A recent study conducted by evolutionary psychologists, David Buss and William von Hippel, has found empirical support for the claim that evolutionary psychology is a controversial field among social psychologists.1 Their study titled, “Psychological Barriers to Evolutionary Psychology: Ideological Bias and Coalitional Adaptations,” posed questions to social psychologists to assess their political orientation and their attitudes towards evolutionary psychology, specifically, the extent to which evolutionary theory applies to humans. The responses of the social psychologists to the question of whether Darwinian evolution applies to human minds were highly variable despite being in near unanimous agreement that Darwinian evolution is not only true, but also applies to physical human traits.

Further questions revealed that their discomfort with the notion of evolved minds was neither due to religious beliefs nor to beliefs in human specialness, but were due to their varying opinions on “hot button variables” in evolutionary psychology. These included topics such as genetic tendencies for violence, universal standards of beauty, and psychological sex differences. In other words, evolutionary theory becomes contentious when it veers away from the human body to the human mind.

In his article for Quillette, Colin Wright wrote that evolutionary theory is and always has been controversial among the general public, but not to scientists. However, the branch of evolutionary theory that has proved most controversial to scientists is evolutionary psychology.

While evolutionary psychology may be controversial among social psychologists, evolutionary theory in general is one of the most well-substantiated theories in all of science. Only evolutionary theory can explain the organized complexity of life in contrast to simple, nonliving matter. Scientists unanimously agree that the intricately designed human eye is an adapted organ, one that arose not by chance, but through the gradual process of natural selection. However, many fail to expand this argument to the far more complex organ of which the eye is an extension, and into which the eye carries all its information, the human brain. This is especially concerning given that scientists almost exclusively invoke evolutionary theory in order to understand the mental processes and behavioral patterns of all other animals.

While Buss and Hippel’s study only found some empirical support for their hypotheses about ideology and evolutionary psychology, since its inception, the field has unfairly received an unfair amount of criticism. Since the field has existed, evolutionary psychology, then referred to as “sociobiology,” has received enormous pushback from academics. It came under fiery criticism in a letter written in the 1970s titled, “Against ‘Sociobiology,’” which was signed by a number of prominent scientists such as Richard Lewontin and Stephen Jay Gould who were particularly hostile to the field. This letter sparked a big debate in the scientific community of the relevance of evolutionary analyses on human psychology. The chain of pushback against the findings of evolutionary psychology has continued right up into the present day especially when it comes to psychological differences between the sexes.

Recently, psychologist Michael Reichert, wrote an opinion piece for the New York Times suggesting that boy’s “tendency towards violence isn’t innate.” He writes, “Boys don’t come into the world with some inborn tendency toward domination or violence” rather, “violence springs from what boys learn about what it means to be a man.”

Seventeen years after I wrote The Blank Slate, the dogma remains strong: NYT op-ed claims boys are socialized to be rougher than girls, despite cross-cultural universality, presence in other species, sensitivity to prenatal testosterone, adult punishment.. https://t.co/LmEqFDYg5R — Steven Pinker (@sapinker) March 31, 2019

Additionally, the notion that there are sex differences in brain structure has also been coming under fire. A recent article in the Guardian refers to comments made about sex differences in brains by neuroscientist Gina Rippon. The article says, “Are there any significant differences based on sex alone? The answer, she says, is no. To suggest otherwise is ‘neurofoolishness.’”

I imagine the journalist has misunderstood, here, because no scientist would make a claim as risible as this. https://t.co/bYrM5SjLA3 pic.twitter.com/klOHsMIhO8 — Stuart Ritchie (@StuartJRitchie) February 24, 2019

However, the idea that there are sex differences in brains is well-established in the scientific literature. Indeed, it has recently been corroborated by a large-scale study published in Nature that found sex differences in gray matter volume in many regions of the adult brain.2 Moreover, a recent study published in Developmental Cognitive Neuroscience found evidence for sex differences in brain functional connectivity in utero and therefore presumably before socialization could possibly have been at play.3

Additionally, Rippon’s comments in this article have been criticized by Debra Soh an expert in human sexuality and Larry Cahill an expert in neurobiology. Cahill compares the headline of a positive review of Dr. Rippon’s recent book published in Nature, “Neurosexism: the myth that men and women have different brains” to the headline, “The myth that evolution applies to humans.” Both are equally absurd. Cahill writes:

What exactly are people like Rippon so afraid of? She cites potential misuse of the findings for sexist ends, which has surface plausibility. But by that logic we should also stop studying, for example, genetics. The potential to misuse new knowledge has been around since we discovered fire and invented the wheel. It is not a valid argument for remaining ignorant.

Additionally, the types of arguments made by Rippon among others, falsely conflate equality with sameness. They presume that our moral commitment to equal treatment of the sexes is dependent on there being no differences between the sexes. Cognitive psychologist Steven Pinker put it best: “Equality is not the empirical claim that all groups of humans are interchangeable; it is the moral principle that individuals should not be judged or constrained by the average properties of their group.”4 What Soh and Cahill are criticizing is a forced misuse of scientific data in light of political concerns. Instead of dispassionately inquiring into scientific questions, facts from politically controversial research are being distorted out of concern for how the data might be used by the worst among us. And today most of the distortion of the science of human nature is coming from the extreme political Left.

While all ideologies come with their own prepackaged presumptions that can contaminate dispassionate scientific inquiry, the reason why I’m focusing on the political left in this article is because their view is predominant in academia. Those on the right once were the main enemies of evolutionary theory, but today, as Colin Wright argues, those on the extreme left are the “new evolution deniers.”

But perhaps I’m dismissing perfectly sensible concerns. After all, don’t evolutionary psychologists believe that we are predestined towards violence since it is in our genes? That our worst behaviors are hardwired, and therefore cannot be changed? Moreover, doesn’t evolutionary psychology justify social injustices and inequalities by arguing that different people have different biological natures? Isn’t evolutionary psychology just social Darwinism in a new garb, fitted with the veiled accessories of eugenics, and bigotry?

Not at all. Most of these arguments stem from misconceptions of the field, namely, believing that evolutionary psychologists are committing the naturalistic fallacy, conflating proximate with ultimate explanations, and attempting to make everything into an adaptation. Most importantly, these misconceptions stem from conflating what’s empirically true with what ought to be true. For instance, taking the point of view of an evolutionary psychologist to whom he is opposed, Gould writes:

Perhaps the most popular of all explanations for our genocidal capacity cites evolutionary biology as an unfortunate source — and as an ultimate escape from full moral responsibility … but we cannot be blamed for these moral failings. Our accursed genes have made us creatures of the night.5

But what evolutionary psychologist is Gould imagining that would take evolutionary theory as an invitation to escape moral responsibility for committing a crime? It must have been one made of straw.

I believe that most of the resistance to evolutionary psychology both then and now stems from two fallacies: (1) that the nasty aspects of our human nature, such as tendencies for violence, are natural and therefore, good. This is known as the naturalistic fallacy; and (2) that an evolved human nature necessarily implies genetic determinism and inflexibility, both of which are found in the above quote.

First, it’s important to realize that what is adaptive has nothing to do with human notions of goodness or morality, a common misconception of evolution. Like gravity or the laws of thermodynamics, natural selection proceeds without regard for human morals, increasing the frequency of those genes that lead to higher reproductive fitness in individuals that have them. A description of human nature is in no way a prescription for how we ought to be. To deduce the latter from the former is to commit a logical error that jumps from saying, for example, homicidal tendencies are at least partly an adaptation to saying that homicidal tendencies are good and should be encouraged. If homicidal tendencies were adaptive, that would be something interesting and worth understanding, but would say nothing about how we ought to be. No matter the evidence about human nature, whether tendencies towards homicide and rape are in our nature, or whether intelligence is 10 percent or 90 percent heritable, our moral commitments to correcting social injustices, treating people as morally worthy individuals, and facilitating political and economic equality should not waver.

Second, that something is a part of human nature does not necessarily mean it will be expressed. Pioneers of evolutionary psychology, John Tooby and Leda Cosmides, give the example of a callus-forming adaptation that all humans have coded in their genome.6 But simply possessing the gene does not mean everyone will have calluses. This is because callus formation depends on both the genetic blueprint and the environmental determinant for it, namely, friction. If one were to wear gloves in order to prevent friction on their hands, they won’t form calluses. Similarly, many forms of violence likely are consequences of adaptations, which, therefore, have a genetic basis. Fortunately, moral, cultural, and social norms and institutions of the modern world can, as it were, act as the glove that prevents these violent tendencies from being expressed. They can facilitate the expression of better aspects of our human nature like altruism, cooperation, self-control, empathy—the better angels of our nature. A book of that title outlines vast amounts of empirical data arguing just that.7

Scientists like Stephen Jay Gould and Richard Lewontin who have never failed to bristle at the notion that the human mind is a product of Darwinian selection, but are perfectly fine with the notion that the human body is, are fighting a losing battle. They share their ranks with those who claim that vague notions of “socialization,” and “culture” are primarily responsible for traits of the human mind. This has been called the blank slate view of the mind because it is a view of human nature that denies any innate structure to the mind and instead claims that humans are born with a clean slate, awaiting the hand of culture to mold it.8 The reasons why this cannot be the case are numerous. For one, socialization and culture do not exist independently of human minds, a fact one would think is too obvious to have to be stated and yet is commonly forgotten. Human minds are what created culture in the first place. Secondly, it would be virtually impossible for humans to take up and learn their culture and all its complexity without innate mechanisms in place to make it happen, in the same way that acquiring a language is virtually an impossible task for a blank slate that lacks built-in assumptions about the common structure and regularities of languages.

Interestingly, Buss and Hippel’s explanation for the ideological backlash against evolutionary psychology also accounts for the phenomenon that Soh and Cahill are pointing out. In their paper, Buss and Hippel argue that some of the resistance to evolutionary psychology stems from psychological adaptations for maintaining in-group coalitions and punishing competing coalitions. This is done mostly to broadcast one’s commitments to admirable goals such as political and gender equality and social justice, known as virtue signaling. Evolutionary psychologists seem to be going against these admirable goals by researching into such politically and morally sensitive topics as the psychological differences between the sexes. However, again, this is a non sequitur. Our moral commitment to value individuals does not hinge on what the data show.

Far from objectionable, many hypotheses about mind and behavior coming from evolutionary psychology are so obvious that an explanation often seems superfluous. A commonplace example that bears the unmistakable stamp of evolutionary logic is fear. Fear is an emotion with a function, namely to solve a recurrent and important problem posed to humans throughout their evolutionary history: survival. It is an emotion that takes in a limited set of inputs, namely, signs of danger to either oneself or one’s kin, and produces outputs in the form of physiological and behavioral changes that lead to an outcome commensurate with the goal, i.e., avoiding harm.9

The same information-processing, evolutionary logic holds for most other emotions like shame, guilt, anger, and sexual jealousy.10,11,12 They evolved because the genes for those emotions helped their owners survive and reproduce, allowing those genes to prevail among alternatives and therefore replicate into the next generation. In this sense, behaviors, emotions, and other mental faculties can be dissected and understood like a liver, spleen, or a heart, all of which have adaptive functions that were selected among alternative designs through evolutionary time.

However, it’s important to realize that was advantageous in hunter-gatherer societies is often maladaptive in today’s world. For example, it’s easy to see how a preference for sugary foods, which was adaptive in the environment in which humans evolved, is maladaptive in the modern world. Today, sugar is far from rare, but is instead added to everything from drinks to hamburger buns. Nevertheless, “maladaptive” does not mean or imply “irrelevant.” Quite the contrary. Obesity, as opposed to starvation is a significant problem in the developed world. And it is largely a consequence of a mismatch between the environment in which we evolved—where sugar was scarce—and the environment in which we are now—where sugar is plentiful.

Admittedly, humans are different from all other life forms. Humans have culture. And human culture differs widely throughout the world. Undoubtedly, cultural factors influence human mind and behavior. For example, men are more violent than women, committing almost all forms of violent crime more often than women.13,14,15 Perhaps this is a result of socialization into masculine gender roles.16 Parent’s may positively reinforce their sons to be more aggressive and competitive while punishing their daughters when they show the same behaviors. Perhaps throughout their upbringing, boys are encouraged to display their aggression and physical prowess in sports, whereas girls are discouraged from sports and are encouraged into more caring and stereotypically feminine roles. Additionally, media may influence behavior. More often boys play violent video games and watch violent films, which might make them more violent in the long run.17 While sociocultural factors such as these influence mind and behavior to some degree I have to admit, I find these explanations deeply unconvincing.

Firstly, at least just as often as parents encourage their son’s aggressiveness, they punish it. Parents are constantly scolding their sons for misbehaving. Parents and teachers tell young boys again and again to keep their hands to themselves, to stop acting out, to be nicer, and have empathy. The sociocultural stance would somehow have to provide evidence that boys are receiving one message and girls are receiving another consistently enough to cause distinct differences in their mind and behavior. Secondly, why are parents so often scolding their young boys? Because they are rowdier! I expect that many parents would be skeptical of the sociocultural explanation here. Much of parenting consists of parents responding to the very different natures of each of their children, natures that were not reinforced and conditioned into existence by the TV, but that the children were born with.18

It is my contention that sociocultural factors that have been proposed in place of evolutionary factors as causal influences on mind and behavior have been overstated, while the importance of evolutionary factors have been understated. Evolutionary explanations also account for human aggression and they do so by positing a simpler and more likely theory that links human aggression to a broader trend found throughout the animal kingdom in general.

Robert Trivers’s parental investment theory defines parental investment as “any investment by the parent in an individual offspring that increases the offspring’s chance of surviving (and hence reproductive success) at the cost of the parent’s ability to invest in other offspring.”19 In most species there is an asymmetry in the minimum amount of parental investment in offspring between males and females such that females tend to invest more resources, energy, and time into offspring than do males. This asymmetry in minimum parental investment is prevalent in mammals because it’s the females that gestate and lactate, whereas males contribute a morsel of sperm.

Lower parental investment in offspring makes it pay off for males to adopt a quantity-maximizing strategy to sire more offspring since sperm is cheap. And so, they tend to mate with as many females they can, which necessarily forces other males to go mateless leading to intrasexual competition—that is, competition among males for access to females.20

That fierce intrasexual competition in males has characterized the evolutionary history of many animal species is evidence by the evolution of weapon-like phenotypes in males: deer antlers, rhino horns, narwhal tusks, to name a few.21 These weapons are devoted to competing with other males for access to mates. Males in other species, such as the elephant seal, have size and strength differences rather than weapons, that are indicative of a large asymmetry in parental investment in offspring weighted towards the female side.22 Male elephant seals compete for access to female mates which they win by brutal fighting contests governed by the following rule: the bigger, the better. Bigger seals are better fighters, better fighters win fighting contests against males, winning against males leads to multiple mating partners, which leads to more offspring that in turn have inherited their father’s genes for bigger size, and therefore better fighting ability. And so, males have evolved to be at least four times the size of females.23,24

Although sex differences are highly diluted to an unusual degree in humans compared to other mammals because of their unusually large male investment in offspring, parental investment theory predicts that similar sex differences should also be found in humans. While human males do not have horns protruding from their heads, some researchers hypothesize that greater male size, strength (especially upper body strength), muscle mass, bone density, among other physical differences, are indicative of an evolutionary history of male intrasexual competition and hence of greater male aggression and proclivity for violence.25,26,27 Indeed, one study found that the average man is stronger than 99.9 percent of women.28 Nevertheless, the notion that male psychology has adapted alongside physical traits of aggression and violent capabilities has been contested by psychologists advancing sociocultural theories, such as Alice Eagly who downplays the influence of evolutionary factors on human psychology.29,30

However, in my mind, there’s no reason to think that evolutionary processes have been working away at the human body but left human psychology unscathed. I find it extremely unlikely that all the evolutionary selection pressure trends acting on mammals, including our closely related ape relatives, and even including the human body itself would mysteriously stop at the neck. In his recent book, The Ape that Understood the Universe, evolutionary psychologist, Steve Stewart-Williams, offers his insight into this apparent conundrum: “why would natural selection give men the physical equipment needed for violence but not the psychological machinery to operate it? This would make about as much sense as giving us teeth and a digestive system, but not a desire to eat.”31

Additionally, it seems unlikely that in the midst of this unprecedented pause in selection pressure on the human mind, sociocultural factors would swoop in and fashion human psychology exactly in line with what an evolutionary analysis would expect to find. Better to just cut out the middleman entirely and go with the more parsimonious evolutionary explanation.

It’s important to keep in mind, however, that sociocultural and evolutionary explanations are not necessarily at odds with each other. Most often I suspect the two are operating simultaneously in causing most human actions such as aggressive behavior. Problems arise when proximate explanations, like sociocultural theories, are being used in place of ultimate explanations, like evolutionary theories and vice versa to explain human characteristics.

Most of the resistance to evolutionary psychology coming from the left is tribal, as Buss and Hippel explain in their article. But science should be in the business of advancing knowledge of the world and its inhabitants rather than advancing certain groups or sides over others. Like any discipline of science, evolutionary psychology has not been untouched by prejudice and ridiculous theories. But most of them were either unfalsifiable and thus unscientific or were falsifiable and subsequently refuted by experimental tests. Evolutionary psychology, like any other scientific discipline ,progresses by conjecture and refutation. That most of these conjectures will be falsified and refuted is not a sign that the discipline is pseudoscience. Rather, it is a sign that knowledge of the discipline is advancing. Evolutionary psychology is a new field and needs much more progress in order for researchers to be sure of their findings. This is especially true for a field making claims about a universal human nature. A big challenge lies ahead for evolutionary psychologists. It is one that we should earnestly embrace in order to further our understanding of human nature, rather than shy away from in fear of being politically incorrect.



Alex Mackiel is an undergraduate psychology and English double major at Carleton College who will be joining the SUNY New Paltz Evolutionary Psychology Lab for graduate school. You can follow him on Twitter @ajmackiel

References

1 Buss, D.M. & von Hippel, W. (2018). Psychological barriers to evolutionary psychology: Ideological bias and coalitional adaptations. Archives of Scientific Psychology, 6, 148-158.

2 Lotze, M., Domin, M., Gerlack, F.H., Gaser, C., Lueders, E., Schimidt, C.O., & Neumann, N. (2018). Novel findings from 2,838 adult brains on sex differences in gray matter brain volume. Scientific Reports, 9, 1-7.

3 Wheelock, M.D., Hect, J.L., Hernandez-Andrade, E., Hassan, S.S., Romero, R., Eggebrecht, A.T., & Thomason, M.E. (2019). Sex differences in functional connectivity during fetal brain development. Developmental Cognitive Neuroscience, 36, 1-10.

4 Pinker, S. (2002). The Blank Slate: The modern denial of human nature. New York, NY: Viking.

5 Gould, S.J. 1998. The Diet of Worms and the defenestration of Prague. In Leonardo’s mountain of clams and the Diet of Worms: Essays in natural history. New York: Harmony Books.

6 Tooby, J., & Cosmides, L. “The Theoretical Foundations of Evolutionary Psychology.” The Handbook of Evolutionary Psychology. (2016). Vol 1, 2nd ed. Edited by David Buss.

7 Pinker, S. (2011). The Better Angels of Our Nature: Why violence has declined. New York, NY: Viking.

8 Pinker, S. (2002). The Blank Slate: The modern denial of human nature. New York, NY: Viking.

9 Tooby, J., & Cosmides, L. “The Theoretical Foundations of Evolutionary Psychology.” The Handbook of Evolutionary Psychology. (2016). Vol 1, 2nd ed. Edited by David Buss.

10 Szyncer, D., Tooby, J., Cosmides, L., Porat, R., Shalvi, S., & Halperin, E. (2016). Shame closely tracks the threat of devaluation by others, even across cultures. PNAS, 113, 2625-2630.

11 Robertson, T.E., Sznycer, D., Delton, A.D., Tooby, J., & Cosmides, L. (2018). The true trigger of shame: social devaluation is sufficient, wrongdoing is unnecessary. Evolution and Human Behavior, 39, 566-573.

12 Buss, D.M. (2018). Sexual and emotional infidelity: Evolved gender differences in jealousy prove robust and replicable. Perspectives on Psychological Science, 13, 155-160.

13 Daly, M., & Wilson, M. (1990). Killing the competition: Female/female and male/male homicide. Human Nature, 1, 81-107.

14 Nivette, A., Sutherland, A., Eisner, M., & Murray, J. (2019). Sex differences in adolescent physical aggression: Evidence from sixty-three low-and middle-income countries. Aggression Behavior, 45, 82-92.

15 Wright, J., Beaver, K., & Ellis, L.F. (2009). Handbook of crime correlates. London: Academic Press.

16 Wood, W., & Eagly, A.H. (2012). Biosocial construction of sex differences and similarities in behavior. In J.M. Olson & M.P. Zanna (Eds), Advances in Experimental Social Psychology (pp. 55-123). Burlington, MA: Academic Press

17 Wood, W., & Eagly, A.H. (2012). Biosocial construction of sex differences and similarities in behavior. In J.M. Olson & M.P. Zanna (Eds), Advances in Experimental Social Psychology (pp. 55-123). Burlington, MA: Academic Press

18 Avinum, R., & Knafo, A. (2013). Parenting as a reaction evoked by children’s genotype: A meta-analysis of children-as-twins studies. Personality and Social Psychology Review, 18, 87-102.

19 Trivers, R.L. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man, 1871-1971 (pp. 136–179). Chicago, IL: Aldine.

20 Ibid.

21 Futuyma, D.J., & Kirkpatrick, M. (2017). Evolution (4th ed.). Sunderland, MA: Sinauer Associates.

22 Lindenfors, P., Tullberg, B.S., & Biuw, M. (2002). Phylogenetic analyses of sexual selection and and sexual size dimorphism in pinnipeds. Behavioral Ecology and Sociobiology, 52, 188-193.

23 Ibid.

24 Futuyma, D.J., & Kirkpatrick, M. (2017). Evolution (4th ed.). Sunderland, MA: Sinauer Associates.

25 Lassek, W.D., & Gaulin, S.J.C. (2009). Costs and benefits of fat-free muscle mass in men: relationship to mating success, dietary requirements, and native immunity. Evolution and Human Behavior, 30, 322-328.

26 Puts, D.A. (2010). Beauty and the beast: mechanisms of sexual selection in humans. Evolution and Human Behavior, 31, 157-175.

27 Stoll, T., Huber, E., Seifert, B., Michel, B.A., & Stucki, G. (2000). Maximal isometric muscle strength: Normative values and gender-specific relation to age. Clinical Rheumatology, 19, 105-113.

28 Lassek, W.D., & Gaulin, S.J.C. (2009). Costs and benefits of fat-free muscle mass in men: relationship to mating success, dietary requirements, and native immunity. Evolution and Human Behavior, 30, 322-328.

29 Wood, W., & Eagly, A.H. (2012). Biosocial construction of sex differences and similarities in behavior. In J.M. Olson & M.P. Zanna (Eds), Advances in Experimental Social Psychology (pp. 55-123). Burlington, MA: Academic Press

30 Eagly, A.H., & Steffen, V.J. (1986). Gender and aggressive behavior: A meta-analytic review of the social psychological literature. Psychological Bulletin, 100, 300-330.

31 Stewart-Williams, S. (2018). The ape that understood the universe: How the mind and culture evolve. New York, NY: Cambridge University Press.

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