Physiology

[Martin Hash]

Evolution works on a simple yes-or-no question: does a trait increase the chance of reproduction? Those characteristics that reproduce thrive, and those that do not disappear. Physical enhancements that affect reproduction are obvious: those who can, did, and their superior advantages are visibly apparent, such as better eyesight or a longer beak. However, psychological traits also contribute to individual procreative success: a well-known example is how aggression in male primates establishes a breeding pecking order. Psychological traits also have a physical origin, usually in the form of chemicals that released into the bloodstream due to a stimulus such as fear or pain. Of the many chemicals that evolution has designed into your body, testosterone, corticosteroids, and endorphins are the ones that most influence your psychology.

Stress produces corticosteroids, triggered by adrenaline, which increase energy production, blood pressure, heart rate, and respiration - the fear response. Those bodies that respond the most effectively to fear are the bodies who survive to produce offspring. Unfortunately, these emergency measures that your body takes to save itself are at its own expense, and cannot be maintained over extended periods. In fact, prolonged stress has long been known to cause people to deteriorate, both physically and mentally.

Endorphins are your body’s relaxation mechanism. They are produced to calm you after you are excited, after sex, and if you are injured they numb your pain. Again, these activities are very important to your body’s survival, and again their release is only in short bursts because the long-term effect of endorphins are decreased mental acuity, muscle atrophy, high blood pressure, suppressed neuron expansion, and reduced resistance to disease.

Testosterone is the chemical in the body that stimulates your body to action, whether it be aggressive or flight. Survival and the ability to mate and protect a mate are directly affected by the body’s release of this essential chemical in both males and females, and it is the ultimate progenitor of a society’s pecking order. There are many examples in nature of the health benefits of testosterone: increased cardiovascular activity, prevention of osteoporosis, increased muscle and bone mass, and higher antibody count. Psychologically, love and fatherhood decrease testosterone levels in men resulting in psychological reorientation to paternal care rather than risk-taking. These chemicals often work to counterbalance each other. For example, testosterone-driven males would fight each other to a counter-evolutionary standstill, but luckily endorphins smother those aggressive tendencies in the less-strong male so that it will subordinate itself, preserving the species.