The body of Jamaican children's literature which exists today originated with the oral tradition of folktales that evolved over time. Many Jamaican folktales are based on stories of survival. They were shaped by the culture and history of those who lived through re- and dislocation from Africa, brought to the Caribbean, sold into slavery, and established themselves under British colonial rule in Jamaica. Tales of oral tradition in Jamaica often evolve around overcoming poverty, oppressive power structures, race and class struggles, and surviving the hurdles of life in society. These messages are frequently wrapped in clever form, using comedic animals and trickster types such as Anancy the Spider, John Crow (a vulture), Tukuma, rollin' calves (ghostly characters with eyes like burning coals), or any number of eerie duppies (ghosts) to entertain.