Affinities among Melanesians, Micronesians, and Polynesians: A neutral, biparental genetic perspective

Human Biology, Jun 2002 by Lum, J Koji, Jorde, Lynn B, Schiefenhovel, Wulf

Abstract The human colonization of Remote Oceania, the vast Pacific region including Micronesia, Polynesia, and Melanesia beyond the northern Solomon Islands, ranks as one of the greatest achievements of prehistory. Many aspects of human diversity have been examined in an effort to reconstruct this late Holocene expansion. Archaeolinguistic analyses describe a rapid expansion of Austronesian-speaking "Lapita people" from Taiwan out into the Pacific. Analyses of biological markers, however, indicate genetic contributions from Pleistocene-settled Near Oceania into Micronesia and Polynesia, and genetic continuity across Melanesia. Thus, conflicts between archaeolinguistic and biological patterns suggest either linguistic diffusion or gene flow across linguistic barriers throughout Melanesia. To evaluate these hypotheses and the general utility of linguistic patterns for conceptualizing Pacific prehistory, we analyzed 14 neutral, biparental genetic (short tandem repeat) loci from 965 individuals representing 27 island Southeast Asian, Melanesian, Micronesian, and Polynesian populations. Population bottlenecks during the colonization of Remote Oceania are indicated by a statistically significant regression of loss of heterozygosity on migration distance from island Southeast Asia (r = 0.78, p 0.35, p

KEY WORDS: MELANESIA, MICRONESIA, POLYNESIA, OCEANIA, STR, GENE FLOW, LANGUAGE

Human settlement of the Pacific began with the colonization of New Guinea 40-60,000 years before present (BP) (Groube et al. 1986). By 29,000 BP all the large, intervisible islands as far as the northern Solomons were inhabited (Wickler and Spriggs 1988). This western Melanesian region of Pleistocene colonization known as Near Oceania (Pawley and Green 1973; Green 1991; Green 1999) is also the eastern limit of Papuan-speaking people in the Pacific. Further expansion into the Pacific began within the last 3500 BP and is associated archaeologically with the Lapita cultural complex and linguistically with the Austronesian language family (Bellwood 1985; Kirch 1997; Kirch 2000). Lapita sites dated between 3500 and 3000 BP are found in the Bismarcks (Kirch 1987), the Solomons (Green 1976), Vanuatu (Hedrick 1971), Fiji (Davidson and Leach 1993), Tonga (Poulsen 1987), and Samoa (Green and Davidson 1974). The presence of pottery with nearly identical form and design motifs distributed on islands spread across 4500 kilometers of the Pacific dated within 500 years suggests an initial colonization of Remote Oceania by a single population or closely related populations with a shared culture (Kirch and Hunt 1988; Kirch 1997; Kirch 2000). By 1000 BP all of the major island groups of eastern Melanesia, Micronesia, and Polynesia, collectively known as Remote Oceania (Pawley and Green 1973; Green 1991; Green 1999), had been colonized (Spriggs and Anderson 1993; Intoh 1997). All of the populations of Remote Oceania speak Austronesian languages, and all except the people of the Marianas and Palau in Western Micronesia speak Oceanic languages, a lower-order branch of the Austronesian language family (Bender 1971; Pawley and Green 1973; Pawley and Ross 1993; Ross 1996). Thus, the restriction of Papuan languages within Pleistocene-settled Near Oceania and the distribution of Austronesian languages throughout Holocene-settled Remote Oceania suggest the colonization of these regions by distinct populations. The concordance among settlement time, geographic region, and language family coupled with the comprehensive classification of approximately 750 Papuan and 770 Austronesian languages (Foley 1992; Clark 1992) has resulted in the general use of linguistic patterns as the null hypothesis of Pacific human diversity.

Much of the debate about the origins of Remote Oceanic islanders concerns the relative contributions to the region from Asia and Near Oceania. An intrusive expansion of people from Asia into Remote Oceania is suggested by both linguistic and archaeological patterns. The Austronesian languages of Remote Oceania are thought to have originated in Taiwan within the last 5000 to 6000 years (Blust 1981; Bellwood 1985; Blust 1995). Similarly, Kirch (2000) believes that although Lapita pottery originated in the Bismarcks, it was an outgrowth of similar ceramic traditions found in Indonesia and Taiwan dated to 4000 BP and 4500 BP, respectively. Thus, the languages and defining material culture of the initial settlement of Remote Oceania are both inferred to result from a recent cultural expansion out of Taiwan (Bellwood 1985; Bellwood 1987; Diamond 1988; Kirch 1997; Kirch 2000).

If Remote Oceania was settled by Austronesian-speaking "Lapita people" originating in Taiwan, biological markers are expected to group Austronesianspeaking Melanesians, Micronesians, Polynesians, and Asians to the exclusion of Near Oceanic populations. Although analyses of morphological traits do group Asians, Micronesians, and Polynesians together, Oceanic Austronesian-speaking Melanesians cluster with Near Oceanic, Papuan-speaking Melanesians and Aboriginal Australians (Pietrusewsky 1990a; Pietrusewsky 1990b; Hanihara 1993). Likewise, analyses of mitochondrial DNA (mtDNA) polymorphisms reveal that the majority of lineages from Micronesian and Polynesian populations belong to a monophyletic clade characterized by the region V deletion (Cann and Wilson 1983) derived from East Asia (Hertzberg et al. 1989; Lum et al. 1994; Redd et al. 1995; Sykes et al. 1995; Hagelberg et al. 1999; Lum and Cann 1998; Lum et al. 1998; Lum and Cann 2000). Although ultimately of Asian origin, the most common region-V-deleted sequences of Remote Oceanic populations belong to lineage group I.1 (Lum et al. 1994; Lum and Cann 2000), also called the "Polynesian Motif' (Redd et al. 1995), thought to be derived proximally from Indonesia (Richards et al. 1998; Lum and Cann 2000; Oppenheimer and Richards 2001). The region V deletion cluster is also found within Austronesian-speaking Melanesian populations (and some of their Papuan-speaking neighbors), but in highly variable frequencies (Hertzberg et al. 1989; Sykes et al. 1995; Lum and Cann 1998; Lum and Cann 2000; Hagelberg et al. 1999; Merriwether et al. 1999). These data suggest extensive prehistoric gene flow among Austronesian- and Papuan-speaking Melanesian populations. Recent Y-chromosome analyses have distinguished Southeast Asia as the region of highest paternal genetic diversity. In these studies, North Asian and Pacific populations are seen as distinct subsets of Southeast Asian diversity (Su et al. 2000; Capelli et al. 2001). Moreover, eastern Indonesian, Micronesian, Polynesian, and both Papuan- and Austronesian-speaking Melanesian populations share a similar haplotype distribution (Kayser et al. 2000; Kayser et al. 2001). These data support a Melanesian (or eastern Indonesian) origin of Remote Oceanic Y chromosomes (Underhill et al. 2001), leading Capelli et al. (2001) to suggest diffusion of memes rather than genes as the origin of Austronesian languages within Melanesia and other regions of Remote Oceania. This assertion is contra maternally inherited mtDNA affinities that are generally correlated with linguistic relationships among Austronesian-speaking populations (Lum and Cann 1998), particularly those of Melanesia and Polynesia (Lum et al. 1998). These inconsistent associations between linguistic and paternally or maternally inherited genetic patterns can be reconciled either by linguistic diffusion or a male-biased "Gene Flow" model of Remote Oceanic prehistory (Lum et al. 1998; Delvin et al. 2001).