However it may have occurred, this new brain growth added another dimension to the primate brain’s neocortex – the unique human integrative and analytical function which I call the postconscious. This was a growth of intelligence, a further extension of the apefolk mental system, but not just another appended mass of cells to give new dimensions to instinct, as the preconscious and conscious faculties had been. This was an added level, a complete mind in its own right, able critically to observe the motivation and behaviour of the self with which it was associated, and to judge that self with integrity. This level was the superior of instinct, capable of taking full responsibility for the self. In order to do so, instead of merely observing that which was of direct instinctive interest, and a little beyond out of curiosity, it had to observe everything possible, firstly because there was no telling what foreknowledge the humans would require to succeed in these their new extra-instinctive activities, and secondly because everything is grist to the mill of total understanding, and it would be only by total understanding that the postconscious could ascertain what was best for the human species.
It seems to me that ten thousand million new neurones were created, or a new genetic programme was set up allowing and preparing for their creation or activation and interconnection as, or if and when, required (making the whole cortex up to one hundred thousand million actual or possible neurones, and a possible number of interconnections now estimated at ten to the power of several millions) to give this enormous extra observing, reasoning and memorising capacity. While the postconscious was fully aware of everything going on in the conscious, its own workings were screened off from the latter, unconscious, and only its conclusions offered to the conscious self. This faculty must have developed remarkably quickly, because it would not be reliably effective until it became a complete system and there was an urgent and vital need for it. In the first human child it must have appeared as a tumour, growing to such an extent that the brain pressed downwards within the fixed-dimension skull to the point where it compressed the throat and windpipe. Whereas it is assumed that the apefolk were able to breath and swallow at the same time, as monkeys can, the first human could now only do these things alternately, and this led to the formation of the larynx which enabled us to articulate speech. This transformation evidently still takes place in human babies at the age of about six months.
It is said that the human neocortex makes up 80% of total brain size, compared with 70% in the case of the chimpanzee. This 10% growth in the neocortex may represent the explosive mutation which produced the postconscious faculty although it does not appear to be a large enough cause to produce so significant an effect. The diagram in Figure 7 below is not meant to indicate so large an increase in brain size as it suggests, but to show the dramatic increase in reasoning capacity caused by this mutation. It was not the huge number of additional cells alone which gave us this added capacity but the fact that they made up a separate, higher faculty which afforded optimum reasoning potential. So we can explain the apparent fact that the brain of Neanderthal man was larger than the human brain if we assume that the former lacked the latter’s six cortical layers.
I do not insist on this theory of the emergence of the human species by sudden mutation but it is the most likely that I have been able to deduce and it nicely explains subsequent developments.
The postconscious has its own memory, entirely separate from the old system of comparative judgement which obeyed a fixed set of instinctive ‘do’s’ and ‘dont’s’. It had to be so because the apefolks’ troubles came from using their higher intelligence to pursue the drives of instinct too far. It was now logical that responsibility for life should be taken away from blue-prints evolved out of the past and given to patterns arising from reason. The faculty grew to its full capacity, presumably somehow knowing to stop growing when the evidently optimum figure of 10 to the power of 11 cortex cells had been reached (the restricted capacity of the cranium is unlikely to have limited further growth, for that would mean that its limits exactly coinciding with this optimum figure.) Presumably the postconscious started work on its most urgent task, that of formulating an alternative motivation and code of behaviour and pressing it on the self in place of instinctive consciousness. A hundred thousand years later it is still at work but, for reasons which I shall try to explain, it has made little progress.
The most significant feature of developing life has been its rising level of intelligence. Yet, although instinct, the preconscious, and consciousness have produced complex animals, these can hardly be said to be vital developments, since primitive life would have flourished without them. The human mutation has resulted in the most complex developments of all, changing the face of Earth, yet we are less happy and contented than the apes we sprang from. That mutation was the birth of intellect, the significance of which we do not appreciate because we have not fulfilled its true potential. We have developed many skills to a high degree, such as language – a greater stimulator of mental development than manual dexterity – and the many arts and means of communication, but we have failed to do that which is best for us and our world. Human intellect has not grown to maturity, but is still a child.