which followed if we are to gain an objective understanding of the present-day behaviour of the species.
Faced with a new environment, our ancestors encountered a bleak prospect. They had to become either better killers than the old-time carnivores, or better grazers than the old-time herbivores. We know today that, in a sense, success has been won on both scores; but agriculture is only a few thousand years old, and we are dealing in millions of years. Specialised exploitation of the plant life of the open country was beyond the capacity of our early ancestors and had to await the development of advanced techniques of modern times. The digestive system necessary for a direct conquest of the grassland food supply was lacking. The fruit and nut diet of the forest could be adapted to a root and bulb diet at ground level, but the limitations were severe. Instead of lazily reaching out to the end of the branch for a luscious ripe fruit, the vegetable-seeking ground ape would be forced to scratch and scrapa painstakingly in the hard earth for his precious food.
His old forest diet, however, was not all fruit and nut. Animal proteins were undoubtedly of great importance to him. He came originally, after all, from basic insectivore stock, and his ancient arboreal home had always been rich in insect life. Juicy bugs, eggs, young helpless nestlings, tree-frogs and small reptiles were all grist to his mill. What is more, they posed no great problems for his rather generalise digestive system. Down on the ground this source of food supply was by no means absent and there was nothing to stop him increasing this part of his diet. At first, he was no match for the professional killer of the carnivore world. Even a small mongoose, not to mention a big cat, could beat him to the kill. But young animals of all kinds, helpless ones or sick ones, were there for the taking, and the first step on the road to major meat-eating was an easy one. The really big prizes, however, were poised on long, stilt-like legs, ready to flee at a moment’s notice at quite impossible speeds. The protein-laden ungulates were beyond his grasp.
This brings us to the last million or so years of the naked ape’s ancestral history, and to a series of shattering and increasingly dramatic developments. Several things happened together, and it is important to realise this. All too often, when the story is told, the separate parts of it are spread out as if one major advance led to another, but this is misleading. The ancestral ground-apes already had large and high-quality brains. They had good eyes and efficient grasping hands. They inevitably, as primates, had some degree of social organisation. With strong pressure on them to increase their prey-killing prowess, vital changes began to take place. They became more upright—fast, better runners. Their hands became freed from locomotion duties—strong, efficient weapon-holders. Their brains became more complex—brighter, quicker decision-makers. These things did not follow one another in a major, set sequence; they blossomed together, minute advances being made first in one quality and then in another, each urging the other on. A hunting ape, a killer ape, was in the making.
It could be argued that evolution might have favoured the less drastic step of developing a more typical cat or do like killer, a kind of cat-ape or dog-ape, by the simple process of enlarging the teeth and nails into savage fang-like and claw-like weapons. But this would have put the ancestral ground-ape into direct competition with the already highly specialised cat and dog killers. It would have meant competing with them on their own terms, and the outcome would no doubt have been disastrous for the primates in question. (For all we know, this may actually have been tried and failed so badly that the evidence has not been found.) Instead, an entirely new approach was made, using artificial weapons instead of natural ones, and it