The higher apes will use their fingers to turn the screws which fasten down the lid of a box in order to see what is inside. Lately the large orang in the Zoological Gardens of London succeeded, after long efforts, in unwinding the wire fastenings of its cage and escaping into the open. It climbed into a tree, and immediately constructed for itself a platform of branches which it broke off from the tree. It then sat upon this platform, as is its habit when in its native forest. Many of the larger monkeys have great skill in throwing stones, sending them with considerable force and good aim. They select stones of size and weight appropriate to their purpose, and it would not be surprising should apes have learnt to select stones for other purposes, such as cracking nuts or the shells of molluscs, in order to extract the soft nourishing food which they contain. They are known to make use of stones for such purposes, and it would be but a short step in advance for them to choose one suitable for use as a hammer, and another suitable for use as a piercing or cutting tool. And from such a stage there is a gradual and easy passage to the simplest breaking and preparation of stones for use--in fact, to the earliest fabrication of "implements."
It is obvious when we compare not only the structure but what we know of the ways and habits of the lowest savages and the highest apes, that it is not by mere strength, swiftness, or agility that man has flourished and established himself, leaving the apes far behind him as "inferior" creatures, though as a matter of fact he is not deficient in these qualities. It is by his observation, knowledge, memory, and purposive skill that he has succeeded, and it is easy to point out a whole series of modifications of form separating man from apes, which are clearly contributory to the development of the mental qualities which give him his actual superiority. I think we are justified in taking the large opposable thumb and fingers as the starting-point in man's emergence from the ape stage of his ancestry. The exploring hand, with its thumb and forefinger, is the great instrument by which the intelligence, first of the monkey and then of man, has been developed. The thumb of the gorilla is, in proportion to the size of the fingers, very much smaller than that of man, but bigger than that of the chimpanzee, and much bigger than that of the orang and of lower monkeys. It is evident that the thumb has increased in size in the man-like apes, and in man himself this increase has been carried much further, and led to the perfecting of the hand as an instrument of exploration and construction. Contributory to the perfecting of the hand has been the gradual attainment of the upright carriage, and the use of the feet alone for walking, and the reservation of the hand for delicate exploring operations, and the bringing of objects near to the eye, to the nose, the ear, and the mouth for investigation by the great organs of special sense. The foot has become "plantigrade" in connexion with the assumption of upright carriage. It has independently become plantigrade in the gibbons and the baboons. That is to say, we and they do not walk on the edge of the half-grasping foot as do the gorilla, chimpanzee, and orang, but more steadily and firmly on its flat sole (plantar surface), as do the bears and some other animals. At the same time man has lost very greatly (but not entirely) the power of grasping with his toes. The upright carriage enabled the early ancestors of man to survey, and so to judge the conditions of safety or danger at a distance from them, as well as to devote their hands to new and special uses.