The origins of the Creatures of Grimm are unknown. Ancient human cultures believed the Grimm were animals possessed by evil spirits, or even the tortured spirits of animals themselves. Further study has disproved this theory over time however, due in part to the discovery of even more horrific misshapen species of Grimm which have no animal counterparts (such as Creeps). With the discovery of new types of Grimm every day, scientists are left with more questions than answers.