2. Blench (2018) finds widespread Austroasiatic roots for 'river, valley', 'boat', 'fish', 'catfish sp.', 'eel', 'prawn', 'shrimp' (Central Austroasiatic), 'crab', 'tortoise', 'turtle', 'otter', 'crocodile', 'heron, fishing bird', and 'fish trap'. Archaeological evidence for the presence of agriculture in northern Indochina (northern Vietnam, Laos, and other nearby areas) dates back to only about 4,000 years B.P. (2,000 B.C.), with agriculture ultimately being introduced from further up to the north in the Yangtze valley where it has been dated to 6,000 B.P. Hence, this points to a relatively late riverine dispersal of Austroasiatic as compared to Sino-Tibetan, whose speakers had a distinct non-riverine culture.