Running in and out among the children, sometimes pummeled by them, were a score or two of gray, four-footed, bone-awaiting creatures, who, though as yet uncounted in such relation, were destined to furnish a factor in man's advancement. They were wolves and yet no longer wolves. They had learned to cling to man, but were not yet intelligent enough or taught enough to aid him in his hunting. They were the dogs of the future, the four-footed things destined to become the closest friends of men of future ages, the descendants of the four cubs Ab and Oak had taken from the dens so many years before. It was humanizing for the children, this association of such a number together, though they ran only a little less wildly than those who had heretofore been born in the isolated caves. There came more of an average of intelligence among them, thus associated, though but little more attention was paid them than the cave men had afforded offspring in the past. There had come to Ab after Little Mok two strong sons, Reindeer and Sure-Aim, very much like him in his youth, but of them, until they reached the age of help and hunting, he saw little. Lightfoot regarded them far more closely, for, despite the many duties which had come upon her, there never disappeared the mother's tenderness and watchfulness. And so it was with Moonface, whose brood was so great, and who was like a noisy hen with chickens. So existed the hovering mother instinct with all the women of the valley, though then the mothers fished and hunted and had stirring events to distract them from domesticity and close affection almost as much as had the men. From this oddly formed community came a difference in certain ways of doing certain things, which changed man's status, which made a revolution second only to that made by the bow and for which even men of thought have not accounted as they should have done, with the illustration before them in our own times of what has followed so swiftly the use of steam and, later, of electricity. Men write of and wonder at the strange gap between what are called the Paleolithic and the Neolithic ages, that is, between the ages when the spearheads and ax and arrowheads were of stone chipped roughly into shape, and the age of stone even-edged and smoothly polished. There was really no gap worth speaking of. The Paleolithic age changed as suddenly into the Neolithic as the age of horse power changed into that of steam and electricity, allowance being always made for the slower transmission of a new intelligence in the days when men lived alone and when a hundred years in the diffusion of knowledge was as a year to-day.