The key role of the upper and middle Mekong in the expansion of settled ag- riculture from Yunnan to the plains of northern and northeastern Thailand has been indicated by a site survey of the upper reaches of the river and its northern tributaries. This revealed numerous small settlement mounds, along with samples of the black incised pottery common to Yunnan and Vietnam (Higham 2002). None of these sites in Laos have yet been scientifically excavated, but what the pattern of settlement sug- gests is the intrusion of a new population, in all likelihood speakers of Austroasiatic (Mon-Khmer) languages, which by the last centuries BCE had spread south across the plains of the central Chao Phraya and down the Mekong into Cambodia. They were accompanied by the domestic dog, the first remains of which date from early agricultural sites. At the same time, Austronesian speakers (of the Chamic subgroup) had settled along the coast of Vietnam, perhaps around the lower Mekong Delta area later identified with the kingdom of Funan.