Coastal and marine adaptation during the Pleistocene and Holocene in Island Southeast Asia

Abstract

The role of coastal and marine environments in early human subsistence and migration remains a subject of ongoing debate in archaeology. Traditional models suggest that systematic marine resource use emerged only in the Mid- to Late Holocene, primarily in response to increased pressure on terrestrial ecosystems. In contrast, revisionist views argue for much earlier coastal engagement, potentially as far back as 160,000 years ago. Island Southeast Asia (ISEA), a crucial maritime corridor toward Sahul and the western Pacific, presents a complex archaeological record. Although many pre-Last Glacial Maximum (LGM) coastal sites were likely submerged by post-glacial sea-level rise, ISEA retains a comparatively rich collection of pre-LGM coastal localities compared to other regions, highlighting flexible, context-specific subsistence strategies with terrestrial resources consistently central to early diets. Wallacea offers a notable exception within ISEA due to its tectonic complexity and steep coastlines, which have preserved many coastal zones. In the Lesser Sunda Islands, archaeological evidence demonstrates a deep-time continuity of coastal subsistence from at least 50-40 ka into the Holocene. Limited terrestrial fauna combined with abundant marine resources fostered long-term reliance on coastal foraging and fishing. This trajectory can be divided into four phases: (1) early occupation (50-23 ka), with sporadic coastal use; (2) post-LGM adaptation (22-16 ka), featuring increased marine exploitation and maritime technologies; (3) intensified use during rapid sea-level rise (15-8 ka) linked to demographic expansion; and (4) Mid- to Late Holocene occupation (7 ka-present), characterized by stable coastlines supporting permanent settlements and agricultural transition. Together, the evidence supports a middle-ground model where coastal resource use intensified after the LGM alongside rising sea levels and habitat changes. The four-phase framework from the Lesser Sundas illustrates a progression from opportunistic marine exploitation to specialized fishing and permanent settlement, shaped by ecological constraints and opportunities. This nuanced record also informs broader human migration patterns, indicating that crossings from Sunda to Sahul- and perhaps earlier Out of Africa dispersals - relied on a flexible balance of coastal and terrestrial resources. While intertidal foraging aided mobility, high-calorie terrestrial hunting remained crucial for demographic growth. Wallacean data suggest migration routes followed ecologically favorable zones, serving as stepping stones for dispersal. In sum, evidence from ISEA challenges strict distinctions between coastal and terrestrial subsistence. Instead, it reveals adaptive, mixed strategies shaped by local ecology, technology, and environmental dynamics - flexible approaches that were central to early human survival and expansion across this archipelagic landscape. Show more