The keen eye that the human prototype inherited from his ape-like precursors was also useful to him in other ways, for food-getting, pathfinding and perceptive purposes in general. In some respects, indeed, sight may be regarded as the most serviceable of all the senses. Touch and taste, upon which the lower orders of life rely, require actual contact with the objects to be distinguished, and, consequently, only afford a concept of the immediate environment. Hearing and smell predominate among the vertebrates, have a broader range and are especially useful in this, that they allow the mind to distinguish particular sounds and odors from surrounding conditions, and so afford a perception of the local environment. The sense of sight offers still further advantages in that it conveys a concept of the special as well as of the universal environment and allows the mind not only to distinguish particular objects, but also to compare them with each other and so form a general conception of the outer world. Sight has this disadvantage, however: it only gives instantaneous information from one quarter, and necessitates a turning of the head or body to take in surrounding conditions, because light travels only along straight lines; whereas hearing and smell accord instantaneous information from all quarters, because sounds and odors disseminate in every direction from the center of disturbance. Thus though primeval man might well enough have relied upon his sense of sight exclusively for acquisitive purposes, defense demanded that he develop a sentinel sense besides. Heredity also determined this choice. Like the other anthropoids, man continued to rely upon his hearing to warn him of danger approaching from behind. Thus beside becoming adapted to walking and weapon-wielding, we may imagine the human prototype developing during the process of differentiation which fitted him for his mundane career, the keen eye and acute ear that had been handed down to him through heredity from his ape-like ancestors.
Working upon the biological principle of variability and following the interaction between heredity and environment, by a process.of reconstruction we have been able to form a tolerably complete conception of the original condition of man. He was evidently a land-dwelling, omnivorous, weapon-wielding animal. For this manner of life he was psychically and physically fitted during the process of specific differentiation. From his ape-like ancestors he inherited his prehensile hand, his keen eye and his acute ear; in adapting him to the earthly environment selection increased his cranial capacity, developed the convolutions of his brain, set him upright on his feet and accorded him the free use of his arms for acquisitive purposes. Thus endowed, primeval man was evidently enabled to cope successfully with the carnivora, and eventually make himself master of the forest.
Taking the geological location of the remains of Pithecanthropus