Survival was dependent on the exploitation of seasonal variation. It is believed that Kuku Yalanji lived in the rainforest region no later than 4,000 years ago. It is known that they had high population density, and lived in semi-permanent gunyahs. Their staples for obtaining carbohydrates were the toxic seeds of Cycas media, which were leached of their poisonous compounds before cooking; two species of yam, with the variety known as bitter yam particularly sought after, supplemented by bitter walnut, candlenuts and Kuranda quandong.