NOTE re Brain Function and evolution-part 1

The neo-cortex or “new brain” is the source of rational thought. However, older structures in the brain, also present in reptiles and mammals, still regulate bodily functions and control important aspects of human behaviour without rational thought. They operate subconsciously.

For example, the primitive part of the brain known as the limbic system arose as mammals evolved from reptiles. One of its prime functions was to enable mammals to bond emotionally with their offspring, which, unlike reptile hatchlings, needed longer periods of nurturing to survive to maturity.

This limbic system is the seat of emotions and desires in both animals and humans. It still drives us toward the activities that helped our ancestors survive and pass on their genes by means of a mechanism known as the reward centre. The reward centre comprises several relatively small, interconnected brain structures. Although successful from evolution’s perspective it is also perilous.

1. First, we rely on it instinctively to make daily decisions. It tells us when to eat and drink and which courses of action are likely to prove rewarding – hence its name. Because these urges are subconscious they often go unexamined by the rational mind. They simply feel right and we assume they are our rational will.

2. Second, the top priority of this centre is the survival of our genes – not necessarily our wellbeing, not the happiness of our marriages, and definitely not our moral or spiritual improvement.

3. Third, modern life is vastly different from the life of our distant ancestors. Therefore, this centre’s priorities are often patently erroneous, even though they still feel entirely valid. For example, on a severely over-crowded planet, reckless procreation equates with wretchedness not survival, yet the reward centre encourages it.

4. Fourth, the reward centre does not point the way to satisfaction. In fact, its biological job is to create dissatisfaction, always pushing us from one thing to the next by promising satisfaction. For example, it is programmed to draw us to new mates, or repel us from our current mate, even though trusted companionship is best for health and longevity. Why? To increase the genetic variety of our offspring. In short, we are programmed to be susceptible to temptation.

5. Finally, when the reward centre is intensely stimulated, it subverts our ability to make sound decisions. It overrides our ability to use the neo-cortex to analyse our true circumstances. Then we are vulnerable to exploitation by charismatic leaders (good or bad), religious authorities, politicians, and advertisers.


NOTES:
i. T. Burnham, & J. Phelan, Mean Genes: From Sex, to Money to Food, Taming our Primal Instincts, Penguin Books, 2000.

ii. J. Young, S. De Geest, R. Spirig, M. Flepp, M. Rickenbach, H. Furrer, E. Bernasconi, B. Hirschel, A. Telenti, P. Vernazza, M. Battegay, & H.C. Bucher, Stable partnership and progression to AIDS or death in HIV infected patients receiving highly active antiretroviral therapy: Swiss HIV cohort study, BMJ (British Medical Journal), 328(7430) (2004), 15.