People of the sea, or of the soil? How the balance of marine and terrestrial resource availability informs maximum population on four Polynesian islands

Abstract

Most studies of the food resource potential of early Polynesian populations focus exclusively on agricultural potential, and specifically starchy staples, despite the importance of the marine world to the Polynesians. In an attempt to more accurately estimate total precontact food resource availability, we characterized the terrestrial and near-shore marine environments of four Polynesian islands: Moʻorea, Maupiti, Mangareva and Taravai. We estimate the agricultural potential of each island after a consideration of the ecological factors related to productivity. We also estimate the productivity of the near-shore marine environment as a function of surface area. Using a range of fish yield scenarios from Pacific subsistence systems we scale relative measures of faunal food biomass derived from local archaeological excavations to generate absolute biomass estimates. We convert our estimates of agricultural and fished/foraged food potential into a maximum population size based on calorie availability. Moʻorea’s fertile valleys and wetlands would potentially generate sufficient food energy, mostly from starchy staples, to support a considerable population, many times larger than the other islands. In the most likely fish yield scenario Moʻorea gets only 0.4% of its calories from marine sources, while the others range from 7-18%. These relative inputs reflect the vast superiority in productivity (in terms of calories per km²) of agricultural vs near-shore marine zones. We also find that population size on islands with smaller fringing reefs, as illustrated by Moʻorea, may have been limited by a lack of fish protein. Moʻorea’s maximum population is approximately halved when diet breadth is considered.