The Indo-Pacific proposal, grouping the non-Austronesian languages of New Guinea with certain languages spoken on islands to the east and west of New Guinea, was first made by Greenberg in 1971. Greenberg's supporter Merritt Ruhlen considers Indo-Pacific an extremely diverse and ancient family, far older than Austronesian, which reflects a migration from southeast Asia that began only 6,000 years ago; he notes that New Guinea was inhabited by modern humans at least 40,000 years ago, and possibly 10,000 to 15,000 years earlier than that.Luigi Luca Cavalli-Sforza sees Indo-Pacific as a very heterogenous family of 700 languages and suggests that it may be more than 40,000 years old.
Greenberg's proposal was based on rough estimation of lexical similarity and typological similarity and has not reached a stage where it can be confirmed by the standard comparative method, including the reconstruction of a protolanguage. The languages of Tasmania are extinct and so poorly attested that many historical linguists regard them as unclassifiable. Roger Blench has dismissed the Indo-Pacific proposal as improbable, observing that while it "purported to be a purely linguistic exercise...it conveniently swept up all the languages of the crinklyhaired populations in the region that were not clearly Austronesian." He writes that despite decades of further research into Papuan languages and prehistory, Indo-Pacific is still not accepted by specialists and that it "only exists in the eye of the believer."George van Driem (2001) responds as follows:
Racial notions have continued to be uncritically applied to language groupings. As late as 1971, Joseph Greenberg resurrected the old idea that "the bulk of non-Austronesian languages of Oceania from the Andaman Islands on the west of the Bay of Bengal to Tasmania in the Southeast form a single group of genetically related languages for which the name Indo-Pacific is proposed." This hypothesis is identical to Finck's 1909 family of "Sprachen der ozeanischen Neger", a group for which indeed the name "Indo-Pacific" had already been in use, with its roots in the "Pan-Negrito Theory" of physical anthropologists (cf. Skeat and Blagden 1906: 25–28). Appropriately, Roger Blench has described the Indo-Pacific hypothesis as "essentially a crinkly hair hypothesis".
The linguistic evidence which Greenberg adduced for Indo-Pacific is unconvincing, and lexical look-alikes and superficial typological similarities in languages cannot convincingly demonstrate a theory of linguistic relationships conceived solely on the basis of the physical attributes of the speakers.
Since Greenberg's work, the languages of New Guinea have been intensively studied by Stephen Wurm. Wurm's Trans–New Guinea languages family includes about 70 percent of the languages Greenberg included in Indo-Pacific, though the internal classification is entirely different. Wurm states that the lexical similarities between Great Andamanese, West Papuan (which is not part of Trans–New Guinea), and certain languages of Timor "are quite striking and amount to virtual formal identity […] in a number of instances", but considers this to be due to a linguistic substratum rather than a direct relationship.
Pawley (2008) is the only thorough review of the proposal. He found that all branches of Indo-Pacific except Tasmanian and Andamanese include languages from Trans–New Guinea, and that this explains the more reasonable cognates that Greenberg proposed, but because these Trans–New Guinea languages are mixed in with languages from other families in those branches, cognates linking the branches do not provide support for Greenberg's proposal that all Papuan languages are related.
According to Greenberg, Indo-Pacific consists of fourteen families, not counting a few which he could not classify. He suggested a tentative sub-classification into seven groups, listed in bold below. Some languages have not been identified.
^Identified with Jimajima (Dagan family) by Glottolog, but this contradicts the location in Ray.
Greenberg, Joseph H. 1971. "The Indo-Pacific hypothesis." In Current Trends in Linguistics, Vol. 8: Linguistics in Oceania, edited by Thomas A. Sebeok, 808-71. The Hague: Mouton. (Reprinted in Greenberg, Genetic Linguistics, 2005, 193–275.) Family tree available at the Linguist List MultiTree Project [no longer functional as of 2014]
Greenberg, Joseph H. 2005. Genetic Linguistics: Essays on Theory and Method, edited by William Croft. Oxford: Oxford University Press.