Neanderthal (Homo neanderthalensis), illustration. Neanderthals are our closest relatives and inhabited Europe and western Asia between around 400,000 and 40,000 years ago. They used simple tools, had mastery of fire and built shelters. It is thought that they had language and a complex social structure, living in small family groups and hunting for food. It is not known why Neanderthals became extinct, but one theory is that they were outcompeted by modern humans (Homo sapiens).