The Osu caste system in Nigeria and southern Cameroon of the Igbo people can be traced back to Odinani, the traditional Igbo religion. It is the belief of many Igbo traditionalists that the Osus are people historically owned by deities, and are therefore considered to be a 'living sacrifice', an outcast, untouchable and sub-human (similar to the Roman practice of "homo sacer"). This system received literary attention when it became a key plot point in "No Longer at Ease" by Chinua Achebe.