Southeast Asian stone-age sites fall roughly into two groups: (1) coastal, espe- cially estuarine, sites whose inhabitants exploited the bountiful resources of the sea as well as the coastal lowlands; and (2) inland sites situated in caves and rock shelters above river valleys. Many early coastal sites must have been progressively submerged as sea levels rose after the last ice age, around 20,000 years ago, forcing people to move to higher ground. Inland sites reveal that, though population was more thinly spread than along the coast, most of the interior of mainland Southeast Asia, including the area covered by present-day Laos, was already widely inhabited by these early hunter-gatherers. Who they were we do not know, though they may have been akin to the Orang Asli of peninsular Malaya or the negritos of the Andaman Islands.