(3) The erect attitude was reached by the apes in the course of adaptation to arboreal life;[4] but the erect gait as the normal mode of progression is (if we neglect the gibbons’ imperfect performance) peculiar to ourselves; and such a gait was attained because the most successful hunters followed their prey afoot upon the ground. The feeble ineffective shuffle of the anthropoids upon the ground, supporting themselves with their arms where there are no overhanging boughs to swing by and help themselves along, could not have served the hunter, especially if he was to leave the forest. We may, indeed, suppose that at first prey was sometimes attacked by leaping upon it from the branch of a tree, as leopards sometimes do; but the less our ancestor in his new career trusted to trees the better for him. Such simple strategy could not make him a dominant animal throughout the world; nothing could do this but the gradual attainment of erect gait adapted to running down his prey. Hence the numerous modifications of structure necessary to it, whenever from time to time they occurred, were preserved and accumulated by natural selection: namely, the curving of the vertebral column, the balancing of the head upon a relatively slender neck, changes in the joints, bones and muscles of the legs, the lengthening of the leg and the specialisation of the foot (in which the heel is developed more than in the gorilla, and the great toe is lengthened and lies parallel with the other toes). (4) The specialisation of the legs and feet, as it proceeded, made possible the specialisation of the hands: being gradually rid of the task of assisting locomotion, whether in trees or on the ground, they were used in grappling with prey, seconded by massive jaws and powerful canine teeth. In course of time they brought cudgels and stones to the encounter, and after many ages began to alter such means of offence into weapons that might be called artefacts. These simple beginnings probably occupied an immense time, perhaps more than half of the total period down to the present. The utility and consequent selection of hands had been great throughout; but their final development may be referred to the making and using of weapons fashioned according to a mental pattern. Those who had the best hands were selected because they made the best weapons and used them best; but we know from remains of several palæolithic stages of the art of manufacturing implements how very slowly the art improved.