Although broken up by Malcolm Ross in 2005, it united different branches of what became TNG for the first time, linking Engan, Chimbu–Wahgi, Goroka, and Kainantu.

Then in 1970, Clemens Voorhoeve and Kenneth McElhanon noted 91 lexical resemblances between the Central and South New Guinea (CSNG) and Finisterre–Huon families, which they had respectively established a few years earlier.

In 1975, Wurm accepted Voorhoeve and McElhanon's suspicions about further connections, as well as Z'graggen's work, and postulated additional links to, among others, the languages of the island of Timor to the west of New Guinea, Angan, Goilalan, Koiarian, Dagan, Eleman, Wissel Lakes, the erstwhile Dani-Kwerba family, and the erstwhile Trans-Fly–Bulaka River family (which he had established in 1970), expanding TNG into an enormous language phylum that covered most of the island of New Guinea, as well as Timor and neighboring islands, and included over 500 languages spoken by some 2,300,000 people.

William A. Foley rejected Wurm's and even some of Voorhoeve's results, and he broke much of TNG into its constituent parts: several dozen small but clearly valid families, plus a number of apparent isolates.

In 2005, Malcolm Ross published a draft proposal re-evaluating Trans–New Guinea, and found what he believed to be overwhelming evidence for a reduced version of the phylum, based solely on lexical resemblances, which retained as much as 85% of Wurm's hypothesis, though some of it tentatively.

However, because of the great morphological complexity of many Papuan languages, and the poor state of documentation of nearly all, in New Guinea this approach is essentially restricted to comparing pronouns.

Because the boundaries of Ross's proposal are based primarily on a single parameter, the pronouns, all internal structure remains tentative.

Ross speculates that the TNG family may have spread with the high population densities that resulted from the domestication of taro, settling quickly in the highland valleys along the length of the cordillera but spreading much more slowly into the malarial lowlands, and not at all into areas such as the Sepik River valley where the people already had yam agriculture, which thus supported high population densities.

Ross suggests that TNG may have arrived at its western limit, the islands near Timor, perhaps four to 4.5 thousand years ago, before the expansion of Austronesian into this area.

[6] ('Family-level' groups are listed in boldface) As of 2003, William A. Foley accepted the core of TNG: "The fact, for example, that a great swath of languages in New Guinea from the Huon Peninsula to the highlands of Irian Jaya mark the object of a transitive verb with a set of verbal prefixes, a first person singular in /n/ and second person singular in a velar stop, is overwhelming evidence that these languages are all genetically related; the likelihood of such a system being borrowed vanishingly small.

In the list given here, the uncontroversial families that are accepted by Foley and other Papuanists and that are the building blocks of Ross's TNG are printed in boldface.

A few of them (Komyandaret, Samarokena, and maybe Kenati) have since been assigned to existing branches (or ex-branches) of TNG, whereas others (Massep, Momuna) continue to defy classification.

[10] Matthew Dryer used lexicostatistics to evaluate Pawley and Hammarström (2018), based on 40-word Swadesh list data from the ASJP database.

[11] Dryer does not consider that evidence based solely on pronouns and the word for 'louse' is sufficient to conclude that a family is a member of Trans-New Guinea.

[11] Dryer notes that this is a preliminary quantitative analysis and only gives a rough prediction of the families that may or may not belong within Trans–New Guinea, and that the lexical similarities it is based on may be due to loanwords, areal forms (Wanderwörter) and so forth.

They have few basic vocabulary items in common with Trans–New Guinea: Timothy Usher and Edgar Suter, in consultation with Papuan language researchers such as William Croft, Matthew Dryer, John Lynch, Andrew Pawley, and Malcolm Ross,[12] have reconstructed low-level constituents of Trans–New Guinea to verify, through the establishment of regular sound changes, which purported members truly belong to it, and to determine their subclassification.

A number of colexification patterns (called 'semantic conflations' by Donald Laycock), particularly in the nominal domain, are commonly found among Trans–New Guinea languages:[9]