Groping for an explanation of the world around them, the earliest humans developed the first concepts of religion. Gradually, rites of worship grew to include sacrifices, ceremonies, vigils, symbology, sacred items, and prayer. One significant step in the advance of worship was the ceremonial burial, often a ritual preparation of the deceased's body for the afterlife his or her culture anticipated. The remains of ceremonial burials offer some of the most detailed information about past civilizations.