What is sugested about the history of men and dogs in Chapter IV?

Sometimes as he crouched there, blinking dreamily at the flames, it seemed that the flames were of another fire, and that as he crouched by this other fire he saw another and different man from the half-breed cook before him. This other man was shorter of leg and longer of arm, with muscles that were stringy and knotty rather than rounded and swelling. The hair of this man was long and matted, and his head slanted back under it from the eyes. He uttered strange sounds, and seemed very much afraid of the darkness, into which he peered continually, clutching in his hand, which hung midway between knee and foot, a stick with a heavy stone made fast to the end. He was all but naked, a ragged and fire-scorched skin hanging part way down his back, but on his body there was much hair. In some places, across the chest and shoulders and down the outside of the arms and thighs, it was matted into almost a thick fur. He did not stand erect, but with trunk inclined forward from the hips, on legs that bent at the knees. About his body there was a peculiar springiness, or resiliency, almost catlike, and a quick alertness as of one who lived in perpetual fear of things seen and unseen.

At other times this hairy man squatted by the fire with head between his legs and slept. On such occasions his elbows were on his knees, his hands clasped above his head as though to shed rain by the hairy arms. And beyond that fire, in the circling darkness, Buck could see many gleaming coals, two by two, always two by two, which he knew to be the eyes of great beasts of prey. And he could hear the crashing of their bodies through the undergrowth, and the noises they made in the night.