A legend is a genre of folklore that consists of a narrative featuring human actions, believed or perceived, both by teller and listeners, to have taken place in human history. Narratives in this genre may demonstrate human values, and possess certain qualities that give the tale verisimilitude. Legend, for its active and passive participants may include miracles. Legends may be transformed over time to keep them fresh and vital. A modern folklorist's professional definition of legend was proposed by Timothy R. Tangherlini in 1990: