 First contact with the populous Western Dani was made in October 1920 during the Central New Guinea Expedition, which group of explorers stayed for six months with them at their farms in the upper Swart River Valley (now "Toli Valley").The Grand Valley Dani were only sighted in the summer of 1938 from an airplane by Richard Archbold.Sweet potatoes are important in their local culture, being the most important tool used in bartering, especially in dowries.