Shamanic rituals constitute the most important social events in hunter-gatherer societies, structuring the relationships of individuals to the collectivity and cosmology. The shamans’ spirit encounters are basic to their societies’ cosmology, hunting practices, and ecological and community relations and healing. The shaman heals patients through the recovery of their souls or personal power, or by removing negative influences sent by spirits or sorcerers. Shamans are assisted in their professional tasks by their allies and guardians, generally animal spirits acquired during arduous training.