and the Iliad. Ancient attempts to define poetry, such as Aristotle's Poetics, focused on the uses of speech in rhetoric, drama, song, and comedy. Later attempts concentrated on features such as repetition, verse form and rhyme, and emphasized the aesthetics which distinguish poetry from more objectively informative, prosaic forms of writing. From the mid-20th century, poetry has sometimes been more generally labelled as a fundamental creative act using language.