Using seafaring simulations and shortest-hop trajectories to model the prehistoric colonization of Remote Oceania

Abstract

The prehistoric colonization of islands in Remote Oceania that began ∼3400 B.P. represents what was arguably the most expansive and ambitious maritime dispersal of humans across any of the world's seas or oceans. Though archaeological evidence has provided a relatively clear picture of when many of the major island groups were colonized, there is still considerable debate as to where these settlers originated from and their strategies/trajectories used to reach habitable land that other datasets (genetic, linguistic) are also still trying to resolve. To address these issues, we have harnessed the power of high-resolution climatic and oceanographic datasets in multiple seafaring simulation platforms to examine major pulses of colonization in the region. Our analysis, which takes into consideration currents, land distribution, wind periodicity, the influence of El Niño Southern Oscillation (ENSO) events, and "shortest-hop" trajectories, demonstrate that (i) seasonal and semiannual climatic changes were highly influential in structuring ancient Pacific voyaging; (ii) western Micronesia was likely settled from somewhere around the Maluku (Molucca) Islands; (iii) Samoa was the most probable staging area for the colonization of East Polynesia; and (iv) although there are major differences in success rates depending on time of year and the occurrence of ENSO events, settlement of Hawai'i and New Zealand is possible from the Marquesas or Society Islands, the same being the case for settlement of Easter Island from Mangareva or the Marquesas.

Keywords: ENSO; Lapita expansion; Pacific colonization; ancient seafaring; computer simulations.

Fig. S1.

Paths of successful crossings for directed voyaging simulations between (Upper) Samoa and the Marquesas and (Lower) Samoa and the Society Islands. Both results refer to trips started under April conditions.

Fig. S2.

Paths of successful crossings for directed voyaging simulations between (Top) Society Islands and Easter Island with start under February conditions; (Center) Marquesas and Easter Island for start under August conditions; and (Bottom) Mangareva and Easter Island for start under January conditions.

Fig. 1.

All shortest-hop paths and mean westerly wind conditions. (Upper) Filled red lines: all shortest-hop paths with starts from central and southern Philippines, Maluku, and Solomon departure areas; dashed red line: present-day sea level and all island sizes directed shortest-hop path from New Guinea to Marianas. Gray shade areas with westerly winds on the green line: annual average; dashed yellow line: all years June–November average; blue dashed line: El Niño June–November average. See Table S6 for island abbreviations. (Lower) Same as Upper with gray shade showing areas with westerly winds on the dashed yellow line, all years December–February average; blue dashed line: El Niño December–February average.

Fig. 2.

Crossing distance and along-path spell displacement and frequency. (Top) Shortest-hop path from Maluku (Mal) with present-day sea level and all islands considered. (Center) Eastward distance for individual crossings above 50 km (red X’s at the longitude of the arrival island) and average potential eastward displacement of vessels sailing downwind with 50% efficiency for westerly spells lasting 3, 5, and 7 d (filled lines). (Bottom) Average annual frequency of 3-, 5-, and 7-d westerly spells (same color scheme as Center). Potential displacement and frequency represent along-path averages.

Fig. 3.

ENSO annual anomalies. Wind (green vectors) and precipitation (colors, mm/d) deviations from the long-term annual mean during El Niño (Upper) and La Niña (Lower) years.

Fig. S3.

Same as Fig. 3 but for northern crossings starting from the Solomons (Sol). (Top) Shortest-hop path with present-day sea level and all islands considered. (Center) Eastward distance for individual crossings above 50 km (red X’s at the longitude of the arrival island) and average potential eastward displacement of vessels sailing downwind with 50% efficiency for spells lasting 3, 5, and 7 d (filled lines). (Bottom) Average annual frequency of 3-, 5-, and 7-d spells (same color scheme as the center). Potential displacement and frequency represent along-path averages.

Fig. S4.

Average duration of eastward spells in days during (Upper Left) all SH summers (December–February); (Lower Left) El Niño SH summers; (Upper Right) all NH autumns (September–November); and (Lower Right) El Niño NH autumns. Note the difference in color scale between Left and Right. In all panels, red lines represent shortest-hop trajectories (Fig. 1).

Fig. S5.

ENSO seasonal anomalies. Wind (green vectors) and precipitation (colors, mm/d) deviations from the long-term December–January–February mean under El Niño (Upper) and La Niña (Lower) conditions.

Fig. S6.

ENSO seasonal anomalies. Wind (green vectors) and precipitation (colors, mm/day). (Upper) deviations from the long-term June–July–August mean under El Niño conditions. (Lower) Deviations from the long-term September–October–November mean under La Niña conditions.

Fig. 4.

Synthesis of results. Filled and dashed arrows refer to crossings that, according to simulations, are viable under downwind and directed sailing, respectively. Numbered notes provide additional information for particular voyages. Seasons (e.g., NH summer) refer to period of the year when environmental conditions facilitate crossing. Colors refer to aspects of ENSO-related anomalies that favor particular crossings (e.g., dark green is used for crossings where, under El Niño conditions, departure areas are drier and wind anomalies help displacement toward target). The open arrow (4) reflects the fact that this is a general trend and not a particular crossing. Arrows from Society Islands and Marquesas that point out of the map (7) refer to crossings toward Easter Island, which is not shown.