The brain develops in the foetus during pregnancy and it is largely composed of nerve cells or neurons. These cells divide at the astonishing rate of producing about one million new nerve cells every five minutes so that at birth, we have about ten, thousand million of them. Although a few animals have larger heads and brains than ours, such as the whale and elephant, they do not have as many neurons as we do. The adult human head and brain is larger than that of a baby, but this increase in size is not due to an increase in the number of nerve cells. This is because our brain nerve cells are genetically programmed never to divide after birth so the observed increase in brain size is due to the growth of other cells in the brain and the increase in the number of connections between brain nerve cells. The fact that adult brain nerve cells cannot divide is a condition unique to the brain. Every other cell or tissue in the body has the ability to divide which gives the tissue the ability to repair if damaged. But because the brain nerve cells cannot divide, the brain can not always repair in life which is a big disadvantage. Why should this be so ? Recent thinking proposes that the advantage of the nerve cells not dividing is that our brain remains largely the same throughout our entire life, which may give us the feeling that we are always the same person, irrespective of our age.
The brain is not a single giant ‘silicon chip’ with all the nerve cells doing everything. Instead, different regions have evolved to have specialised functions so there are areas dedicated to allowing us to move and others that allow us to hear, taste, smell, feel and see. In fact, in the case of vision, there is not just one special ‘visual’ region – there are more than forty ‘sub-regions’ each providing a particular aspect of vision. For example, one sub-region provides colour, whereas another provides motion and another allows us to see the subtle differences between human faces. Without this latter region, we would all be ‘face-blind’ and unable to recognise different faces, even our own in a mirror ! Other regions provide us with memory and emotions, and yet more regions are dedicated to language and speech. No other creature alive can truly ‘speak’ and this is one of the highest qualities we have.
The young brain has to learn how to hear, smell and see and it is rather like clay thrown on to the wheel by a potter. The potter moulds the clay in to a work of art and similarly, bombarding our brain with sounds, tastes and images in early life shapes and moulds our brain in to a structure with working senses. Without this early bombardment, our senses would not work correctly and we might not be able to speak or understand spoken language.
Our closest relative, the Chimpanzee, has DNA that is about 95% the same as ours and yet the animal is very different from us. It’s brain is only about one quarter the size of ours and our brains are much bigger due to the massive enlargement of the front of the brain, our frontal lobes. This part of the human brain gives us intelligence, personality, drive, motivation, planning and higher emotions such as love. It allows us to appreciate ‘art’ such as the work Leonardo da Vinci and the music of Mozart. We also know about life and death and we are self-aware, ‘I think, therefore I am’ and no other animal has this particular capacity, except perhaps some primates, whales and elephants. Our sophisticated brain gives us the ability to create things with our minds and hands which has allowed us to put a man on the moon. We have a growing understanding of the structure of the Universe and the structure of atoms and no other creature comes close to this level of knowledge.
All this emerges from a structure made of water, salt and a few minerals which has taken a few thousand, million years to evolve. Nothing is known to be more complicated and what an incredible structure it is that only weights about one and a half kilograms and has a surface area about the size of a sheet of A4 paper. Neuroscience has learned much about the brain over the past century, yet the language of the brain itself is still not completely understood or how ‘consciousness’ is generated. How will the human brain evolve in the next million years ? It is likely to get bigger and perhaps we will be able to sense dimensions and energies presently unknown to us.
