) Differences in physical strength also have provided for differences in aggression levels between the two sexes. Since men are physically built stronger than women they are more likely to are become aggressive than are women who are not, in general, as physically strong. Neurotransmitters seem to play a very important part in the aggressive nature of mammals. As tested in monkeys, who have matching 99 percent of their genes with humans, it has been found that hyper-aggressive or antisocial monkeys have a deficit of the neurotransmitter serotonin. As an interesting side note the leaders, who have a different type of aggression –assertion—have higher levels of this same chemical. (1) In this same study the monkeys seemed to have very predictable heredity patterns, In which the monkeys were found to easily exhibit the same behavior as the father. This was also found to be true "in men who have been discharged from the Marines for excessive violence, as well as in criminals in Finland who committed acts of wanton violence."(8) Seratonin has also found to be an inhibiting factor concerning aggression. A situation or condition that reduces seratonin levels is among drugs, hypoglycemia. Hypoglycemia is a condition of lowered blood sugar, certain diets can cause or inhibit the onset of this condition, thus directly affecting genetically the aggressive behavior of a person.(12) On the topic of diets an correlation has been found with the corn (a food that decreases the levels of seratonin in the brain) intake of a country and the homicide rates, an obviously aggressive marker.(10) Another chemical in the human machine that causes or has been related to has been the "anger hormone" –adrenaline and its counterpart noradrenaline. This is inherent in the flight or fight reflex, in which fighting is usually prepared by a flush of adrenaline into the system, and anger/aggression are integral parts of it.(12) Stanley Hall found that ...
