In the 1970s Australian linguist [[Donald Laycock]] classified Tayap (which he called "[[Gapun]]") as a sub-phylum of the Sepik-Ramu language phylum, on the basis of Georg Höltker's 1938 word list and a few verb paradigms that Laycock gathered from two speakers.<ref>{{harvp|Laycock|1973}}</ref>
Kulick and Terrill (2019) found no evidence that Tayap is related to the Lower Sepik languages, another branch of the erstwhile Sepik-Ramu phylum. TheThey conclude that Tayap is a [[language isolate]], though they do not compare it to other language families, as would be required to establish Tayap as an independent language family. Comparative vocabulary demonstrates the lexical aberrancy of Tayap as compared to the surrounding Lower Sepik languages: e.g. ''sene'' 'two' (cf. [[proto-Lower Sepik]] *ri-pa-), ''neke'' 'ear' (*kwand-), ''ŋgino'' 'eye' (*tambri), ''tar'' 'hear' (*and-), ''min'' 'breast' (*nɨŋgay), ''nɨŋg'' 'bone' (*sariŋamp), ''malɨt'' 'tongue' (*minɨŋ), ''mayar'' 'leaf' (*nɨmpramp) among the Holman ''et al.'' (2008) ranking of the [[Swadesh list]]. Cultural vocabulary such as 'village', 'canoe', 'oar', and 'lime', as well as the basic words ''awin'' 'water' (cf. *arɨm) and ''a'' 'eat' (cf. *am ~ *amb), may be shared with Lower Sepik languages. The word ''karep'' 'moon' is shared specifically with [[Kopar language|Kopar]] (''karep''). However, most basic vocabulary items have no apparent cognates in surrounding languages.<ref name="Foley-Sepik-Ramu">{{Cite book |last=Foley |first=William A. |title=Papuan Pasts: Cultural, Linguistic and Biological Histories of Papuan-Speaking Peoples |date=2005 |publisher=Pacific Linguistics |isbn=0-85883-562-2 |editor-last=Pawley |editor-first=Andrew |editor-link=Andrew Pawley |series=Pacific Linguistics 572 |___location=Canberra |pages=109–144 |language=en |chapter=Linguistic Prehistory in the Sepik-Ramu Basin |hdl=1885/146735 |author-link=William A. Foley |editor-last2=Attenborough |editor-first2=Robert |editor-last3=Hide |editor-first3=Robin |editor-last4=Golson |editor-first4=Jack |hdl-access=free}}</ref>
