Inspired by this Scientific American Blog Article.
To summarize the article:
The upshot: the universal consciousness can dissociate from itself into fragments i.e. the universal consciousness is a massively polyfragmented system.
The article takes the point-of-view of several scientific theories that have problems explaining individual consciousness or combining lower levels of "consciousness" into larger systems of consciousness. The article glances at dissociation in DID as evidence of the mechanism that the universal consciousness splits into discrete individual pockets of consciousness; 1 consciousness per body for singlets, many per body for multiples.
In this view, whatever "inspired" one's body's consciousness or collections thereof to be one or several is immaterial to the theory itself; you may have many consciousnesses in one physical body.