Abstract
The pattern of prehistoric human dispersal through Eastern Polynesia, representing one of the last major migrations in human history, remains highly contested with conflicting archaeological evidence. The commensal approach, using the phylogenies of commensal animal and plant species has been increasingly applied since the late 1990s as a proxy for human movement. Previous genetic commensal research using the Pacific rat, Rattus exulans, a species transported across Remote Oceania as part of the Polynesian expansion, has been largely unsuccessful in distinguishing finer-scale movements between Remote Oceanic islands, with the majority of rat samples adhering to the same mitochondrial control region haplotype. It was anticipated that with greater molecular resolution provided by complete mitochondrial genome sequencing, a greater number of Pacific rat lineages would be distinguished and could be used as a proxy to investigate the origins and dispersals of Eastern Polynesian people.
Archaeological rat specimens were obtained from the earliest occupational contexts across Western and Eastern Polynesia. Complete mitochondrial sequencing of both ancient and modern specimens of the Pacific rat was undertaken. Nine ancient and twenty-five modern haplotype lineages were identified. A central haplotype, derived from an ancestral haplotype in Western Polynesia, is ancestral to all Eastern Polynesian rat populations and reflects a previously proposed central East Polynesian homeland region from which eastern expansion occurred. An Easter Island and Tubuai (Austral Islands) grouping of related haplotypes suggests that both islands were established by the same colonisation wave, proposed to have originated in the central homeland region before dispersing through the south-eastern corridor of Eastern Polynesia. The application of second-generation sequencing in generating complete and credible mitochondrial genomes from archaeological and modern commensal specimens provides greater molecular resolution to investigate prehistoric dispersal and interaction spheres across the Pacific.