Unlike speaking, reading and writing does not come naturally to humans and must be taught. Still literature has been present before the invention of words and language, with 30 000 year old paintings on walls inside some caves portraying a series of dramatic scenes. One of the oldest surviving works of literature is the "Epic of Gilgamesh", first engraved on ancient Babylonian tablets about 4,000 years ago. Beyond simply passing down knowledge the use and sharing of imaginative fiction through stories might have helped develop humans capabilities for communication and increased the likelihood of securing a mate. As well as entertainment, storytelling may also have been used as a way to provide the audience with moral lessons and encourage cooperation.