Who inherits what, when?

There has been much discussion on the kinds of linguistic traits that can be borrowed, and under what circumstances, and the relationship of different kinds of contact to areality. This article suggests that phonological aberrancies, in terms of the family to which a language belongs, in the core phonology are indicative of an older substrate, while morphosyntactic aberrancies indicate superimposition. A case study of Australian phonological systems is analyzed in terms of the typology presented, which when correlated with other nonlinguistic evidence reveals insights into human prehistory in that continent.