AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 000:000–000 (2006) Skin and Hair Pigmentation Variation in Island Melanesia Heather L. Norton,1 Jonathan S. Friedlaender,2 D. Andrew Merriwether,3 George Koki,4 Charles S. Mgone,4 and Mark D. Shriver1* 1Department of Anthropology, Pennsylvania State University, University Park, Pennsylvania 16802 2Department of Anthropology, Temple University, Philadelphia, Pennsylvania 19122 3Department of Anthropology, State University of New York at Binghamton, Binghamton, New York 13901 4Papua New Guinea Institute for Medical Research, Goroka, Eastern Highlands Province 441, Papua New Guinea KEY WORDS skin pigmentation; M index; Island Melanesia; natural selection ABSTRACT Skin and hair pigmentation are two of tation was significantly darker than females in 5 of 6 the most easily visible examples of human phenotypic islands examined. Hair pigmentation showed a negative, variation. Selection-based explanations for pigmentation but weak, correlation with age, while skin pigmentation variation in humans have focused on the relationship be- showed a positive, but also weak, correlation with age. tween melanin and ultraviolet radiation, which is largely Skin and hair pigmentation varied significantly between dependent on latitude. In this study, skin and hair pig- islands as well as between neighborhoods within those mentation were measured as the melanin (M) index, us- islands. Bougainvilleans showed significantly darker skin ing narrow-band reflectance spectroscopy for 1,135 indi- than individuals from any other island considered, and viduals from Island Melanesia. Overall, the results show are darker than a previously described African-American remarkable pigmentation variation, given the small geo- population. These findings are discussed in relation to graphic region surveyed. This variation is discussed in prevailing hypotheses about the role of natural selection terms of differences between males and females, among in shaping pigmentation variation in the human species, islands, and among neighborhoods within those islands. as well as the role of demographic processes such as ad- The relationship of pigmentation to age, latitude, and lon- mixture and drift in Island Melanesia. Am J Phys An- gitude is also examined. We found that male skin pigmen- thropol 000:000–000, 2006. VC 2005 Wiley-Liss, Inc. The human species shows remarkable variation in for the general trend toward lighter skin pigmentation both skin and hair pigmentation. Both traits, and partic- in low UVR regions, and recent work by Jablonski and ularly skin pigmentation, have commonly been used as a Chaplin (2000) strengthened the case for it. tool to classify individuals into discrete racial groups. This paper examines pigmentation variation in Island However, a closer inspection shows that humans cannot Melanesia, an equatorial area renowned for its biological be so neatly categorized. Skin pigmentation, despite and linguistic diversity (Fig. 1). The peopling of Island often being synonymous with racial taxonomies, shows Melanesia and the larger region of Oceania has been substantial variation within human populations and studied from linguistic, archaeological, and biological within regional groupings or ‘‘races.’’ Pigmentation var- perspectives. While each of these approaches has re- iation within and among populations has been explained vealed particular aspects of the history of human migra- as the result of either natural selection (e.g., Cowles, tions in this region, a synthesis has begun to emerge 1959; Wasserman, 1965; Loomis, 1967; Walter, 1971; concerning the outlines of modern human dispersals in Post et al., 1975; Branda and Eaton, 1978; Jablonski and Island Melanesia. Human populations had expanded Chaplin, 2000; Mackintosh, 2001) or sexual selection across the Old World and into Australia by 50,000 BP (Darwin, 1871; Diamond, 1988, 1992; Frost, 1988). Selec- (Roberts et al., 1994; Bowler et al., 2003). The earliest tion-based hypotheses have focused on the relationship human presence in New Guinea can be dated to at least between skin pigmentation and ultraviolet radiation 40,000 BP, while recent estimates for the earliest occupa- (UVR) (Walter, 1971; Relethford, 1997; Jablonski and tion of the Bismarck Archipelago (namely New Ireland) Chaplin, 2000; Chaplin, 2004). High levels of UVR can lead to skin damage such as sunburn or skin cancer, as well as the breakdown of folic acid (Branda and Eaton, Grant sponsor: Wenner Gren Foundation for Anthropological 1978). As melanin provides some protection from UVR- Research; Grant sponsor: National Geographic Exploration Fund; induced damage (e.g., Pathak and Fitzpatrick, 1974; Kol- Grant sponsor: National Science Foundation; Grant sponsor: Pennsyl- vania State University. lias et al., 1991; Sheehan et al., 2002), a compelling selectionist argument is that darkly melanized skin is an *Correspondence to: Mark Shriver, Department of Anthropology, adaptation in regions of high UVR. While photodamage Pennsylvania State University, 409 Carpenter Building, University and nutrient photolysis may not be very strong selective Park, PA 16802. E-mail: [email protected] pressures in regions where UVR is low, these regions present their own challenges. Specifically, it was sug- Received 5 August 2004; accepted 4 May 2005. gested that lighter pigmentation in these regions may have been an adaptation to ensure the production of suf- DOI 10.1002/ajpa.20343 ficient levels of vitamin D3 in the skin (Murray, 1934; Published online in Wiley InterScience Loomis, 1967). This is a commonly accepted explanation (www.interscience.wiley.com). VC 2005 WILEY-LISS, INC. 2 H.L. NORTON ET AL. Fig. 1. Map of study region in Island Melanesia. Samples were obtained from islands of New Guinea, New Britain, New Ire- land, Mussau, New Hanover, and Bougainville (asterisked). are also at around 40,000 years BP (Leavesley et al., isolation accompanying these changes would be expected 2002), implying sailing capabilities at that time. These to increase, or at least maintain, genetic diversity across dates for human occupation at New Ireland suggest an the region. even earlier settlement date for New Guinea, possibly Earlier genetic studies tended to focus on whether contemporaneous with Australian settlement (Allen, Austronesian (Oceanic)-speaking populations could be 2003). Evidence for human habitation on the interior of distinguished from non-Austronesian (Papuan) ones, or New Britain dates to 35,000 BP (Pavlides and Gosden, whether simple geographic propinquity in this small 1994), and by 29,000 BP humans had reached Buka and region was the best discriminator. The results have been the North Solomons (Wickler and Spriggs, 1988). By conflicting, although the degree of variation is very high 20,000 years ago, archaeological evidence indicates the (e.g., Friedlaender, 1975, 1987; Merriwether et al., 1999; intentional introduction of animals into the region, as Robledo et al., 2004; Friedlaender et al., 2006). well as more extensive long-range interactions or trade As reported here, pigmentation variation in this region (e.g., Summerhayes and Allen, 1993; Allen 1996; Leave- echoes the remarkable genetic diversity observed in pre- seley and Allen, 1998). A very distinctive cultural hori- vious studies. Although the inhabitants of Island Mela- zon in the Bismarcks dates to about 3,200 years ago, nesia are generally darkly pigmented, their skin pigmen- called Lapita, after its distinctive pottery style. It was tation shows a surprising amount of diversity across the marked by a number of other novel or intrusive material region. The explanation for the pattern of diversity culture traits, including a number of domesticates (pigs, within this region cannot be tied directly to contempo- chickens, and dogs), unique shell ornament types, exten- rary UVR exposure, but rests instead on the history of sive trading networks, and new settlement patterns, ancient population migrations or other factors. focusing on certain shore locations and peripheral islands (Spriggs, 1995). It was linked to the movement of MATERIALS AND METHODS a new language into the region (Proto-Oceanic, an Aus- tronesian language). This was the ancestor of all the One thousand, one hundred and thirty-five adult indi- Austronesian languages spoken today throughout Island viduals from 12 Austronesian- and 6 Papuan-speaking Melanesia, Polynesia, and most of Micronesia. However, groups from six islands in Island Melanesia were mea- many languages that belong to a non-Austronesian stra- sured for skin and hair pigmentation by H.L.N. and tum survive, particularly in the interiors of New Guinea J.S.F. These individuals were measured on New Britain, and the larger islands of Island Melanesia. Spriggs New Ireland, and New Hanover in the Bismarck Archi- (1997) hypothesized that the Lapita culture, its exten- pelago, and nearby Bougainville. Both Austronesian sive trade networks, and the chain of Austronesian dia- (AN) and Papuan (P) language-speaking individuals lects that developed with it helped homogenize Island were included. This work was carried out as part of a Melanesia during the period 2500–2000 BC, and that larger project on the population history and settlement subsequently there was a contraction of trade networks of Island Melanesia. As such, information concerning and a local diversification of Austronesian-speaking pop- each individual’s age, village of origin, language, and the ulations in the region. As a corollary to this model, the villages and languages