Trans–New Guinea (TNG) is an extensive family of Papuan languages spoken on the island of New Guinea and neighboring islands, a region corresponding to the country Papua New Guinea as well as parts of Indonesia.

Trans–New Guinea is perhaps the third-largest language family in the world by number of languages. The core of the family is considered to be established, but its boundaries and overall membership are uncertain. The languages are spoken by around 3 million people. There have been several main proposals as to its internal classification.

History of the proposal Although Papuan languages for the most part are poorly documented, several of the branches of Trans–New Guinea have been recognized for some time. The Eleman languages were first proposed by S. Ray in 1907, parts of Marind were recognized by Ray and JHP Murray in 1918, and the Rai Coast languages in 1919, again by Ray.

The precursor of the Trans–New Guinea family was Stephen Wurm's 1960 proposal of an East New Guinea Highlands family. 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. (Duna and Kalam were added in 1971.) 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. Although they did not work out regular sound correspondences, and so could not distinguish between cognates due to genealogical relationship, cognates due to borrowing, and chance resemblances, their research was taken seriously. They chose the name Trans–New Guinea because this new family was the first to span New Guinea, from the Bomberai Peninsula of western West Irian to the Huon Peninsula of eastern PNG. They also noted possible cognates in other families Wurm would later add to TNG: Wurm's East New Guinea Highlands, Binandere in the 'Bird's Tail' of PNG, and two families that John Z'graggen would later (1971, 1975) unite in his 100-language Madang–Adelbert Range family.

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. However, part of the evidence for this was typological, and Wurm stated that he did not expect it to stand up well to scrutiny. Although he based the phylum on characteristic personal pronouns, several of the branches had no pronouns in common with the rest of the family, or even had pronouns related to non-TNG families, but were included because they were grammatically similar to TNG. Other families that had typical TNG pronouns were excluded because they did not resemble other TNG families in their grammatical structure.

Given that grammatical typology is readily borrowed – many of the Austronesian languages in New Guinea have grammatical structures similar to their Papuan neighbors, for example, and conversely many Papuan languages resemble typical Austronesian languages typologically –, other linguists were skeptical. 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.

The strongest lexical evidence for any language family is shared morphological paradigms, especially highly irregular or suppletive paradigms with bound morphology, because these are extremely resistant to borrowing. For example, the fact that the German words gut "good" and besser "better" resemble their English counterparts is stronger evidence that German is related to English than the mere lexical correspondence between German rot and English red for the color. 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. Ross (as a first step) reconstructed pronoun sets for Foley's basic families and compared these reconstructions, rather than using a direct mass comparison of all Papuan languages, (as a second step) attempted to then reconstruct the ancestral pronouns of the Proto-Trans–New Guinea language, such as *ni "we", *ŋgi "you", *i "they", and (as a third step) then compared poorly supported branches directly to this reconstruction. Families required two apparent cognates to be included. However, if any language in a family was a match, the family was considered a match, greatly increasing the likelihood of coincidental resemblances, and because the plural forms are related to the singular forms, a match of 1sg and 1pl, although satisfying Ross's requirement of two matches, is not actually two independent matches, again increasing the likelihood of spurious matches. In addition, Ross counted forms like *a as a match to 2sg *ga, so that all counted as matches to *ga. And although and occur in Papuan pronouns at twice the level expected by their occurrence in pronouns elsewhere in the world, they do not correlate with each other as they would if they reflected a language family. That is, it is argued that Ross's pronouns do not support the validity of Trans–New Guinea, and do not reveal which families might belong to it.Harald Hammarström (2012) "Pronouns and the (Preliminary) Classification of Papuan languages", Journal of the Linguistic Society of Papua New Guinea

Ross also included in his proposal several better-attested families for non-pronominal evidence, despite a lack of pronouns common to other branches of TNG, and he suggested that there may be other families that would have been included if they had been better attested. Several additional families are only tentatively linked to TNG. Because the boundaries of Ross's proposal are based primarily on a single parameter, the pronouns, all internal structure remains tentative.

The languages

Most TNG languages are spoken by only a few thousand people, with only seven (Melpa, Kuman, Enga, Huli, Western Dani, Makasae, and Ekari) being spoken by more than 100,000. The most populous language outside of mainland New Guinea is Makasae of East Timor, with 100,000 speakers throughout the eastern part of the country. Enga is the most populous Trans-New Guinea language spoken in New Guinea, with more than 200,000 speakers. Golin, Sinasina, Central Grand Valley Dani, Kamano, and Bunaq have between 50,000 and 100,000 speakers (Galela of Halmahera, usually not classified as Trans-New Guinea, also has between 50,000 and 100,000 speakers.) All other Trans–New Guinea languages have fewer than 50,000 speakers.

The greatest linguistic diversity in Ross's Trans–New Guinea proposal, and therefore perhaps the location of the Trans–New Guinea homeland, is in the interior highlands of Papua New Guinea, in the central-to-eastern New Guinea cordillera, just where Wurm first posited his East New Guinea Highlands family. Indonesian Papua and the Papuan Peninsula of Papua New Guinea (the "bird's tail") have fewer and more widely extended branches of TNG, and were therefore likely settled by TNG speakers after the proto-language broke up.

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. Roger Blench associates the spread of Trans–New Guinea languages with the domestication of the banana.Roger Blench (2017) "Things your classics master never told you: a borrowing from Trans New Guinea languages into Latin", McDonald Institute for Archaeological Research

Classification Wurm, Voorhoeve & McElhanon (1975) Wurm et al. identify the subdivisions in their Papuan classification as families (on the order of relatedness of the Germanic languages), stocks (on the order of the Indo-European languages), and phyla (on the order of the Nostratic hypothesis). Trans-New Guinea is a phylum in this terminology. A language that is not related to any other at a family level or below is called an isolate in this scheme.S.A.Wurm, C.L.Voorhoeve & K. McElhanon, The Trans-New Guinea Phylum in General. Section 2.5 of S.A. Wurm (ed.) 1977 New Guinea Area Languages and Language Study, Volume 1: Papuan Languages and the New Guinea Linguistic Scene. Australian National University, Canberra

('Family-level' groups are listed in boldface)

?Oksapmin isolate [inclusion dubious] Morwap isolate Molof isolate Usku isolate Tofamna isolate Eleman stock Eleman family Purari isolate (Koriki, Namau) Tate isolate Inland Gulf stock Ipiko isolate Minanibai family (incl. Karami) Kaure stock Kaure family Kapori isolate Sause isolate Kolopom (Frederik Hendrik Island) family Nimboran family Goliath family (Mek) Northern, or Border–Tor–Lake Plain super-stock Border stock Waris family Taikat family Bewani family Tor – Lake Plain stock Tor family Turu family Central Lake Plain family Uria isolate Mawes isolate Pauwasi stock Eastern family Western family (Dubu, Towei) Senagi family South Bird's Head (Vogelkop) stock South Bird's Head family Inanwatan family Konda–Yahadian family Timor–Alor–Pantar stock Bunak isolate Makasai isolate Oirata isolate Fataluku (Dagodá) isolate Lovaea isolate Kairui isolate Alor–Pantar family Teberan–Pawaian superstock Teberan family Pawaia isolate Turama–Kikorian stock Mena or Turama–Omatian family Kairi (Dumu) isolate Trans-Fly – Bulaka River superstock Bulaka River family (Yelmek–Maklew) Trans-Fly stock Kiwaian family Tirio family Eastern Trans-Fly family Pahoturi River family Morehead & Upper Maro Rivers family: Nambu subfamily Tonda subfamily Yey isolate Moraori isolate Madang – Adelbert Range subphylum Madang superstock Rai Coast stock Evapia family (Asas, Dumpu, Kesawai, Sausi, Sinsauru) Mindjim family Kabenau family (Arawum, Kolom, Siroi, Lemio, Pulabu) Yaganon family Peka family (Usino, Sumau, Urigina, Danaru) Nuru family (Usu, Erima, Duduela, Kwato, Rerau, Jilim, Yangulam) Mabuso stock Kare isolate Kokon family Gum family Hanseman family Adelbert Range superstock Mugil isolate Isumrud stock Dimir isolate Kowan family Mabuan family Pihom stock Amaimon isolate Kaukombaran family Kumilan family Numagenan family Omosan family Tiboran family Josephstaal stock Osum isolate Wadaginam isolate Sikan family Pomoikan family Wanang stock Paynamar isolate Atan family (Atemble, Angaua) Emuan family (Emerum, Musak) Brahman family (membership per Z'graggen) Main Section: Eastern TNG subphylum Binandere stock Guhu-Semane isolate Binandere family Goilalan family Koiarian family Kwalean family Manubaran family Yareban family Mailuan family