How to explain Polynesian Outliers’ heterogeneity?

Eighteen islands or localities, distributed across Micronesia and Melanesia, are identified as Polynesian Outliers. Their current populations display Polynesian linguistic and cultural features. Linguistics, ethnography and archaeology have questioned the modalities of their formation. Rather than foc using on long-distance voyaging and migrations of Polynesian people into the Micronesian and Melanesian regions, we synthesised archaeological and biological data, the latter frequently omitted from this type of analysis, from the regions in question. While cultural remains show sporadic evidence of external contacts, biological data display a North-South cline emphasising a decrease of Polynesian affinities from Micronesia to SouthMelanesia. We propose several hypotheses of patterns of interaction at different scales, considering various dynamics of encounters between the arriving and pre-existing populations, likely influenced by the size of the groups in contact.