Human occupation of New Guinea had begun 50,000 years ago, but islands further east were settled only in Recent times. In part of the New Guinea highlands, wet and dry horticultural systems began by 9000 years ago. Local intensification is evident until the present, but only the most recent major crop (sweet potato, which has been grown in the region for less than 300 years) is documented. On the south coast, exchange systems and economies locally diversify over the last two millennia. In the Melanesian islands, exotic materials were moved 3000 kilometers 3000 years ago, but whether traders or colonists were involved is not yet clear. The prehistory of the area is proving more complex than was believed even a decade ago.