A sangoma is a practitioner of herbal medicine, divination and counselling in traditional Nguni (Zulu, Xhosa, Ndebele and Swazi) societies of Southern Africa (effectively an African shaman). The philosophy is based on a belief in ancestral spirits. Both men and women can be called by the ancestors (a consequence of refusing the calling is usually ongoing physical or mental illness) though sangomas are usually female. Historically the sangoma role has been the preserve of the black, indigenous peoples of Africa, but post-Apartheid white South Africans have also entered the profession - John Lockley is reputedly one of the first white men in recent history to become a fully initiated Xhosa sangoma. A trainee sangoma (or twaza) trains under another sangoma, usually for a period of years, usually performing humbling service in the community. At times in the training, and for the graduation, a ritual sacrifice of an animal is performed (usually a chicken, a goat or a cow). The spilling of this blood is meant to seal the bond between the ancestors and the sangoma.