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As our distant ancestors started to make better use of their brains so, over long periods of time, human brains got larger so forcing the skull to get bigger. So large did the skull become that the birthing process became more difficult and more problematic for humans than any other mammal. To ease the process humans give birth to their young when their brains are still tiny – a mere forty percent of their full structural form.
How is it, then, that if we have such premature brains we go on to become the planet’s pre-eminent learning species? Evolution has turned what seems to be a horrible disadvantage into a massive benefit, and in so doing created the conditions that have resulted in thinking, talking, contriving, thrusting and argumentative Modern Man. It goes like this. Mammals whose young develop almost exclusively within the mother’s womb are born equipped with all the instincts they need to survive – there is little they need to learn1. Because humans developed empathetic skills (the understanding of a neighbour’s thoughts and intensions through our ability to “read their faces”) maybe as long ago as one and a half million years they needed brains large enough to hold vast quantities of data2.
With the advent of spoken language in the last one hundred fifty thousand years, the skull has again expanded. Being born only nine months after conception (rather than the twenty-seven months which is the theoretical time it would take for the brain to reach maturity within the womb) human babies are infinitely more dependent on cultural interaction outside the womb to stimulate subsequent brain growth than are those mammals whose brains are pre-eminently shaped by instincts before birth3.
Being born so premature means that human babies are extraordinarily vulnerable, which has put pressure on mothers-to-be to find mates who will stick around long enough to help succour the young – the evolutionary basis for the family unit. (Research in 2005 suggests that the time it takes for a woman to reach orgasm is an evolutionary adaptation that enables the woman to assess whether the man is interested enough in her to trust him as a long-term provider)4. More than any other creature culture becomes very important to humans. Babies can learn more experientially outside the womb than other mammals can ever inherit as instincts. Because cultures change far more rapidly than does human nature, our babies, if they live in a reasonably interactive culture, will acquire a massive “learning advantage” over their nearest animal relatives – the chimpanzees – in the first three years of life.
Consider the eyes of that young baby as it follows your every move. “What’s going on in there?” you wonder5. And well you should, for some seventy or so years later those darting, questioning, eyes may well belong to an Einstein or a Darwin. Now compare that with the lack of contrast between a baby Chimpanzee’s eyes, and a grand old grandfather of a chimpanzee. Something amazing is going on inside the human brain that is not there amongst our nearest relatives.
In those very few ‘Romulusand Remus’6 situations where human babies have been brought up by animals (feral children) such children have none of these cultural advantages, and revert to early Stone Age behaviour. Civilisation rests very lightly on top of ancient instincts.
It’s all there in our big brains. It is they which give us the mental appearance of being travellers from an antique land. Sometimes it feels as if we’re trying to run twenty-first century software on hardware last updated fifty thousand years ago.
Thesis 9: 24th August 2006