Biology cannot be ignored when we examine the full sweep of hominid evolution over the past 2.5 million years. Our earliest tool-making ancestors of 2 million years ago were very different from us in stature, in manual dexterity, and in brain volume. Indeed, marked differences persisted until relatively recent times. Even a cursory examination of a 100,000-year-old Neandertal skeleton alongside that of a modern human provides a striking contrast (Fig. 2,3). Given such clear physical differences, when we compare the material patterns left behind by our much more distant ancestors, we must consider the possibility that they did not share all of our capabilities. A few chipped stones at Olduvai Gorge in levels dated to nearly 2 million years ago cannot be taken to imply culture as it is exhibited by modern humans and as it was defined by Edward Burnett Tylor:
...that complex whole which includes knowledge, belief, art, morals, custom and any other capabilities and habits acquired by man as a member of society.