In the early twentieth century, the traditional religions of the Yoruba altered significantly as a result of European rule. Where the modes of worship conflicted with Western mores the ruling colonial powers placed restrictions on religious practice, The white rulers accused the Shokpona priests of spreading smallpox in order to keep their power and so outlawed the cult even before the use of smallpox vaccine. Night gatherings, so vital to the worship of Ogun and the parctice of Ifa, were severely restricted. The marriage customs of the Yoruba permitted polygamy and incestuous marriages, as well as the practice of marrying a dead male relative's widow and adopting his childrem. These customs were banned. Europeans also insisted upon burying the dead in communal graveyards rather than the traditional Yoruba practice of burying them in the house, thus interfering with communion between the Yoruba and their dead relatives.