At a particular point (yet to be clearly defined) in human cultural evolution, a specific idea took hold that there were two, partially separable, elements present in a living creature: the material body and the force that animated it. On the death of the body the animating force would, naturally, desire the continuation of this-worldly action and struggle to reassert itself (just as one might strive to retrieve a flint axe one had accidentally dropped). If the soul (or spirit) succeeded, it would also seek to repossess its property, including its spouse, and reassert its material appetites.
The desire of the disembodied soul was viewed as dangerous by the living, who had by all means to enchant, cajole, fight off, sedate, or otherwise distract and disable it. This requirement to keep the soul from the body after death did not last forever, only so long as the flesh lay on the bones. For the progress of the body's decomposition was seen as analogous to the slow progress the soul made toward the threshold of the Otherworld. When the bones where white (or were sent up in smoke or whatever the rite in that community was), then it was deemed that the person had finally left this life and was no longer a danger to the living. Thus it was, that for most of recent human history (roughly the last 35,000 years) funerary rites were twofold: the primary rites zoned off the freshly dead and instantiated the delicate ritual powers designed to keep the unquiet soul at bay; the secondary rites, occurring after weeks or months (or, sometimes — in the case of people who had wielded tremendous worldly power — years), firmly and finally incorporated the deceased into the realm of the ancestors.
Since the rise of science and scepticism, the idea of the danger of the disembodied soul has, for an increasing number of communities, simply evaporated. But there is a law of conservation of questions. "How can I stop the soul of the deceased reanimating the body?" is now being replaced with "How can I live so long that my life becomes indefinite?," a question previously only asked by the most arrogant pharaohs and emperors.
TIMOTHY TAYLOR lecturers in the Department of Archaeological Sciences, University of Bradford, UK. He is the author of The Prehistory of Sex.