Race Differences in Aggression

The following post is going to overview the evidence concerning race differences in aggression and outline possible explanations.

1: A Review of Race Differences in Aggression

A large survey of evidence is available both showing the outcomes of racial differences in aggressive behavior, as well as predictors of aggressive behavior, and of course simple tests of aggression itself. For example, we can look to estimates of criminal behavior such as The Color of Crime 2016, tests of anti-social behavior such as the Minnesota Multiphasic Personality Inventory, and simple psychometric tests of aggression. We will look at each below. Unfortunately, most of the literature is focused on whites and blacks since these are the most easily sample-able groups and the most relevant in America. Hence, the following sections will also focus on black-white differences, but Asian-white differences tend to be self-evident.

1.1: Psychological Tests of Aggression

Starting with the last one I mentioned, psychological tests of aggression, plenty of studies focus on racial differences. Marcus (2007) is a popular piece of literature concerning aggressive behavior. Marcus uses YRBS data to show gender and race differences in aggressive and violent behavior. The results are abridged in Table 1 below. Unfortunately, we only see data on blacks, whites and hispanics here, but nonetheless, there are clear differences – in every category, blacks display more aggressive/violent behavior than whites, in some cases, 2 times as great.

Concerning the previous data, Marcus says,

“Blacks showed from 13% to 78% greater involvement than Whites for all forms of aggressive and violent behavior, whereas for feeling unsafe at, or to or from, school showed 123% more Blacks felt unsafe than Whites. Racial-ethnic differences of this magnitude have been reported in other national surveys that were roughly similar.”

A large survey of seniors in high school was done by Johnston et al. (2008) and found that blacks self-reported being about 10 percent more violent than whites, based on various questionnaire results. These results likely understate the actual disparity between whites and blacks because of the higher black rate of lying on questionnaires and in general (see Section 1.2).

Hartup (1974) had a group of observers rate children on their aggression levels. Particularly in instrumental aggression, older black children were more aggressive than older white children. There was likely difference in hostile aggression as well, but it was not detailed. There was a Race x Age interaction – the differences between whites and blacks were small at a younger age and grew as the groups were older.

Intervention programs may have some effect on childhood aggression, however it doesn’t appear to diminish race differences, and is differential in its treatment towards race. An experimental study reported on the effect of a treatment program towards lowering aggression across races. These results were also consistent across the sexes (Hawkins et al. 1991). I’ve created a table of the aggression data below:

In literature on aggression, researchers typically distinguish between proactive and reactive aggression. The former is essentially a dominance complex – individuals seek out goals vigorously. The latter is related to our more colloquial sense of the word – hostility, anger, and violent behavior towards individuals (see Walters, 2005). A study by Mayberry and Espelage (2005) looks at both in blacks and whites. Unlike Hartup (1974), they find the aggression differences between blacks and whites are larger in reactive aggression (the hostile component). If we average the means and SDs for black females and males and white females and males, and we use the white avg. SD (which is very similar to the black avg. SD), then we find black people are 0.5833 white SDs higher in reactive aggression than whites are. This is certainly large enough to be consequential.

Wells et al. (1992) looks at teacher and self rated aggression in students. They find that black males were nearly twice as aggressive as white males and that black females were nearly four times (!) as aggressive as white females. This is one of the few studies which also reported Asian American results as well – as we may expect, Asians were far less aggressive than both of the other groups. This is all after controlling for socioeconomic status.

As far as qualitative evidence goes, Levin (1997) covers multiple sources which reveal a widespread sense of greater aggression in blacks and greater calmness in Asians. In another classic in literature on race differences, Black and White Styles in Conflict, Kochman (1983) provides evidence that blacks may be more aggressive than whites are. Regarding argumentation style, Kochman says that the white debate style is “low-keyed: dispassionate, impersonal and non-challenging . . . cool, quiet and without affect”. Conversely, the black argumentation style is, “high-keyed: animated, interpersonal, and confrontational . . . heated [and] loud. . . . Blacks do not simply debate an idea [the white mode]: they debate the person debating the idea”. When responding to violent situations, Kochman also reports that blacks have a greater threshold for aggressive situations, saying that black people tend to require a higher level of violence or aggression for a situation to be considered serious to them.

So, from what we can tell, the races do differ in self-reported and peer-rated aggression levels, and qualitative descriptions tend to match with quantitative analysis.

1.2: Anti-Social Behavior and Psychopathy

Anti-social behavior (ASB) is a useful measure of aggression inasmuch as the ASB predicts or contains aggressive behavior. While I entirely acknowledge that the two are not the same thing (see Marcus, 2007), ASB is certainly a useful predictor.

One of the most important studies on this topic comes from Richard Lynn (2002). He used data from the Minnesota Multiphasic Personality Inventory (MMPI) and standardized the data around a white mean. Scoring higher on the MMPI indicates antisocial, psychopathic behavior, whereas lower would correspond with the opposite. The test uses measures such as if the participant lies on the test, depression, schizophrenia, etc. In Table 3 I’ve summarized the mean results:

The criticisms of this study (see Skeem et al. 2004 and Zuckerman, 2003) were really bad and for a good response to them, see Lynn (2003). Lynn also uses measures of ADHD, crime, etc. to further back his argument.

A meta-analysis by McKoy and Edens (2002) further back Lynn’s argument, however they find a considerably smaller difference between the races. They also report that the results were largely heterogeneous. They were largely limited to samples of incarcerated or institutionalized individuals, the latter sample issue is criticized by Lynn (2003).

Kirkegaard (2018) finds that being black predicts higher levels of anti-social behavior, though this relationship was statistically insignificant (which may be due to response bias). Lynn (2002) and Lynn (2003) review evidence which suggests the races differ in anti-social behavior.

Levin (1997) provides a comprehensive review of racial differences in values, temperament, and intelligence. He cites evidence showing that black people are more likely to respond to specific statements regarding behavior and values, which are not in line with typical “white values”. Blacks agree more frequently with the following statements than do whites:

“I am an important person.
It wouldn’t make me nervous if any members of my family got into trouble with the law.
I am entirely self-confident.
If given the chance I could make a good leader of people.
I have often had to take orders from someone who did not know as much as I did.
Most people will use somewhat unfair means to gain profit or an advantage than lose it.
Most people make friends because friends are likely to be useful to them.
Most people are honest chiefly through fear of being caught.
It is not hard for me to ask help from my friends even though I cannot return the favor.
I am sure I am being talked about.
It wouldn’t be better if almost all the laws were thrown away.
A person shouldn’t be punished for breaking a law that he thinks is unreasonable.”

Levin continues, saying, “These responses are interpreted to reveal greater cynicism, mistrust, conflict with authority, and “externalization of blame for one’s problems”… Race differences in MMPI scores diminish when social status, IQ, and level of education are fixed, but once again this does not show MMPI differences to be status artifacts. Traits that affect scores may also affect status, as for instance friction with authority impedes advancement in hierarchies.” These tendencies tend to reflect some anti-social behavior in black people.

1.3: Criminal Behavior

We can also use criminal behavior as a proxy for measurement of race differences in aggression. This method indirectly tells us about the average violent/anti-moralistic behavior of each race. However, there is a caveat to traditional crime statistics. The FBI Uniform Crime Report, the most often cited source of crime rates by race, state, age, etc. is flawed in that it records people as having Hispanic origin if they are a victim, but not if they are a perpetrator. If they do happen to be the latter, they are counted as white, and since Hispanics tend to commit more crimes than whites, this will inflate the white crime rate. This phenomenon is called the Hispanic Effect.

du Lion (2000) used INTERPOL and NCVS data to calculate race differences in aggression, standardized by a white average. Whites scored 0 as their mean was used to standardize the data set. Blacks were 0.37 SDs higher in aggression/criminality than whites, and Asians were 0.24 SDs lower in aggression/criminality than whites. A third of a standard deviation may not seem massive, but it is particularly important at the tails of the bell curves. Because of the difference in means between groups, we find exponentially larger differences in the extremes. Unfortunately, at the time of this data, the Hispanic Effect was still a problem in NCVS data hence we are actually overestimating the white mean and therefore underestimating the black-white difference.

Rubenstein (2016) used survey data from New York City, Los Angeles, and Chicago to calculate the black, Hispanic, and Asian multiples of white crime rates. In virtually every criminal category, blacks were much more criminal than whites. This was persistent in each city. Even Asians were considered to be more criminal than whites, but my guess is this is because of a higher proportion of Chinese people in bigger cities. This study was able to avoid the Hispanic effect, and therefore give us a much better estimate. Additionally, they find that arrest rates matched incarceration records, implying that there was little to no racial bias in the criminal justice system. Similar results were found in a previous edition, titled The Color of Crime 2005 (Rubenstein, 2005).

Beaver Ellis and Wright (2009), in their large review of causes of crime, find that blacks do commit more crimes per capita than white people do. Lynn (2002) also uses national crime rates as a method of measuring race differences in aggression and finds the typical result – blacks are most aggressive, Asians are least aggressive, and whites are down the middle.

From all of the previous evidence, spanning from peer-reported aggression to anti-social behavior to crime rates, we find considerable evidence that the races differ in aggression. Whites appear to be down the middle, with Asians lower in aggression (though, we are limited in peer-reported aggression of Asians), and blacks being the most aggressive.

2: Environmental Explanations

Some environmental explanations are regularly offered for the racial differences in aggressive behavior, but most if not all, either fail to explain for a large portion of the variation between races, or are entirely a function of the sociologist’s fallacy (or both).

2.1: SES, Poverty, Education

The most prominent explanations for the race differences in aggression are based in socioeconomic status (SES), poverty, and education. Since black people tend to do worse in all of these categories and happen to be more aggressive, and the fact that these variables are all correlated, we may find this to be a reasonable hypothesis. There are two main counters to this hypothesis. The first is that even if all of the previous-stated conditions are true (arguable), we can show that blacks and whites in the same SES will still differ in aggressive behavior. The second is that conditions such as SES, poverty, and education are not an end-all be-all – in fact, these variables are largely predicted by genetic variables.

I’ve already expanded upon evidence to support my first notion. Earlier I cited both Hawkins et al. (1991) and Wells et al. (1992) which show that, even when holding SES constant, the races differ in levels of aggression. In the former of those, they show that an attempt to increase future SES, by method of intervention programs, actually increases the racial gaps in aggression, despite lowering the overall levels of aggression, at least in males.

Increases in socioeconomic status seem to provide different outcomes for blacks and whites. Blacks see less financial return from increase in SES than whites do (Wilson, 2007), and multiple studies have shown that black people don’t receive the same health benefits that whites do with comparable increases in SES (Geronimus et al., 2001; Farmer and Ferraro, 2005; Shuey and Willson, 2008). The explanation for this phenomenon is typically put through the lens of racism/systemic discrimination, segregation, etc. (see Boen, 2016). However, accusations of racism need definitive evidence and since white Americans are not particularly racist and haven’t been for a long time (see Last, 2019), we can argue that at least in America, racism is an unlikely suspect. Of course, America is not the only area where race differences in aggression exist. For example, in Lynn’s paper (cited earlier), he cites a Japanese study of MMPI results. Of course, most people understand Japan is a racist country, however the racism is more directed to anyone who is not Japanese, aka both blacks and whites. Despite this, the racial disparity continues to exist. Perhaps, blacks make worse use of their increase in SES on average, or there is another genetic argument to be made here, but suffice it to say, racism is unlikely the main cause.

Regarding the sociologist’s fallacy: white-black differences in IQ are largely a product of genetic differences between the groups. Yes, this statement is controversial in the mainstream world, however the position is not set and stone among researchers. I will elaborate on this claim more in Section 3.1. Since heritable IQ expresses itself into the environment, creating a gene-environment correlation, our socioeconomic outcomes are largely predicted by genetics. Herrnstein and Murray (1994) and Palmer (2018) both found that IQ is a better predictor of an individual’s poverty level than family socioeconomic status. Another major important finding from Herrnstein and Murray is that the far majority of racial gaps in poverty and in criminal behavior are made up for if we control for average IQ differences between the groups. Hence, if we accept that genetics explains part of the gap in intelligence, that crime and IQ are correlated (see Jeffrey, 2019) and that IQ and poverty are correlated (see Herrnstein and Murray), and that race gaps in crime and poverty are largely made up for by IQ, then it is not an unreasonable conclusion that race gaps in aggression and in poverty are based in genetics. I will go into this argument more in Section 3.1, as this is purely to further explain the sociologist’s fallacy.

Education is also a function of the sociologist’s fallacy: people with higher heritable IQ seek out better environments and therefore better schools. Beyond this argument, we can look at how blacks and whites have the same educational opportunity (Last, 2019), blacks receive more funding than whites do (Richwine, 2011), and even if we posited that education and crime are strongly correlated, educational attainment is largely a function of IQ and thus, there is a large confounding. Hence, this argument is all-around just wrong.

As a final note, the interaction this section is refuting is purely correlative, rather than based in causation. It is easily the case that people who have worse temperaments and higher levels of aggression are going to create worse environments for themselves, for their kids, and in the future, pass “high aggression” genes to their kids (see Section 3.2).

2.2: Single Motherhood

Single motherhood is the response most often given by conservatives in regards to disfavorable outcomes in black communities. While single motherhood is certainly a negative and is not entirely explainable by IQ differences (see Herrnstein and Murray), the data on single motherhood, crime and aggression, is less cut and dry than one might think.

For example, a meta-analysis of meta-analyses by Petrosino et al., (2009) found correlations between single motherhood and crime of .07, .09, .09, .10, and .10. The effects of single-motherhood and criminality were statistically weak. The study failed to find many other large correlations between single motherhood and outcomes.

Montatre and Boone (1980) finds the effect is differential towards different races. Whites react positively towards having both parents in the home, whereas black people actually react positively towards single motherhood. Hence equalizing the single motherhood rates between whites and blacks could potentially increase the crime disparity between the two (this is not to say that there aren’t other immense benefits to having a father in the home).

2.3: Lead

Lead is the only environmental effect which I consider to be significant in predicting aggression differences in the races, independent of genetic causation. While the fact remains that people with lower heritable IQ and worse temperament will find themselves in worse environments, the effect of lead is large enough on social and medical outcomes, that these effects would be exponentially multiplied.

The literature on lead and aggression/crime is very cut and dry. Since I don’t want to repeat all that has already been said, I simply recommend checking out a good review from TAH.

3: Genetic Causes

As I explained, many of the previously explained environmental causes do fall under genetic explanation. Aside from those, I believe that genetic differences between the groups on their own are a primary explanation for the differences in aggression we see between the groups. I hold this position because of a) the relationship between aggressive behavior and IQ, whose between-group heritability is also high, b) the non-likelihood of an entirely environmental explanation for race differences in aggression and c) the relationship between various race-specific factors and aggression. All will be reviewed below.

3.1: Intelligence, Aggression, and the Jensen Argument

Most people agree the races do differ in their IQ test scores; the main question is whether or not the gap itself is genetic (and some argue IQ tests are invalid, which is entirely false). The entirety of this discussion would not fit into a minor blog post, so if one wants to familiarize themselves with the topic, there are some short papers they can read such as Kirkegaard (2019) or Rushton and Jensen (2005), or great books which either focus on the topic or spend a good deal of time on it such as Levin (1997), Jensen (1998), Jensen (1973), Herrnstein and Murray (1994), Rushton (1997), Flynn (1980), Lynn (2015), etcetera (these are just off the top of my head).

The majority of evidence leads us to believe that the race gap in IQ is between 0.8-1.2 SDs, at an average of 1 SD, and that this race gap has persisted for the last 100 years (see Shuey, 1966; Levin, 1997; Herrnstein and Murray, 1994; Rushton and Jensen, 2005; Chuck, 2013), despite major increases in socioeconomic advancements for blacks, the rise of affirmative action programs and civil rights policy, and the decline of “racism”. This on its own is a major argument for the high heritability of racial gaps in intelligence; despite the secular increase in IQ scores, the race gap has stayed the same (for those who are unaware, the Flynn effect is only on specific skills which IQ tests tend to pick up, whereas the race gaps are on a general factor called g which encompasses all of innate mental ability; the higher the g-loading of a subtest, the higher the heritability, and also the higher the racial gaps – a full discussion of this will be saved for another day).

In Jensen’s Educability and Group Differences, he made the most famous hereditarian argument to this day, which I will explain briefly here and extend to the argument of race differences in aggression. The argument follows as so:

If the heritability of IQ for both blacks and whites is high, then the a priori likelihood that genetic factors are involved is increased. In other words, the higher the heritability, the greater the environmental differences need to be between the groups for the entire gap to be environmentally caused. There is a mathematical way of finding the environmental gap necessary: if we let E be the change in environments and P be the change in phenotype, then the equation is E = P/sqrt(1-h)^2.

If the average race difference is about 1 SD and the heritability for both races is about 0.8 (80 percent; which is likely an underestimate, see Sesardic, 2005; Panizzon et al., 2014), then the black and white environments must lie 2.4 SDs apart (see Levin, 1997). However, if we correct for the reliability of IQ tests, then the necessary environmental difference increases 3.2 SDs (Jensen, 1973). The likelihood of this is 0.011.

Furthermore, the empirical evidence suggests the racial environmental gaps are not that large. Jensen cites evidence from the 1960s showing that blacks and whites differ in employment rate by 0.33 SDs, family income by 0.8 SDs, living below the poverty line by about 1 SD; in another study (Jensen and Reynolds, 1982), they find the SES difference between blacks and whites is about 0.67. These gaps have decreased over the years, yet the IQ gap has not decreased at all. And of course, this is all without correcting for IQ itself, which makes up a large proportion of the disparities between blacks and whites (Herrnstein and Murray, 1994). As Levin (1997) discusses, blacks and whites hardly differ in any environmental circumstance which may influence intelligence. Hence, there is substantial reason to believe genetic factors are involved in the black-white IQ gap.

That is the primary, fundamental argument for a genetic basis in the black-white IQ gap. My reason for going into this is to further back the argument that race differences in aggression have a genetic basis. A large amount of evidence shows that crime and IQ are significantly related, even when controlling for race, class, and sex (Jeffrey, 2019). Additionally, plenty of studies show the relationship between IQ and aggression (Huesmann and Eron, 1984; Huesmann et al. 1987; Giancola and Zeichner, 1994; Moraga et al. 2019; Seguin et al. 1999; Buelow et al. 2003; Dionne et al. 2003). Even if we are unsure of if the relationship is intrinsic or extrinsic, as has been noted, we can expect that lower levels of intelligence make it harder to understand moral rules and pick up on patterns that build empathy in individuals. Thus, we can honestly make the argument that racial differences in aggression are partially genetic in origin, simply by way of the IQ gap.

Beyond the previous argument, we can apply the Jensen argument to the data I have already provided in order to make a direct case for genes.

3.2: Heritability of Aggression

Table 4 lists a few sources on the heritability of aggression:

The mean result of these studies comes out to 0.566 which we will use in the following section.

3.3: Between-Group Heritability

The point of this section is rather straightforward, considering everything I have covered in this post so far. I’m simply going to use the means and standard deviations provided by Mayberry and Espelage (2005) as well as the mean heritability coefficient of aggression provided before. Since the data is multi-racial, we will use the same heritability coefficient for both races for now, unless newer data arrives showing the races differ in heritability (I suspect black people might have a higher heritability than whites).

The resulting equation, using E as environmental difference, is E = 0.5833/sqrt(1-0.566)^2. Following this equation, E = 1.344 SDs. 1.344 SDs apart is not entirely improbable, but it still falls far from what we would expect in order for the differences to be entirely environmental in origin. More importantly, there is no empirical evidence that the black-white environmental differences are that large. Especially when we hold intelligence constant, black people and white people are in equally nurturing environments, and black people tend to receive greater privileges in the modern world than do whites.

Hence, we have one foundational argument as to why the black-white gaps in aggression have a heritable aspect. In addition, we have one indirect argument, by way of IQ differences. To strengthen the position, I will also provide data on ancestry, skin color, and genes related to aggression which differ between the groups.

3.4: Aggression Genes

If the races differ in allele frequencies which are responsible for higher or lower levels of aggression, then significant evidence is provided that genes play at least some role in the gap.

In an earlier post, I talked about how genes which produce more sweat are likely useful in predicting higher black crime rates. Thompson et al., (2004) finds that the races all carry the CYP3A51/3 polymorphism, however it is only primarily active in Africans/African Americans. This polymorphism regulates sodium conservation, and therefore increases the amount of sweat that individuals carrying an active version of it produce. The fact that it is carried in all races but only active in Africans entails that it originated before the groups spread from Africa and went out of use when the groups who spread experienced colder climates.

Because the polymorphism increases sodium conservation, it tends to raise blood pressure. This is important as blood pressure is significantly related to criminal behavior (Tung et al., 2019). Blood pressure is also correlated with aggression, even when excluding individuals already diagnosed with high blood pressure (Cottington et al. 1985; Jorgensen et al. 1996). A racial admixture hypothesis is supported by Harburg et al. (1973) and Harburg et al. (1978) who both find that, even amongst black people, darker skin is correlated to higher levels of blood pressure. Thus, people with greater levels of African ancestry will have higher blood pressure and we can predict an indirect relationship with criminality (more on this in Section 3.5).

A large body of research has gone into the relationship of serotonin transporters and crime. Serotonin is a monoamine neurotransmitter which mainly increases the impact of emotions, modulates reward centers in the brain, and affects cognition. In a study by Passamonti et al. (2011), they experimentally showed that a lack of serotonin is causally related to higher levels of aggression. The participants were first given a meal that lacked tryptophan, which allowed serotonin to be depleted. The next day, the participants were given the same meal but with a regular amount of tryptophan, allowing the serotonin to be conserved. Both days, the participants were analyzed with an fMRI. Serotonin depletion prevented communication between the frontal lobes and the amygdala, further disallowing the prefrontal lobe to control emotional responses to anger.

The 5-HT neurotransmitter is a popular case scenario of this inverse relationship. A study by Cunha-Bang et al (2016) falls within the orthodoxy and finds that lesser presence of 5-HT neurotransmitters results in higher levels of aggression. However, a variant of this transmitter called 5-HTTLPR is well-known to have a positive relationship with aggressive behavior (see Butovskaya et al. 2018). A large study by Odgerel et al. (2013) finds that African Americans and European-Americans significantly differed in the 5-HTTLPR variants they carried. In relation to white-Asian differences, Noskova et al. (2008) finds ethnic differences between European groups and Asians in the 5-HTTLPR transmitter.

Another popular example is the 2-repeat allele of the MAO-A gene. The MAO-A gene substantially reduces serotonergic function, and has been heavily detailed over the past couple decades. A popular study by Beaver et al. (2014) finds that African Americans who carried the allele were far more likely to commit crimes such as stabbing and shooting. Another study by Roettger et al. (2017) finds that the 2-repeat allele of the MAO-A gene produced delinquent outcomes. Many studies have looked at the allele frequencies for the MAO-A2R and they all find that it is much more frequent among black people than among whites (Beaver et al. 2013; Reti et al. 2011; Choe et al. 2014).

3.5: Skin Color and Aggression

Numerous studies have been done concerning skin color and aggression. This is important as the color of someone’s skin is usually a reliable measure of their racial ancestry; people with much darker skin colors continuously have higher levels of African ancestry, whereas people with lighter skin colors will have higher levels of European ancestry or Asian ancestry. If someone has a greater percentage of African ancestry, the higher the chance they will have a gene or allele discussed in Section 3.4.

For the sake of simplicity, I have created a table of the studies on skin color and various outcomes of aggressive behavior. See Table 5 below:

Clearly, the two variables are substantially related and hence we have another strong argument that racial admixture is predictive of aggressive behavior.

4: An Evolutionary Explanation

For any between-group genetic explanation, we should simultaneously provide an evolutionary explanation as to how those genetic differences came about. Most between-group genetic variation occurs because of differences in environmental pressures between the continents in which each race settled and evolved. These environments pressure some races harder than others and cause specific adaptations to evolve in order to raise fitness for the group’s geography.

In the case of aggression, I believe the differences are best explained through racial differences in r/K strategies. Groups which more r-selected put less care into their offspring, have many more offspring, tend to be more sexually active, aggressive, etc. Conversely, K-selected groups will have fewer offspring and put more care into them. Figueredo (2007) compiled life-history factors into a factor matrix and discovered a “Super-K” factor in which predictors of K life history all positively correlated with one another.

The development of r-strategy in Africans compared to Europeans and Asians is not hard to imagine. Africa’s conditions were much warmer, which may seem like it is creating easier conditions, but it was ridden with parasites and diseases. High levels of diseases caused Africans to need to have more children, in light of high infant mortality (see Rushton, 1997). An interesting study by Ducrest et al. (2008) found that even in animals, darker skin is related to higher levels of sexual activity and aggression. This gives evidence that melanin is an r-selected trait as a whole.

Europeans lived in much colder conditions whereas Asians lived in the coldest area of the world. Colder conditions encourage greater levels of group selection as well as more complex development of social structures. Group selection is related to intelligence (Woodley et al., 2017) and intelligence is inversely correlated with level of corruption in a country, temperature (Lynn and Vanhanen, 2012), and crime (Jeffrey, 2019).

Since African peoples did not need to or were perhaps limited from building proper social structures, and had more reason to act for themselves, it isn’t hard to imagine they developed a less empathetic sense of morality than whites and Asians. (For a full discussion of genotypic explanations for moral divergence, see Levin [1997]). Conversely, colder temperatures encourage cooperation, altruism, and lower levels of aggression.

The inverse correlation between national IQ and temperature is of particular importance as it gives credence to a Cold Winters theory view of evolution. Similarly, body temperature increases higher heart rate and blood pressure, and these ultimately cause higher levels of aggression (Tinga, 2018; Baron and Bell, 1976; Anderson, 1989). Thus, groups that developed in warmer temperatures may already be predisposed to these conditions and become aggressive.

As I discussed earlier, Africans carry a polymorphism which enables greater sodium conservation and allows them to sweat more. This leads to higher blood pressure and may indirectly cause Africans to commit more violent crimes. Each race carries this polymorphism, but it is only active in Africans, hence its usage appears to be a function of warmer temperatures.

All in all, several lines of evidence can be drawn to support a Cold-Winters/r/K selection theory of racial differences in aggression. For another evolutionary explanation, I recommend reading Ryan Faulk’s European Revolution theory.

5: Conclusions

This post has given an extensive review of the evidence of racial differences in aggression and their causes. This is politically and socially relevant as whites are often blamed for the higher prison rates, higher rates of violence, and worse overall conditions of life among black people. We must consider the possibility that this lens is distorting.

First, I presented evidence of the racial differences in aggression. By using specific tests of aggression, measuring anti-social and psychopathic behavior, as well as looking at official crime reports, the results almost unanimously show racial differences in aggression. These quantitative analyses matched with qualitative reports from Kochman as well. By using a wide variety of evidence, it is unlikely racial bias is involved in every result. Some of the studies took proper precautions to ensure that there was as little reviewer bias as possible.

Second, I reviewed some major arguments as to why these differences are environmentally caused. The environmental refutations can almost always be separated into three major areas: 1) x variable doesn’t correlate with aggression as much as its made out to, 2) x variable correlates with aggression, but correcting for it does not close the racial gap in aggression, or 3) x variable correlates with aggression and closes the racial gap in aggression, but the disparity in x between races is largely a function of genetics. These arguments permeate across the available data and make a strong case against environmental explanations for racial disparities. Lead was one variable which I thought was important independent of genetics, however the racial differences in lead exposure have been decreasing whereas the racial gaps in aggression haven’t.

In the third section, I provided a substantial evidence for a genetic hypothesis. I explained the classic Jensenism argument in regards to racial differences in intelligence. Because the racial gaps in intelligence have a genetic component, and intelligence and aggression are correlated, there is likely an indirect correlation at play. I then applied the Jensen argument to aggression itself, taking estimates of the aggression difference between whites and blacks and the heritability estimate, putting it into the equation and showing the final result. From this result, we can conclude it is highly improbable that the racial gaps are entirely environmental. Then to further back my argument, I showed evidence of multiple genes which both cause aggression and differ between races. I ended the section with evidence of the relationship between skin color and aggression.

Finally, I gave an evolutionary hypothesis for the racial differences in aggression. This can be summed up as so: the races diverged from Africa and were exposed to different climatic conditions. Colder conditions encouraged greater group selection and K strategy, whereas African conditions were warmer and had higher rates of disease exposure and parasites. Because of this, the groups evolved different life history strategies and behaviors. Whites and Asians were able to create stronger social structures and Africans were less capable of developing the same moral systems as everyone else. All of this evidence combined makes a strong case for a genetic basis in racial differences in aggression.

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