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Computational analysis reveals historical trajectory of East-Polynesian lunar calendars

Miguel Valério, Fabio Tamburini, Michele Corazza

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.

Computational analysis reveals historical trajectory of East-Polynesian lunar calendars

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.

Paper Structure

This paper contains 13 sections, 13 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction: The 'nights of the moon' in East Polynesia
  2. Materials and Methods
  3. Results and Discussion
  4. Conclusions

Figures (4)

  • Figure 1: The 'triangle’ of East-Polynesian islands and the Samoan-Tongan area (West Polynesia). Created using the Free and Open Source QGIS.
  • Figure 2: Definition of the Edit Distance: $wD$, $wI$, and $wS$ represent the weight penalties for sign deletion, insertion, and substitution, respectively. In this study, $wD=wI=1$ and $wS=2$.
  • Figure 3: Phylogeny of 49 lists of ’the nights of the moon’ from East Polynesia: unrooted (A) and rooted using the MAD algorithm (B). Key to the macro-provenances (islands or archipelagos) of the calendric lists: AUSTR: Austral Islands; HAW: Hawai'i; MAO: Aotearoa/New Zealand; MGV: Mangareva (in the Gambier archipelago) MRQ: Marquesas Islands; MORI: Moriori/Chatham Islands; NCOOK: Northern Cook Islands; SCOOK: Southern Cook Islands; RPN: Rapa Nui/Easter Island; TAH: Tahiti and neighboring islands (Society Islands, French Polynesia); TUA: Tuamotu Islands. See S1A Appendix for the specific source of each list.
  • Figure 4: Wilson's alternative subgrouping of East-Polynesian languages into Proto-East Polynesian ‘Proximal’ and ‘Distal’ divisions (adapted from wilson2021EPsub).