In spite of all this vigorous policing, malingerers and deserters turned aside from the upward line of march at every unguarded point or fork in the road, escaped from the struggle, and settled down in ease and stagnation or degeneration, like our very distant cousins, the monkeys and lower apes. Long-continued progress is a marked exception, not the rule, in the animal world, and is maintained only by the "saving remnant." And these continue to progress mainly because Nature is "always a-chivying of them and a-telling them to move on," as Poor Joe said of Detective Bucket, and her guiding wand is the spur of necessity. The Primates, or apes, are, as we have seen, the highest order of the great class of mammals. Most of them, like other comparatively defenseless vertebrates, are gregarious or even social.[3] They have a feeling of kind, if not of kindness, toward one another. This sociability, together with the family as a unit of social structure, has contributed incalculably to human intellectual and moral development. Man is a Primate, a distant cousin of the highest apes, though no one of these represents our "furry arboreal ancestor with pointed ears." Arboreal life was an excellent preparatory training toward human development. Our primate ancestor was probably of fair size. In climbing he set his feet on one branch and grasped with his hands the branch above his head. Foot and leg were used to support the body, hand and arm for pulling. Thus the hand became a true hand and the foot a genuine foot, opening up the possibility of the erect posture on the ground and the adaptation of the hand to higher uses. Meanwhile the climbing and leaping from branch to branch, the measuring with the eye of distances and strength of branches, the power of grasping the right point at the right instant, and all the complicated series of movements combined in this form of locomotion furnished a marvellous set of exercises not only for the muscles but for the higher centres in the cortex of the brain. Very probably gregarious life and rude play, so common among apes, was an extension course along somewhat similar lines. Our ancestors became at home in and well adapted to arboreal life, but the adaptation was never extreme. It was rather what Jones[4] has called a "successful minimal adaptation." They used arboreal life without abusing it by over-adaptation, which would have enslaved them, and made life on the ground an impossibility when the time came for their promotion to this new and more advanced stage.