Computational analysis reveals historical trajectory of East-Polynesian lunar calendars

TL;DR

This study uses computational analysis of East Polynesian lunar calendars to trace their historical development, revealing a divergence pattern that aligns with regional language splits and population movements.

Contribution

It introduces a novel computational approach to analyze and compare lunar calendar lists, linking calendar divergence with linguistic and migratory histories in East Polynesia.

Findings

Two main groups of lunar calendars identified, corresponding to linguistic subgroups.

Calendar divergence mirrors early population movements in East Polynesia.

Supports the link between cultural systems and linguistic evolution.

Abstract

We investigate a type of lunar calendar known as lists of the 'nights of the moon', found throughout East Polynesia, including Rapa Nui (Easter Island). Using computational methods, we analyzed the lexical and structural divergence of 49 calendric lists from all major archipelagos, each containing about 30 night names. Our results, presented as a rooted phylogenetic tree, show a clear split into two main groups: one including lists from Rapa Nui, Mangareva, and the Marquesas; the other comprising lists from New Zealand, Hawaii, the Cook Islands, the Austral Islands, Tahiti, and the Tuamotu. This pattern aligns with a recent alternative classification of East Polynesian languages into 'Distal' (Marquesan, Mangarevan, Rapanui) and 'Proximal' (Maori, Hawaiian, Tahitian, etc.) subgroups. Since both language and lunar calendars are symbolic systems passed down and changed within communities - and given the geographic isolation of many archipelagos - we interpret this correspondence as evidence that the early divergence of East Polynesian lunar calendars mirrors early population movements and language splits in the region.