VIII. Man's First Ancestors

We must bear in mind that the field of sensation possessed by these human forefathers was of a general character and as yet quite vague and indefinite. So far, only two of the kinds of sensation we now possess were differentiated: the sense of hearing and that of touch. By reason of the changes, however, which the body was undergoing, as well as its physical environment, the whole human form was no longer capable of acting, so to speak, as “all ear.” Henceforward a specialised part of the body retained the power of responding to the delicate vibrations, and supplied the material from which was gradually developed the organ of hearing we now possess, whilst the rest of the body remained almost entirely an organ of touch.