The SWEAT hypothesis, linking the Southwest US and East Antarctica as conjugate rift margins of a Neoproterozoic continent has lead to major revisions of late Precambrian and early Cambrian reconstructions. Geological evidence summarized here supports separation of Antarctica from Laurentia c. 750 Ma ago. A possible link between the break-up of a Neoproterozoic supercontinent and amalgamation of Gondwana during Pan-African times suggests that the Neoproterozoic was a time of rapid tectonic change. This conflicts with those theories that predict regular supercontinental cycles of 500 Ma from the time of disintegration of one supercontinent to its eventual reassembly.