Monday, September 12, 2005

Heads and brains

Dr. K. Rohiniprasad

In Conan Doyle’s story The Blue Carbuncle, Sherlock Holmes comes across a large hat and deduces correctly that the owner must be an intellectual. But the size of the brain is not necessarily related to intelligence. Albert Einstein had a normal brain mass. Byron, the English poet, Oliver Cromwell the 16th century politician and Ivan Turgenev, the Russian novelist all had a brain mass of 2200g while Anatole France, the French writer who was no less brilliant, had only 1100g brain mass. However, “microcephalics” who are born with brain masses between 500g and 900g are mentally challenged. Most modern humans have a brain volume of between 1300 and 1500cc. Orientals have slightly larger brains compared to westerners.

Much of the human ability stems from the large size and complexity of the human brain. Unlike other mammals, giving birth to offspring is a very painful process for human beings. The difficulty in giving birth as the baby is expelled from the uterus through the birth canal is mainly due to the size of the baby’s head. The head is relatively small at birth but is still large compared to any other animal. Babies are born with a brain mass of about 350g that grows to 500g by the time they are one year old.

As human evolution progresses, the baby’s head is bound to get larger and larger at birth. While it was performed only in difficult and rare cases in earlier days, giving birth by caesarean section is much more common today. This is probably a sign of continuing evolution in brain size going hand in hand with advances in surgery and may soon become the norm.

While the mother suffers intense labour pains, emergence through the birth canal is very traumatic for the baby also. Some say that the compression experienced by the baby’s head releases some toxins, the effects of which remain forever. The shock of suddenly entering a bright, dry and cold world out of a warm, wet and dark womb is very profound. Our idea of death as a ‘release’ and the reports of seeing light at the end of a dark tunnel by people with near-death experience may also be perhaps related to this trauma, according to some authors.

In the adult human skull the cranial region is the portion of the skull directly surrounding the brain. The human brain is full of folds and convolutions and fits snugly into the skull that protects it. Even today, the incomplete closure of the skull at birth shows imperfect accommodation to the evolution of larger brains. After a blow to the head, a person may be stunned or dazed. He may become unconscious for a moment. The concussion usually leaves no permanent damage. If the blow is severe, haemorrhage and swelling can occur. Depending on the area of the brain affected, the victim may suffer severe headache, dizziness, paralysis, convulsion, or even temporary blindness.

Anthropological evidence shows the growth of brain in size over the millennia as primates and hominids evolved into modern humans. It is interesting but not surprising that as the cranial volume of hominids increased spectacularly the pelvis also began to alter in shape to permit the birth of babies with larger heads. Even today, compared to boys’ girls have wider pelvises that grow further with age. The evolution of the human brain as mankind progressed from hominid stage to the modern era is an interesting topic in itself that we will examine in the next article.


Post a Comment

<< Home