Adaptation to new environments is an important issue in colonization research with implications for accurately establishing the timing of human arrival and interpreting the dispersal pattern from the distribution of early archaeological sites. Island groups frequently contain a diverse range of landscapes and geographic variation in their colonization records that might reflect the environmental preference of prehistoric migrants. In the Palau Islands the large island of Babeldaob may have been colonized by 4300 cal BP on palaeoenvironmental evidence, while the oldest archaeological deposits in the small limestone islands of southern Palau date to ∼ca. 3000 cal BP. Does the discrepancy in colonization ages represent a predilection for the large volcanic island relative to small limestone islands? To examine the timing of human arrival in southern Palau an early site on Ulong Island was re-excavated, along with ancillary investigations to calculate a local reservoir value (ΔR) to apply to new marine shell ¹⁴C ages and investigation of a buried sea-notch to estimate the impact of sea-level change and tectonic movement. Human arrival in southern Palau is dated to no earlier than 3100-2900 cal BP. Neolithic dispersal in other island environments in the Pacific is reviewed to see whether colonization of large islands tended to precede use of small islands. The general pattern is for the oldest sites to be located on large islands, with human activity archaeologically visible throughout an archipelago within 100-300 years. A similar interval applied to Palau would put colonization at 3400-3100 cal BP, but this needs to be confirmed by palaeoenvironmental and archaeological investigations in coastal Babeldaob.