Home » Evolutionary Psychology » “Innate Aggression”? Against the Nature-Nurture Dichotomy

“Innate Aggression”? Against the Nature-Nurture Dichotomy

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Steve Stewart-Williams wrote an article for Nautilus yesterday titled Nurture Alone Can’t Explain Male Aggression. He begins the article by describing a bank robber who shoots and kills a bank teller and then takes police on a high-speed chase where he finally gets killed. Then it is revealed that the bank robber had an extensive criminal history. Oh, it was a male. “you weren’t being sexist“, he writes, “you were playing the odds.” Most men aren’t violent, but most violent individuals are men. Stewart-Williams then discusses a recent article published by The New York Times titled It’s Dangerous to Be a Boy, with the headline (emphasis mine) “They smoke more, fight more and are far more likely to die young than girls. But their tendency to violence isn’t innate.” I will discuss the use of the term “innate” further down.

Stewart-Williams then states, going off the headline quoted above, that the statement means that “sex differences in aggression come entirely from the environment: from culture rather than biology, nurture rather than nature.” Nevermind the false dichotomy here, let’s finish up discussing the gist of the article before getting onto what’s wrong with it. He then states that biology matters as well, and that the claim that male violence isn’t “innate” is the “Nurture Only” position, while we know that “Biology matters as well.” This seems to be the strawman that all evolutionary psychologists battle with: Anyone who disagrees with EP claim C is a “blank slatist” (this phrase taken care of by Robert Richardson in Evolutionary Psychology as Maladapted Psychology); but due to the interaction of nature and nurture, genes and environment, you can’t partition them into percentages—as is done with heritability estimates (see Moore and Shenk, 2016).

So these sex differences in aggression are noticed in all cultures. What could explain this? Stewart-Williams then discusses the Eagly and Woods’ (2016) social role theory of sex differences. They agree—of course—that there are sex differences in aggression and crime found throughout all cultures on earth, but the cause of domination is due to the effect of evolved differences in body size—men being bigger, stronger, and faster than women while women are smaller, weaker, and slower than men. So this proposed hypothesis states that the psychological differences found throughout all cultures is due to physical sex differences.

Why wouldn’t natural selection create psychological sex differences as well as physical ones?“, Stewart-Williams writes. Well the answer to this question is that there are no psychophysical laws so psychological traits/mental abilities can’t be selected. Then there is the fact that natural selection is not an explanatory mechanism since it cannot explain trait fixation because there are no laws of selection for trait fixation (Fodor, 2008; Fodor and Piatteli-Palmarini, 2010).

Stewart-Williams writes “Some argue that, even if culture doesn’t create the aggression sex difference out of nothing, it does still amplify a relatively trivial inborn difference.” This is ridiculous: “culture doesn’t create the sex difference out of nothing”, however, small differences between males and females can be magnified by culture (Eliot, 2009). Note that this is a developmental perspective, and that developmental systems theory (DST) is completely at-ends with Evolutionary Psychology.

Stewart-Williams writes:

Is it just a coincidence that this alleged surge in socialization comes at the same time as the massive surge in circulating testosterone that accompanies puberty in males?

I see he is implying that circulating testosterone levels explain differences in aggression between males and females and that this also explains aggression as well. Though, as I have documented, the claim is false.

Stewart-Williams than writes:

The socialization hypothesis offers no particular reason to expect this. But the decline in violence coincides almost perfectly with the decline in testosterone found in men throughout the adult years, and mirrors the decline found in males of other species. Once again, this is much easier to explain in evolutionary than in sociocultural terms.

How interesting to bring this up. I’m sure most have heard the claim that testosterone levels begin to decrease at around age 25-30 (a decrease in total T of 1-2 percent per year after age 30). Though, note that age-range. What major life events occur during that time for most men? Marriage, children (some bouts of depression). Smoking, too, explains some of it. Shi et al (2013) write:

The annual decline in T (−0.8% per year) is similar to that reported from longitudinal cohort studies in the United States (17), Denmark (36), and Australia (16). The current study strongly suggests that the decline in T is not an inevitable part of aging, which is consistent with a recent cross-sectional study of 325 men 40 years and older self-reporting very good or excellent health (37). Our data show that variability in the change in T is largely explained by smoking behavior and intercurrent changes in health status, particularly obesity, depression, the overall burden of chronic disease, and marital status.

Though, predominantly, the biggest culprit to decreasing testosterone is obesity. Further, smokers have higher levels of testosterone than non-smokers (Wang et al, 2013). This is because smoking cessation causes fat mass to accumulate, and higher fat mass is associated with lower testosterone levels.

In any case, Stewart-Williams continues to talk about the “Nurture Only” (“blank slate”) position. He discusses how human males commit around 95 percent of crime while being 79 percent of homicide victims. He then states that male chimpanzees commit 92 percent of “chimpicides” while male chimps are 72 percent of those who are killed. So if he will use chimps as an example for an “innate” tendency, then I’ll use something on chimps to prove the point that it’s not testosterone that causes aggression, as Stewart-Williams is implying.

In The Trouble with Testosterone, Sapolsky (1997) discusses five chimpanzees. The chimpanzees were then allowed to form a hierarchy, 1-5. Number 3 pushed his weight around on numbers 4 and 5 but was subservient to  numbers 1 and 2. Number three was taken and then injected with testosterone. He then began engaging in more aggressive behavior, which would confirm the hypothesis that testosterone causes aggression, right? Wrong. Sapolsky (1997) writes:

So even though small fluctuations in the levels of the hormone don’t seem to matter much, testosterone still causes aggression. But that would be wrong. Check out number 3 more closely. Is he now raining aggression and terror on any and all in the group, frothing in an androgenic glaze of indiscriminate violence. Not at all. He’s still judiciously kowtowing to numbers 1 and 2 but has simply become a total bastard to number 4 and 5. This is critical: testosterone isn’t causing aggression, it’s exaggerating the aggression that’s already there.

Now let’s get to the problem with the term “innate”: It’s an empty term. It’s a term that people use when they don’t want to think about the development of the trait in question. For example, the term “innate” is thought by numerous researchers today to be driven “by” genes. It is assumed that “innate traits” are “non-malleable.” Maybe the assumption is that only genes are needed for the culmination of trait X. Or maybe the assumption is that a trait is “innate” iff it is fully genetically influenced. Though, there is a problem there, too. What does it mean for something to be “genetically influenced”? What a priori justification exists to privilege genes over any other developmental variables? There is none. Noble’s (2012; 2017) argument rears its head whenever the discussion of “genetic traits” comes up: it’s nonsensical to talk about, since, in a multi-level complex biological system, pinpointing one level is useless since they all interact.

However, Bateson and Mameli (2007) dispense with the term “innate”. They write that “Over-used metaphors from engineering such as ‘‘hardwiring’’ and ‘‘pre-programming’’ applied globally to the outcome of development fail to capture the character of the processes and once again invite the mistaken view that they can be contrasted with their opposites. We believe that a thorough investigation of developmental processes has been hindered by indiscriminate use of the labels ‘‘innate’’ and ‘‘acquired.’’

Sachser, Kaiser, and Hennessey (2013) argue that behavioral profiles are shaped by during the prenatal phase, through adolescence, which adheres to the DST view. Blumberg (2016) writes:

So the next time you see a marvelous and complex behavior—such as a border collie herding sheep or birds flying south for the winter—try to resist the temptation to label it as instinctivehardwiredgenetic, or innate. By foregoing a label and digging deeper, you will open yourself to consideration of the myriad of factors that shape who we are and why we behave the way we do.

In sum, Stewart-Williams does not understand endocrinology (positing evolutionary explanations for T decreases at around the mid-20s in comparison to socio-cultural ones); he does not understand that socialization in male and female babies makes small gaps wider (Eliot, 2009); he does not understand (though he only implied this and did not outright claim it) that testosterone does not cause violence/aggression/crime. Evolutionary Psychologists really need to get a clue. Positing evolutionary explanations (i.e., just-so stories when they cannot be independently verified of the data they purport to explain) does not lend itself to any kind of explanation for why a certain trait persists in the modern world. Lastly (though he did not make the claim here), the terms “innate” and “genetic” are baseless and empty and do not give us any new information about the trait in question.



  1. Samu says:

    Now, I am not in anyway an expert in biology but this quote “it’s nonsensical to talk about, since, in a multi-level complex biological system, pinpointing one level is useless since they all interact” reminds me too much of the irreducible complexity argument made by creationists.


  2. thereallolah says:

    If mental abilities can’t be selected for, then how can testosterone influence the aggression in chimps? Sure it doesn’t cause it but it does exaggerate it. If mental abilities can be exaggerated by testosterone, then mental abilities are influenced by the real world. The “there are no psycho physical laws” approach is in direct contrast to the “testosterone effects are context dependent” one with the chimps. Mental abilities and traits are thus influenced by biology and can be selected like anything else to the degree that they are influenced (abstract concepts can’t be but the thing that produces them can – look at the effects of different types damage to the brain on personality, cognition etc). Indeed Sapolsky actually explains what else has to be happening in the brain for aggression to occur two paragraphs after the one you quoted and indeed, you summarise this in your testosterone article.

    Aggression decline at age 30 could also be explained by the stuff Archer talks about as well with sexual selection (indeed discussing T levels and declining aggression if pointless if T doesn’t have any effect on aggression) – I think SSW is right in that socialisation doesn’t explain this well (to be fair marriage could cause a decline in aggression but it’s not clear why aggressive men wouldn’t just become aggressive, abusive husbands if they’ve been taught all their life to use violence. As far as I can tell this is a problem in cultures with high levels of violence, husbands act abusively towards wives and kids. To be fair marriage does reduce crime rates I think). This would obviously suggest interactionism, which to be fair SSW doesn’t ignore (he notes, after all, that violence and warfare have declined) and his argument is that nurture alone doesn’t explain aggression (and most men aren’t that aggressive anyway, at least not on individual interactions anyway e.g most murderers are men but most men aren’t murderers).


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