The history of popular religion in Scotland includes all forms of the formal theology and structures of institutional religion, between the earliest times of human occupation of what is now Scotland and the present day. Very little is known about religion in Scotland before the arrival of Christianity. It is generally presumed to have resembled Celtic polytheism and there is evidence of the worship of spirits and wells. The Christianisation of Scotland was carried out by Irish-Scots missionaries, and to a lesser extent those from Rome and England, from the sixth century. Elements of paganism survived into the Christian era. Most early evidence of religious practice is heavily biased towards monastic life. Priests carried out baptisms, masses and burials, prayed for the dead and offered sermons. The church dictated in moral and legal matters and impinged on other elements of everyday life through its rules on fasting, diet, the slaughter of animals and rules on purity and ritual cleansing. One of the main features of Medieval Scotland was the Cult of Saints, with shrines devoted to local and national figures, including St Andrew, and the establishment of pilgrimage routes.