The concept of hereditarianism has been a topic of intense debate for decades. Ever since Francis Galton’s inquiries into what makes “genius”, to the advent of twin studies in the 1920s, hereditarian ideas have been espoused in the literature as having explanatory power. Hereditarianism is the theory that genes cause and influence psychological traits and differences in them between people and even groups.
The main claim is that genetics is the main influence and cause of psychological traits like IQ/intelligence. Hereditarians claim that intelligence is greater than 0 percent genetically caused (Warne, 2021) or that a “substantial proportion (20% or more) of differences in psychological traits within and among human populations is caused by genes” (Winegard, Winegard, and Anomaly, 2020). So hereditarianism is true if intelligence is greater than 0 percent genetically caused or if 20 percent of more of the differences in psychological traits are genetically caused. However, the concepts of mind-body dualism (MBD) and developmental systems theory (DST) offer a very powerful challenge to this kind of genetic reductionism/determinism.
MBD is the philosophical theory that the mind and the body are distinct entities. Basically, the mental is irreducible to the physical. If the mental is irreducible to the physical, then the mental can’t be explained in physical terms. Facts about the mind can’t be stated using a physical vocabulary and the mind can’t be described in material terms using words that only refer to material properties. This refutes psychological genetic reductionism; it is impossible for human psychology to be genetically caused/influenced and so this holds for differences between groups and individuals as well.
Developmental systems theory (DST) further establishes that since human development is dynamic and interactive, then genes, environment, behavior and other developmental resources all interact to form the phenotype and shape development. Thus, DST refutes the view, too, that genes cause the development of traits and of the organism as a whole. The hereditarian programme is inherently reductionist, and it attempts to reduce human life and it’s particularities to genes and biology.
The possibility that hereditarianism could reinforce social inequalities is high. From Jensen to Murray and Herrnstein, it has been stated for decades that we need to do something about the lower classes and their having children. Hereditarianism basically would then be removing undesirable people from society based on the false premise that genes have anything to do with their psychology or the undesirable social traits they have.
Hereditarians claim that their research is objective, that they are merely interested in the search for truth. Modern hereditarian thinking can be traced back to Francis Galton. The presupposition that human psychology can be quantitative has its origins with Francis Galton and is directly derived from his eugenic ideas (Michell, 2021). So hereditarian ideas and eugenics are inherently linked. It is the case that genetic determinist ideas like hereditarianism deflect away from actionable positions that could reduce disease far more than eugenic proposals (Holtzman, 1998).
Hereditarianism could be used as justification to accept current existing inequities and inequalities. For if these differences between people are inborn and the result of their genes, then there would be some harsh realities that we as a society would need to accept. People are of course genetically different and these genetic differences then somehow cause group (class) and individual differences. However, contra Murray (2020), social class differences do not lie in the genes and genetics can’t be used as justification to maintain a ruling class, limiting a group’s ability to have children, and minimize social safety nets (Holtzman, 2002).
Why is hereditarianism alluring?
I think it’s simple—it gives us quite simplistic answers on the nature of group, individual, and societal differences. If differences within and between these things reduce to genes, then we can say that the causes are due to genes and they thusly have certain consequences attached to them. This, again, shows how eugenic and hereditarian ideas are married to each other.
It is alluring because it is simplistic and reductionist, deterministic. It posits that differences within and between individuals, groups, and societies come down to genes. Of course individuals, groups, and societies have different gene frequencies—that is the correlation. But the folly is to assume that the genetic differences between them drive the trait (used loosely) differences between them. That is something that has yet to be explained—there is no mechanism of action.
The genetic determinism that is steeped into society also plays a role. If genes largely determine one’s intelligence, then it provides predictability and stability. It suggests a fixed level of ability that simply isn’t malleable due to how genes are thought to work by the hereditarian. This then offers a level of understanding to the hereditarian—the causes of ability and differences in them between people, groups, and societies are due to genetic differences between them, even if we don’t know exactly how these differences manifest themselves genetically. This is why they have to use twin, family, and adoption studies along with GWASs and PGS. This lends them the deterministic tilt they need in order to show that society is stratified due to the genetic differences between groups and individuals.
This assumption, though, is quite clearly false since societies are genetically stratified (the fact that needs to be explained, which the hereditarian tries to argue are due to genetic differences), social stratification maintains this genetic stratification, social stratification causes cognitive stratification, and tests reflect priori cognitive stratification. Thus, the structure of society bakes-in these stratifications, giving the illusion of genetic differences being the causes of differences between people (Richardson, 2017, 2021).
Genetic determinism and reductionism then lead to a kind of “gene worship.” For if differences are mainly due to genes, then the gene is powerful, powerful enough to be causal in the sense that genes dictate certain outcomes that would then manifest in social life and then dictate the course of a society or group of people.
How do MBD and DST combine to refute hereditarian ideas?
MBD and DST combine to refute hereditarianism quite easily. Hereditarianism has two main assumptions:
A1: Genes are the main determinate of differenced in traits and of psychological differences.
A2: Genes and environment can be teased apart using certain methods which shows the proportion of influence each has on a trait.
Assumption 1: This assumption is easily dispatched due to the irreducibility of the mental. Accepting the irreducibility of the mental undermines the hereditarian assumption that genes can account for most of the variation in IQ and other psychological traits. Hereditarianism is a physicalist theory and so relies on the assumption that the mental can be reduced to the physical, whether it be genes, brain physiology or the brain itself. But if the mental is irreducible (and it is), then the hereditarian programme becomes highly questionable and thusly outright false, since no hereditarian has articulated a specified measured object, object of measurement and measurement unit for any psychological trait, IQ included. Since hereditarianism seeks to reduce psychology to genes, then the irreducibility of the mental challenges that assumption, and it ensures that a hereditarian psychology just isn’t possible. So of the mental is irreducible, then it implies that the hereditarian hypothesis is false, since psychology can’t be explained by the physical since it is immaterial. So attempting to explain and measure psychological traits based on genetic assumptions is bound to fail. And there is also the measurement and quantification issue—the irreducibility of the mental challenges the claim that psychology can be measured and quantitative since it isn’t physical.
Assumption 2: Ever since Susan Oyama published The Ontogeny of Information in 1985, simplistic and reductive accounts of genetics and the nature traits have been called into question based on an interactive view of developmental resources. Hereditarians privilege genetic factors above other developmental resources, as if they are special resources. But unlike hereditarian theories, DST proponents argue against any a priori privileging of any developmental resources. So this suggests that genetic factors lack superiority—either inherent or predetermined—over other developmental resources. Genes are on par with other developmental resources (called the causal parity thesis, CPT), and so, this hereditarian assumption is also false.
Thus the combination of MBD and DST combined to refute the simplistic assumptions of the hereditarian. Both combined challenge the reductive and deterministic assumptions of hereditarianism. They do this by calling into question the measurability of psychological traits while advocating for a holistic, non-reductionist perspective which acknowledges the irreducible interplay between all developmental resources.
The arguments against hereditarianism from MBD and DST
Now that I have described hereditarianism and what it sets out to do, along with how MBD and DST refute hereditarianism, I will provide two arguments. The first will conclude that genes aren’t special nor privileged developmental resources. The second will then combine both arguments from MBD and DST to successfully show that the hereditarian dream is a logical impossibility.
P1: If genes are special or privileged developmental resources, then they possess a unique or superior causal role in shaping development compared to other factors.
P2: If causal parity exists, then no developmental resource possesses a unique or superior causal role in shaping development.
P3: If genes do not possess a unique or superior causal role in shaping development, then they are not special or privileged developmental resources.
P4: Casual parity exists.
C: Thus, genes are not special or privileged developmental resources.
Premise 1: This premise asserts that if genes are special, then they must have a distinct role—compared to other resources—in explaining and shaping development. Genes would need to show a unique influence in shaping developmental outcomes. This is a main assumption of hereditarianism and perhaps the most important one, because if the assumption is false then hereditarianism cannot possibly be true.
Premise 2: However, since DNA sequences (genes) do nothing on their own until activated by and for the physiological system, then we can safely state that no single resource would be over and above another in doing any explaining. Development is interactive, rather than individual; these resources work together rather than in isolation.
Premise 3: This premise builds on the idea that if genes lack a superior, or unique causal role in shaping development, then they cannot be privileged or special resources. The absence of exclusive causal influence diminishes—and outright refutes—the claim that genes are special or unique developmental resources with a privileged role in development.
Premise 4: This premise is derived from DST literature, where development is understood as a complex and multifaceted event, influenced by many interactive and irreducible factors. It highlights a need for a holistic, rather than reductionist approach to understanding development.
Conclusion: This conclusion is derived from the claim that if causal parity exists (P4), then no developmental resource possesses a unique or superior causal role, so genes can’t considered special or privileged when it comes to development. P2 emphasizes the equal importance of the interacting of developmental resources, which challenges the claim that any of those resources can be isolated as a causal, privileged factor. P3 challenges the assumption that genes can alone determine how traits develop which then reinforces the interactivity between the resources. P4 then asserts that causal parity exists, and so no developmental resource, including genes, should be privileged. This directly refutes a sometimes unstated assumption of hereditarianism.
P1: If hereditarianism is true, then mental abilities can be explained by genetic factors and can be accurately measured. (Assumption of hereditarianism)
P2: If mental abilities are irreducible to the physical, then they cannot be explained by genetic factors. (From MBD)
P3: If no developmental resource is privileged in biological systems, then genetic factors alone cannot determine any trait, including psychological traits. (From DST)
C1: If mental abilities are irreducible to the physical, then hereditarianism is false. (Modus tollens, P2)
C2: If no developmental resource is privileged in biological systems, then hereditarianism is false. (Hypothetical syllogism, C1, P3)
Premise 1: This is an accepted and accurate depiction of hereditarianism and is how hereditarianism is understood in the literature.
Premise 2: This draws on MBD and the irreducibility of the mental. I have been using dualistic arguments for years to argue against the concept of hereditarianism. Mental abilities cannot be reduced to anything physical, and therefore refutes the main assumption of hereditarianism, that genes can determine psychological traits and differences in them between people, groups and societies.
Premise 3: This is derived from DST. Any kind of development is due to the interactive and irreducible nature of development. It asserts that there is no privileged level of causation between resources, which then refutes the claim that genes should be looked at to explain any differences—any that we deem “good and bad”—between people.
Conclusion 1: This conclusion follows using modus tollens. If the consequent in the conditional statement in P1 is false (“If mental abilities are irreducible to the physical”), then the antecedent (“hereditarianism”) must also be false. If mental abilities cannot be explained by genetic factors (asserted in P2), then it contradicts the main assumption of hereditarianism (P1). Therefore if mental abilities are irreducible to the physical, then hereditarianism is false.
Conclusion 2: If mental abilities are irreducible to the physical (C1), and no developmental resource is privileged in biological systems (P3), then it follows that hereditarianism is false. This conclusion stems from the entailment of hereditarianism which relies on privileging genetic factors over and above other factors. But if no developmental resource holds privilege, then hereditarianism is false, since it quite clearly assumes the superiority of genes in trait determination. Thus the conclusion challenges hereditarianism based on the premise that no developmental resource is privileged, and since hereditarians privilege genes, then hereditarianism is false.
The two main assumptions of hereditarianism quite clearly do not hold when inspected using a MBD and DST lense. Thus, since hereditarianism is false, then believing it to be true would be socially destructive. And these socially destructive policies were an outcome of the IQ test then they were brought to America, using the assumption that genes were the primary cause for differences in IQ scores. Here’s the argument:
P1: If hereditarianism is false, then it does not accurately represent the complex nature of human traits and abilities.
P2: If we believe in a false representation of human traits and abilities, then it can lead to discriniminatory practices and unjust societal outcomes.
P3:, Hereditarianism is false.
C: Thus, if we believe hereditarianism to be true when it is false, then it can lead to socially destructive outcomes.
This is why I have argued that IQ tests should be banned. Nevertheless, hereditarianism and along with it IQism are proven false, using conceptual arguments. The dissimilarity between psychological traits and physical objects shows that psychology can’t be measured, so there can’t be a science of the mind. For these reasons, hereditarian ideas should be directly discounted and ignored, since their assumptions are clearly false.
“Mental abilities cannot be reduced to anything physical”
For an incisive demonstration of such reducibility, see Valentino Braitenberg’s “Vehicles: Experiments in Synthetic Psychology”: