Ancient Solomon Islands mtDNA: assessing Holocene settlement and the impact of European contact

In this paper we present a case study to test the effect of 19th-20th century colonial impact on the mitochondrial DNA diversity of Solomon Islanders and to investigate the complex stratigraphy of settlement in this archipelago during and after the Lapita period. We extracted DNA from hairs and teeth belonging to 21 individuals collected by the Somerville expedition during the late 19th-century, and typed them for mitochondrial DNA (mtDNA) hypervariable region I (HVS-I) and the intergenic COII/tRNALys 9-base pair deletion (9 bp-del). Comparison of these genetic data with those available from the modern Solomon Islanders and Southeast Asian and Oceanic populations conflicts with the hypothesis of drastic changes in Solomon maternal genepool diversity, indicating that the last century putative bottleneck is not detectable through our genetic data. In addition, the ancient and modern Solomon haplogroup distribution (e.g. M27 haplogroup) suggests, in agreement with some archaeological and linguistic models, that Early Lapita populations expanding out of the Bismarck Archipelago had little or no contact with indigenous non-Austronesian populations in Bougainville and the Solomon Islands. This finding indicates smaller scale analyses reveal a more complex reality of genetic admixture in some parts of Oceania than is often assumed in current debates.