The original inhabitants of the Plain of Jars were Austro-Asiatic peoples, who lived by hunting and gathering before the advent of agriculture. Skilled at river navigation using canoes, traders used routes through the mountains, especially waterways, from earliest times. The most important river route was the Mekong because of its many tributaries, the chief northern tributary being the Nam (River) Ngum which originates in the hills north of the Plain. These water routes allowed traders to penetrate deep into the hinterland, where they bought products such as cardamom, gum, and many foods.