Background
Various sociological theories, such as the theory of differential association by Edwin Sutherland and the theory ofOverview
Sexual selection
First, ENA theory posits that women value the social position and resources of a prospective partner more so than men. Therefore, there is a large evolutionary incentive for men to compete and obtain the aforementioned social status and resources. Thus, males have evolved greater competitive behavior, which could manifest itself in criminality depending on the behavior's position on the crude-sophistication scale.Biological changes in males
Ellis hypothesized that the aforementioned selective pressures led to changes in the male brain that is mediated by a substantial increase in the presence of androgens (male sex hormones), particularly testosterone. During puberty, testosterone levels spike, producing three changes identified by ENA theory to play a crucial role in competitive behavior. The first change is in lowering the sensitivity of the male brain to adverse environmental stimuli. This change has the dual role of decreasing sensitivity to pain and keeping the brain in a suboptimally aroused state. Thus, men will tend to seek more sensory stimulation while being more resistant to the pain that behavior might elicit. The second change caused by testosterone is alterations to theBehavioral manifestation: the crude-sophisticated spectrum
Competitive behavior does not necessarily constitute criminal behavior. To distinguish those behaviors that are more likely to be criminal versus more benign behaviors, Ellis proposed the crude-sophisticated spectrum. Crude behaviors are those that are obviously and purposefully harmful (e.g.: rape, murder, etc.) while sophisticated behaviors are those that still compete for status or resources but are generally considered acceptable by society (e.g.: competing for a promotion or political position). Many behaviors lie between those two extremes. For example,Evidence
Evolutionary pressure and testosterone
Several lines of evidence point to females selecting for males with greater access to economic resources. Ellis points to a cross-cultural study of 37 different cultures which found that women universally preferred men with greater financial prospects more than men did. This trend is also reflected in the personality traits that women prefer, with women preferring ambitious and industrious men in 29 of the 37 cultures sampled. A study done on mate selection in a primitive Tanzanian hunter-gatherer society showed that those women valued men's foraging society, indicating that these women also valued their mate's access to resources. Evidence also shows that these preferences translate into actual mating behavior, with recent studies showing that women tend to date and marry men with higher incomes. Various studies have found that salivary and blood testosterone levels are correlated with criminal behavior. One study on over 600 prisoner inmates found that salivary testosterone was higher in prison inmates who were convicted of more violent crimes and who violated more prison rules. In a 2014 study performed by Ellis, the 2D:4D ratio was used to indirectly measure fetal testosterone levels, which the researchers then used to correlate with criminality. The study found that increased fetal testosterone levels were moderately correlated with the likelihood of committing a variety of different types of crimes in both men and women.Crude-sophisticated spectrum
ENA theory predicts that as males transition from adolescence to adulthood, they learn to manifest their competitive behavior in a more sophisticated fashion, thereby decreasing criminality. Therefore, ENA theory would predict that those who have a greater learning ability would be able to make the crude-sophisticated transition faster and will exhibit less criminal behavior. Ellis points to evidence that there is a moderate inverse correlation between IQ and the probability of offending. He further looks at research which shows that learning disabilities are directly correlated with juvenile delinquency. However, he notes that more research is required to understand the effects of different types of intelligence on criminality and that the existing research is largely correlational.Criticism
One of the central pillars of ENA theory is that fetal testosterone levels cause permanent changes in male brains that lead to increased criminality later in life. However, while individual studies have provided strong results on the effect size of fetal testosterone on aggressive or violent behavior, meta-analyses have remained less conclusive. A 2017 meta-analysis of fetal testosterone levels found that fetal testosterone levels (measured by the 2D:4D digit ratio) had only a small effect size of 0.036 on aggressive or violent behavior. The authors further concluded that "the 2D:4D digit ratio is neither strongly nor reliably related to aggressive or violent behavior". Other researchers have also pointed out the fact that the 2D:4D digit ratio, which is the method most often used to relate prenatal testosterone to future behaviors, is a rough and unreliable measure of prenatal testosterone. A 2012 analysis failed to replicate previous findings that a lower 2D:4D digit ratio correlates with increased androgen production. The authors of the analysis then hypothesized that androgens only have a slight effect on the 2D:4D digit ratio, and that variation in that ratio could arise from a number of other genetic or non-genetic sources. Lee Ellis has responded to some of these criticisms in a 2018 commentary published in the journal '' Aggression and Violent Behavior.'' First, he agrees that the 2D:4D digit ratio is a crude measure of fetal testosterone levels, but that it is still a useful one. He then offers a few alternate methods of fetal testosterone measurement that could be used in future studies. Regarding the meta-analyses questioning the relationship between fetal testosterone levels and criminality, Ellis argued that the meta-analyses included traits that did not have known sex differences, therefore diluting the actual effect size of the relationship with traits that should not be related to fetal testosterone levels.{{Cite journal, last1=Ellis, first1=Lee, last2=Hoskin, first2=Anthony W., date=2018-09-01, title=Status of the prenatal androgen hypothesis after two meta-analyses reported little support: A commentary, url=http://www.sciencedirect.com/science/article/pii/S135917891730352X, journal=Aggression and Violent Behavior, language=en, volume=42, pages=29–34, doi=10.1016/j.avb.2018.06.005, s2cid=150091539, issn=1359-1789References