The view of Australian languages that has been propagated over the past few decades is that they are all related in a fully specifiable family tree. That is (in terms of the lexicostatistic labels which have been used) each language belongs to a genetic subgroup within a genetic group within a genetic family within the Australian genetic macro-family.

This view cannot be sustained when the proper methodology of comparative and areal linguistics is applied to the Australian situation. Some of what have been suggested as subgroups do appear to have bona fide genetic connections, and a proto-language is likely to be reconstructable for them. Some of what have been suggested as genetic subgroups are in fact small linguistic areas whose member languages appear not to be closely genetically related but to have been in contact for a considerable period and as a result a number of linguistic traits have diffused over the area.

As a sample of the overall situation in Australia, §13.1 briefly surveys a number of likely genetic subgroups, summarising the similarities and differences between their members. In a couple of cases, reconstruction of a fair amount of the proto-language of the subgroup has been completed; in other instances this remains to be done. For a subgrouping to be validated it is, of course, necessary for a good portion of the protolanguage to be reconstructed, together with the systematic changes which have been involved in the development of the modern languages.