In the northern Philippines, interaction between the foragers of the Peuffffablanca cave sites and the early Austronesian farmers of the Cagayan Valley (northern Luzon) was established by at least 3500 years ago. Farmers exchanged earthenware pottery, clay earrings, spindle whorls and shell beads with foragers, possibly for forest products. This exchange, however, did not, on present evidence, include cereal-based foods such as rice. The botanical evidence from the cave sites shows a heavy reliance on wild and arboreal food sources.