ABSTRACT
In this chapter, attention will be given exclusively to variables for which consistency scores of 95.0 were found for at least one age group. These variables will be considered one-by-one with a goal being to decide if each variable should be considered a universal sex difference (USD). Because ENA theory has both evolutionary and neurohormonal components, it goes beyond sexual selection theory to predict that androgens are contributing to sex differences in height and body size. Studies have indicated that joint laxity is associated with ligament injuries following strenuous athletic activities. Fifty-six studies were located having to do with sex differences in skin color. The pertinent research has been conducted in 16 different countries plus one multi-country study, published over a 55-year time frame. Many studies have reported on sex differences in the size of the brain, most of which are based on samples of adults.
