The use of strontium isotopes as an indicator of migration in human and pig Lapita populations in the Bismarck Archipelago, Papua New Guinea Ben J. Shaw a, * , Glenn R. Summerhayes b , Hallie R. Buckley a , Joel A. Baker c a University of Otago, Department of Anatomy and Structural Biology, PO Box 913, Dunedin, New Zealand b Department of Anthropology, Gender and Sociology, University of Otago, PO Box 56, Dunedin, New Zealand c School of Geography, Environment and Earth Sciences, Victoria University, PO Box 600, Wellington New Zealand article info Article history: Received 15 September 2008 Received in revised form 23 October 2008 Accepted 10 December 2008 Keywords: Lapita cultural complex Migration Anir islands Bismarck Archipelago Strontium isotopes Pigs (Sus scrofa) abstract This paper examines the potential use of strontium isotopes ( 87 Sr/ 86 Sr) for identifying migration within Lapita populations and their commensal animals, specifically the pig (Sus scrofa). Lapita people (ca. 3300–2200 BP) were the initial colonists of the island groups to the east of the Solomon Islands, spreading from Papua New Guinea to Tonga and Samoa within a few centuries. Mobility is assumed to have been an important mechanism for maintaining cultural solidarity between Lapita communities. It has been previously argued that Lapita populations became progressively more sedentary over time after the initial colonising events. Two Lapita sites, Kamgot and Balbalankin, from the Anir Islands in the Bismarck Archipelago are included in the analysis and fall within the Early (ca. 3300–3000/2900 BP) and Middle (ca. 3000/2900–2700 BP) Lapita periods respectively. Ten tooth enamel samples from Lapita human and pig teeth as well as modern teeth were analysed for strontium isotopes. The mean values for the individuals from both sites were higher than the geological value obtained for the Anir Islands reflecting the incorporation of marine-derived strontium into their tooth enamel taken up in their diet. Although the sample sites have similar environments there was a difference between the local ranges of the strontium isotopic data. One Lapita age pig and one potentially modern pig from Kamgot fell well outside the local distribution for the site and were considered to be non-local. The extreme distribution of the two outliers suggests they came from two geographically separate locations. The results from the Anir Islands when compared with strontium results from other prehistoric Pacific Island populations suggest there is sufficient variation between island groups in terms of the biologically available strontium to justify further research. The present results are discussed in terms of using pigs as a proxy for human mobility as well as an indicator for the ‘local’ range of an archaeological population by treating human and pigs as separate populations. Strontium isotopes therefore provide the opportunity to investigate migration in Lapita populations on a finer scale than was previously possible. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction The use of strontium isotopes ( 87 Sr/ 86 Sr) has frequently been used in archaeological research to determine migration in prehis- toric populations. This technique, when applied to tooth enamel, is based on the premise that while teeth are developing during childhood the enamel takes on the geological strontium isotope signature, primarily through the ingestion of foods grown in the local area (Bentley, 2006). Therefore, an adult’s permanent denti- tion will hold the geological signature of where the individual spent their childhood. If this differs from the rest of the population it is likely the individual migrated during their adult years to the place of their death. This paper explores whether there is enough vari- ation in the biologically available strontium to identify migrants in archaeological assemblages within the Bismarck Archipelago in the Southwest Pacific Islands and importantly, to begin to determine their geographic origins. 1.1. Pacific island colonisation Humans have occupied Near Oceania for at least 40,000 years, with occupation sites found in mainland New Guinea, and the islands comprising the Bismarck Archipelago (Summerhayes, 2007b). At 3300 BP, archaeological evidence of a new people called Lapita is found in the Bismarck Archipelago in the form of new coastal/beach settlements, the introduction of pottery and the introduction of Southeast Asian domesticates such as the dog, pig * Corresponding author. E-mail address: ben.shaw@anatomy.otago.ac.nz (B.J. Shaw). Contents lists available at ScienceDirect Journal of Archaeological Science journal homepage: http://www.elsevier.com/locate/jas 0305-4403/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2008.12.010 Journal of Archaeological Science 36 (2009) 1079–1091