The study of the human body is one of the oldest of sciences, being considered necessary not only for the advancement of medicine, but also for the creation of realistic artworks. Up until the Renaissance, most Western theories of Anatomy were from the Greek author Galen, whose knowledge of the inner workings of the human body was mostly hearsay and based on comparison to monkeys. Rogue anatomists of the Renaissance found errors in Galen while illegally dissecting corpses. Eventually, religious restrictions against such practices were lifted, and now the workings of the human body are something we are all familiar with.