Studies of identical twins suggest that approximately % of aggressive behavior in the population can be explained by genetic factors, although the specific genes that underlie this effect have not been isolated.

Studies of identical twins suggest that approximately 50% of aggressive behavior be explained by genetic factors. This implies that a significant proportion of gender differences in aggressive behavior results from an interaction between environmental factors and genetics. In addition, researches have noted that boys tend to be more aggressive when raised in nonindustrial societies; patriarchal societies, in which women have less power and are considered inferior to men; and polygamous societies, in which men can have more than one wife. 

Calcinosis is the diagnostic term that means an abnormal buildup of calcium on the kneecap (patellar) surface. it is a term uses to describe a group of disorders in which calcium deposits form in the skin. it is also referred to the abnormal deposit of calcium phosphate.