Stone tools from Dzudzuana Cave contain traces of indigotin, a brilliant blue compound that forms the basis of indigo dye. But this has left the archaeologists with an even larger question; what were these ancient humans doing grinding up bitter, inedible leaves to create this blue dye? This process requires deliberate mechanical action, and the mere presence of indigotin proves these early humans were actively processing it. So what were these ancient humans using it for? The sophisticated plant processing evidenced at Dzudzuana suggests these early humans possessed detailed ecological knowledge.