Such a change has radical implications. The increasing attractiveness and receptivity of females to males make individual choice much more significant in mating. The selection of a partner is less shaped by the rhythm of nature; we are at the start of a very long and obscure road which leads to the idea of sexual love. Together with prolonged infant dependency, the new possibilities of individual selection point ahead also to the stable and enduring family unit of father, mother and offspring, an institution unique to mankind. Some have even speculated that incest taboos (which are in practice well-nigh universal, however much the precise identification of the prohibited relationships may vary) originate in the recognition of the dangers presented by socially immature but sexually adult young males for long periods in close association with females who are always potentially sexually receptive.
In such matters it is best to be cautious. The evidence can take us only a very little way. Moreover, it is drawn from a very long span of time, a huge period which would have given time for considerable physical, psychological and technological evolution. The earliest forms of Homo erectus may not have been much like the last, some of whom have been classified by some scientists as archaic forms of the next evolutionary stage of the hominin line. Yet all reflections support the general hypothesis that the changes in hominins observable while Homo erectus occupies the centre of our stage were especially important in defining the arcs within which humanity was to evolve. He had unprecedented capacity to manipulate his environment, feeble though his handhold on it may seem to us. Besides the hand-axes which make possible the observation of his cultural traditions, late forms of Homo erectus left behind the earliest surviving traces of constructed dwellings (huts, sometimes fifty feet long, built of branches, with stone-slab or skin floors), the earliest worked wood, the first wooden spear and the earliest container, a wooden bowl. Creation on such a scale hints strongly at a new level of mental ability, at a conception of the object formed before manufacture is begun, and perhaps an idea of process. Some have argued far more. In the repetition of simple forms, triangles, ellipses and ovals, in huge numbers of examples of stone tools, there has been discerned intense care to produce regular shapes which does not seem proportionate to any small gain in efficiency which may have been achieved. Can there be discerned in this the first tiny budding of the aesthetic sense?
The greatest of prehistoric technical and cultural advances was made when some of these creatures learnt how to manage fire. Until recently, the earliest available evidence of its use came from China, and probably from between 300,000 and 500,000 years ago. But very recent discoveries in the Transvaal have provided evidence, convincing to some scholars, that hominins there were using fire well before that. It remains fairly certain that Homo erectus never learnt how to make fire and that even his successors did not for a long time possess this skill. That he knew how to use it, on the other hand, is indisputable. The importance of this knowledge is attested by the folklore of many later peoples; in almost all of them a heroic figure or magical beast first seizes fire. A violation of the supernatural order is implied: in the Greek legend Prometheus steals the fire of the gods. This is suggestive, not solid, but perhaps the first fire was taken from outbreaks of natural gas or volcanic activity. Culturally, economically, socially and technologically, fire was a revolutionary instrument – if we again remember that a prehistoric ‘revolution’ took millennia. It brought the possibility of warmth and light and therefore of a double extension of the habitable environment, into the cold and into the dark. In physical terms, one obvious expression of this was the occupation of caves. Animals could now be driven out and kept out by fire (and perhaps the seed lies here of the use of fire to drive big game in hunting). Technology could move forward: spears could be hardened in fires and cooking became possible, indigestible substances such as seeds becoming sources of food and distasteful or bitter plants edible. This must have stimulated attention to the variety and availability of plant life; the science of botany was stirring without anyone knowing it.
Fire must have influenced mentality more directly, too. It was another factor strengthening the tendency to conscious inhibition and restraint, and therefore their evolutionary importance. The focus of the cooking fire as the source of light and warmth had also the deep psychological power which it still retains. Around the hearths after dark gathered a community almost certainly already aware of itself as a small and meaningful unit against a chaotic and unfriendly background. Language – of whose origins we as yet know nothing – would have been sharpened by a new kind of group intercourse. The group itself would be elaborated, too, in its structure. At some point, fire-bearers and fire specialists appeared, beings of awesome and mysterious importance, for on them depended life and death. They carried and guarded the great liberating tool, and the need to guard it must sometimes have made them masters. Yet the deepest tendency of this new power always ran towards the liberation of mankind. Fire began to break up the iron rigidity of night and day and even the discipline of the seasons. It thus carried further the breakdown of the great objective natural rhythms which bound our fireless ancestors. Behaviour could be less routine and automatic. There is even a discernible possibility of leisure.
Big-game hunting was the other great achievement of Homo erectus. Its origins must lie far back in the scavenging which turned vegetarian hominids into omnivores. Meat-eating provided concentrated protein. It released meat-eaters from the incessant nibbling of so many vegetarian creatures, and so permitted economies of effort. It is one of the first signs that the capacity for conscious restraint is at work when food is being carried home to be shared tomorrow rather than consumed on the spot today. At the beginning of the archaeological record, an elephant and perhaps a few giraffes and buffaloes were among the beasts whose scavenged meat was consumed at Olduvai, but for a long time the bones of smaller animals vastly preponderate in the rubbish. By about 300,000 years ago the picture is wholly altered.
This may be where we can find a clue to the way by which Australopithecus and his relatives were replaced by the bigger, more efficient Homo erectus. A new food supply permits larger consumption but also imposes new environments: game has to be followed if meat-eating becomes general. As the hominins become more or less parasitic upon other species there follows further exploration of territory and new settlements, too, as sites particularly favoured by the mammoth or woolly rhinoceros are identified. Knowledge of such facts has to be learnt and passed on; technique has to be transmitted and guarded, for the skills required to trap, kill and dismember the huge beasts of antiquity were enormous in relation to anything which preceded them. What is more, they were co-operative skills: only large numbers could carry out so complex an operation as the driving – perhaps by fire – of game to a killing-ground favourable because of bogs in which a weighty creature would flounder, or because of a precipice, well-placed vantage points, or secure platforms for the hunters. Few weapons were available to supplement natural traps and, once dead, the victims presented further problems. With only wood, stone and flint, they had to be cut up and removed to the home base. Once carried home, the new supplies of meat mark another step towards the provision of leisure as the consumer is released for a time from the drudgery of ceaselessly rummaging in his environment for small, but continuously available, quantities of nourishment.