Leroi-Gourhan surveyed more than sixty caves and saw order in the distribution of their images. Deer... often appeared in entranceways but were uncom… - Richard Leakey

[Fred] Spoor's observations are truly startling, In all species of the genus Homo, the inner ear structure is indistinguishable from that of modern humans. Similarly, in all species of Australopithecus, the semicircular canals look like those of apes. Does this mean that the australopithecines moved about as apes do—that is, quadrupedally? The structure of the pelvis and lower limbs speaks against this conclusion. So does a remarkable discovery my mother made in 1976: a trail of very humanlike footprints made in a layer of volcanic ash some 3.75 million years ago.

Jerison argues that we should think of brains as creating a species' version of reality. ...As brains enlarged through evolutionary time, more channels of sensory information could be handled more completely, and their input integrated more thoroughly.

If the molecular evidence is correct... almost five million years passed between the time our ancestors became bipedal and the time when they started making stone tools. Whatever the evolutionary force that produced a bipedal ape, it was not linked with the ability to make and use tools. However, many anthropologists believe that the advent of technology 2.5 million years ago did coincide with the beginnings of brain expansion.