The Penguin History of the World

Another important physiological change is the loss of oestrus by the female hominin. We do not know when this happened, but after it had been completed her sexual rhythm was importantly differentiated from that of other animals. Man is the only animal in which the mechanism of the oestrus (the restriction of the female’s sexual attractiveness and receptivity to the limited periods in which she is on heat) has entirely disappeared. It is easy to see the evolutionary connection between this and the prolongation of infancy: if female hominins had undergone the violent disruption of their ordinary routine which the oestrus imposes, their offspring would have been periodically exposed to a neglect which would have made their survival impossible. The selection of a genetic strain which dispensed with oestrus, therefore, was essential to the survival of the species; such a strain must have been available, though the process in which it emerged may have taken a million or a million and a half years because it cannot have been effected consciously.

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?