The diversity of NAn languages raises the issue of their possible links with the languages which are now found in Australia. Wurm (1983) has suggested that linguistic traces of an early Australian (or Australoid) population, mixed with later arriving NAn speakers, can be seen in the languages of the Sepik-Ramu Phylum. According to him, Laycock (1973) has pointed out the general resemblance between the phonology of the languages of Ndu Family in the Middle Sepik Stock of the Sepik-Ramu Phylum and the general phonological features of the Australian languages. In addition, the occurrences in the Sepik-Ramu region of Australian cultural elements such as spearthrowers, bullroarers, flat surface and bark painting, and the resemblances of slit-gong melodies to didgeridoo melodies, are all considered to indicate possession of common cultural traits. The connection between the speakers of Sepik-Ramu Phylum languages and Aboriginal Australians has been explained by a southward migration route passing through the Purari River area, possibly because there are similarities between the Sepik art styles and those of the Purari (Spieser 1937), where bullroarers are also found (Williams 1936).
However, further analysis of our data provides no indication of a connection between the Sepik-Ramu populations and Aboriginal Australians via the Purari River area. First, there is no close affinity between the Iatmul (Sepik-Ramu) and the Pawaians (Purari River) (Figure 2). Second, we repeated the analysis of the populations shown in Figure 2 with the inclusion of a population from central Australia (Waljbiri). The resulting network (not illustrated here) shows the Waljbiri are very distantly related to all other populations. The branch leading to the Waljbiri is nearly eight times as long as the next longest terminal branch on the network (leading to Iatmul), and the position at which it connects to the rest of the network could not reliably be determined. It would seem that if there are any genetic affinities underlying the cultural and linguistic similarities between Sepik-Ramu and Australian Aboriginal populations, as discussed by Wurm (1983), these are extremely remote.