  We introduce a novel mechanism where processes that preserve the number
density of the dark sector set the relic density of a thermal particulate dark
matter. In a relatively degenerate multipartite dark sector if there is a
considerable time lapse between the freeze out of various species then a
process like exchange between dark sector constituents can play the pivotal
role of driving freeze out and setting dark matter relic density. As a proof of
principle, we present simple scalar models with viable dark matter in the GeV
scale to demonstrate this phenomenon.
