Brain and Intelligence

As you read the words on this page, you are utilizing thousands of the 100 billion (more or less) nerve cells, called neurones, that make up your brain. The electrical firings and chemical messages running between these cells are what produce our thoughts, feelings and interactions from the world to inside us and to the world from inside us.

One hundred billion neurones may seem like a lot of neurones, but this is actually only about 20% of the number we originally start with at birth. The number of neurones in our brain peaks prenatally and then they start to prune themselves out, one by one, through childhood. By the time we enter adolescence, our brain has chosen the final selected neurones it will keep throughout our adult life. The decision is based on which cells we use and which we do not. The cells we do not use are pruned away leaving more room to add branches, or dendrites, to the neurones that we do use. New branches are added as the brain receives and processes any new information.

According to Charles Darwin's theory of evolution (see the the origin of species, the descent of man, and the voyage on the Beagle), a theory now widely accepted and developed in the scientific community, we are the result of billions of years of evolution from lower forms of life by a process of natural selection and retention with increasing complexity... As such our species "homo sapiens" is believed to have evolved to the stage that we evidence today, some 45000-100000 years ago, or much less than a mil../geology/lion years ago. Since there is scientific evidence that life on earth started 3-3.5 billion years ago, ie. approx. one billion years after the earth was formed as a satellite of the sun, and the first complex forms of life as shown by geologic evidence appeared some 600 million years ago, the process of evolution which lead to "homo sapiens" took about 3.5 billions of years...

The human brain is the best organized, most functional 1.5 kg of matter known on earth. Our brain, our most complex organ, is the result of eons of biological and genetic evolution. It permits us to perceive the outside world, act and react in it in all circumstances, adapt ourselves to, and solve, many problems and difficulties that we encounter throughout all our lives. Although, biologically, our brain may still be in the state it was 45000 years ago when our environment was dramatically different, because of our capacity to adapt, we have, collectively and individually made fantastic progress in what may be called our cultural evolution. Obviously, cultural evolution is much faster than biological and genetic evolution. In 45000 years, we have taught ourselves how to keep the fire, we have invented the wheel, as well as all our tools and implements; it has lead to our transition from the state of hunters and collectors to the state of sedentary agriculturers; we have learnt how to use seeds and plants and to domesticate animals for our food; and in the last millenium, we have made still faster progress: the renaissance, the enlightenment, Bach's music and the barocco period, the Sixtine Chapel, Shakespeare and Hamlet, Beethoven's Ninth Symphony, we have invented the steam engine, electricity, the automobile and the jumbo jet plane, the apple pie, the game of golf, computers and the internet, TV and DVDs and a whole lot more, but also we fought the first and second world wars devasted Europe and the far East, we perpetrated the holocaust, and we blasted and tore down the World Trade Center...

Our brain's most remarkable feature is its capacity of acquiring language at a very early age (2.5-3.5 years); this permits us to communicate with other men, to undertake collective actions and to acquire knowledge and know-how.

Our brain was probably a small advantage of our species that enabled us to survive until the age of reproduction, in the difficult environment that prevailed when all species were in equilibrium in planet earth. But this small advantage became enormous because it gave us the capacity of exchange through language, thus enhancing our brains by cultural evolution. In the course of the thousands of years that have elapsed since we first appeared on the planet with this small advantage over the other species, we have overpopulated the earth, and we are progressively driving out many of the other species by destroying their habitats. Obviously, this is incompatible with the limits of the planet and someday we will collapse.


Mis en ligne le 12/08/2003 par Pierre Ratcliffe. Contact: (pratclif@free.fr) sites web http://pierreratcliffe.blogspot.com et http://paysdefayence.blogspot.com