Six flawed biological theories
What can disproven theories teach us about science and society?
Welcome back to The Science Fictional Now! Last month, we discussed four science fiction novels examining the limits of human rationality and in a way, this post is about those things too.
But the ‘science fiction’ we’ll be discussing today takes the form of obsolete scientific hypotheses rather than chronicles of journeys to far-flung planets. The limits of rationality we’ll encounter have less to do with questions of the universe’s fundamental intelligibility and more to do with specific errors in individual thinking.
Of course, some of these ideas were merely hypotheses that ended up not being supported by experimental data: phenomena that we expect to occur within the bounds of rigorous science. In this case, the word ‘theory’ refers simply to the prediction that was made. But ‘theory’ can also refer to sets of principles thought to govern a given situation, and indeed we’ll encounter theories today that were considered factual to various extents.
I’ve attempted to compile a set of theories that are interesting and contain a variety of characteristics. They’re all broadly within my own field of biology, but implicate different subfields within the discipline (e.g., biochemistry, genetics) or connect it to other fields entirely (e.g., geology and even law). By considering them, we can see science working according to its own norms and being used as a means to other social and political ends. We can see the various ways in which they arose, the ways in which they were (or weren’t) tested, and how they impacted society in their own times. In some cases, we can even see how certain theories persist after being disproven, or how their language is appropriated by new scientific movements.
I’ve structured this post so that the theories can be read in order or independently and provided section markers below. As always, please feel free to leave a comment or reach out to me directly - I’m always excited to talk more about the material in these posts. Enjoy!
Apollo’s theory of reproduction
The first scientific theory we’ll discuss comes from an unlikely place: Ancient Greek tragedy1. In a trilogy of plays titled the Oresteia, the renowned ‘father of tragedy’ Aeschylus chronicled the mythological origin of the Athenian justice system, depicting interactions between the ancients and their Gods to explore the concepts of justice and revenge. The Oresteia opens with the murder of King Agamemnon of Mycenae by his wife Clytemnestra, avenging the earlier sacrifice of their daughter Iphigenia. Clytemnestra’s actions beget a cycle of vengeance, however: in the second play her son Orestes returns from exile, killing Clytemnestra to avenge the death of his father Agamemnon. Thus, in the trilogy’s final play, Orestes must stand trial in Athens for the murder of his mother.
Orestes is defended by the God Apollo, who pleads Orestes’ case by utilizing an unorthodox theory of reproductive biology. Apollo states that the mother is merely a “nurse of the new-planted seed”, with the father alone providing the material that spurs the child’s development. Thus, Apollo contends, Orestes has killed a woman who is no more related to him than a stranger; his duty to avenge his father should override his crime of matricide.
Despite his divine status, Apollo’s theory is at odds with the last century of biological research. We now know that children inherit 23 chromosomes from each parent; in genetic terms mother and father contribute almost2 equally to their offspring. Yet, the Athenian jury deciding Orestes’ fate is unaware of this fact and they accept Apollo’s theory along with his other arguments. He is able to persuade half of the jury that Orestes is innocent. The Goddess Athena, who has been presiding over the trial, steps in to cast the final vote, acquitting Orestes and establishing the trial as the cornerstone of the Athenian criminal justice system. In the theater of the courtroom, flawed science has played a pivotal role.
Feeble-mindedness
As strange and interesting as Apollo’s theory is, we can at least take solace in the fact that its legal influence was confined to a fictional court. Other fallacious theories, however, have exerted legal influence in the real world. And while Apollo marshaled his theory as evidence within a trial, other erroneous theories have been the chief ingredients of laws themselves.
One such example comes from the eugenics movement, which sought to improve the ‘quality’ of humanity using insights from genetics. The term ‘eugenics’ was coined by the geneticist Francis Galton in 1883 and by the early decades of the 20th century was considered a bona-fide science. During this time, eugenics was backed by important institutions, boasted a slate of dedicated organizations, conferences, and journals accordingly. Its influence even extended into the mainstream: eugenics served as the basis for the notorious Fitter Family Contests and a number of forced sterilization laws in the United States. A total of 33 states passed such laws over the first two thirds of the 20th century, leading to the sterilization of over 60,000 individuals.
One such statute was upheld in the landmark Supreme Court case Buck v. Bell (1927); the ruling allowed the sterilization of a Virginian woman named Carrie Buck to proceed and has never been definitely overruled by the Court. Buck had already lived a difficult life, growing up in an foster family after her mother was diagnosed as ‘feeble-minded’ and committed to an institution. She became a victim of rape and ultimately met the same fate as her mother as her foster family tried to save face. The trait of feeble-mindedness has become a prominent example of the less-than-rigorous science that served as the basis for eugenics, but in 1927 the legitimacy of Buck’s diagnosis and the underlying theory were crucial to the court’s ruling. The court saw forced sterilization as a way to remove feeble-minded people from the gene pool and ostensibly prevent their children from further taxing society.
Psychologist Henry Goddard was likely the individual who did the most to establish feeble-mindedness as a phenotype of eugenic interest in the 1910s. He created IQ test-based standards for the diagnosis of mental disability and undertook large-scale familial studies which he claimed demonstrated that feeble-mindedness was controlled by a single recessive gene. Of course, no one has ever discovered this gene; intelligence is in fact a complex trait controlled by many genes and environmental factors, unlikely to be inherited in any manner detectable by one of Goddard’s family studies.
Not to be outdone, the zoologist Charles Davenport described a more humorous but only slightly less notorious trait that he called “love of the sea” and claimed was inherited in a Mendelian manner. Davenport wrote that “It is theoretically possible that some mothers are heterozygous for love of the sea, so that when married to a thalassophilic man half of their children will show sea-lust and half will not.” The reductionist view of genetics held by Goddard and Davenport was typical of eugenicists and belied the general lack of precision in eugenics.
Even in its heyday, though, eugenics was already drawing spirited criticism from prominent scientists. In 1925, for instance, the geneticist Thomas Hunt Morgan offered a grim appraisal of feeble-mindedness, writing that:
“The case most often quoted is feeble-mindedness that has been said to be inherited as a Mendelian recessive, but until some more satisfactory definition can be given as to where feeble-mindedness begins and ends, and until it has been determined how many and what internal physical defects may produce a general condition of this sort, and until it has been determined to what extent feeble-mindedness is due to syphilis, it is extravagant to pretend to claim there is a single Mendelian factor for this condition”
Morgan’s own seminal work with the fruit fly Drosophila melanogaster was crucial in elucidating the relationship between genetics and developmental biology, often showcasing the sophisticated mechanisms underlying the inheritance of even simple traits. Eugenicists sought to explain everything through genetics, but ultimately advances in that very field helped discredit their theories so thoroughly.
While traits like feeble-mindedness have been branded unscientific and forced sterilization laws have largely disappeared3, some of eugenics’ core questions have persisted into the 21st century. For example, the school of thought commonly called ‘new eugenics’ or ‘liberal eugenics’ advocates the use of novel biotechnologies - such as genome editing technology and pre-implantation genetic diagnosis - to select genes that might prevent suffering or even enhance human capabilities. Wary of eugenics’ dark past, new eugenicists argue against state interference in the gene pool, advocating instead for selection at the level of individual or parental choice. We’ve previously discussed the complicated ethics of human enhancement, and new eugenics has unsurprisingly been met with its fair share of criticism. But beyond the thorny debates it provokes, the reclamation of eugenics provides us with an interesting case study in how the social and political dimensions of a theory can be affected by or stand independent from scientific evidence. As we’ll see, theories survive and re-emerge in a variety of ways, and not always with such an awareness of the past.
Heritable plant vernalization
While eugenics might be the most famous misuse of genetics in the early 20th century, it’s likely not even the most destructive. That dubious distinction almost certainly belongs Lysenkoism, the set of agricultural theories and practices that prolonged and worsened famines in the Soviet Union which killed millions. Trofim Lysenko, from whom Lysenkoism took its name4, was born to a peasant family in present-day Ukraine but rose to become the central figure in Soviet biology by the late 1930s.
Lysenkoism was comprised of a set of unconventional ideas about genetics and a corresponding array of agricultural practices that Lysenko claimed would increase crop yields. Lysenko dismissed Mendelian genetics, instead basing his theories on the Lamarckian idea that traits developed during a parent’s lifetime can be passed on to offspring. Lysenko claimed that environments, and not genes, were the arbiters of trait development. Accordingly, his theory of plant development posited that plants moved through several discrete stages of life, only progressing to the next one when certain conditions were met.
Among Lysenko’s favored techniques was vernalization, the practice of exposing seeds typically planted in winter to cold temperatures, thus allowing them to be planted in spring with shortened growth times. Lysenko believed that the technique was both broadly applicable and heritable and brought it into wide use in Soviet agriculture accordingly. While more recent research has shown that vernalization does occur in some plant species, Lysenko grossly over-applied his poorly-tested theory, drastically increasing the number of vernalized seeds used in Soviet agriculture. Ultimately though, Lysenko’s methods failed to raise Soviet crop yields as he had predicted, leading him to inflate reported food production numbers to save face.
Lysenko’s doctrine stemmed in large part from his desire to mold science such that it fit with the Marxist-Leninist ideology espoused by Stalin. His obsession with the influence of the environment mirrored the dialectical materialism privileged by Marxism and his obsession with heritability likely reflected the idea that society could be improved through heritable changes in attitude among citizens. Lysenko dismissed Mendelian genetics as a pseudoscientific invention of the bourgeoise and wrote that “any science is based on class” - a notion that even Stalin found extreme.
This did little to stop Lysenko’s rise Stalin-era Soviet scientific establishment, however. Soviet agricultural policy had yielded disastrous results in the early 1930s and Lysenko was a member of the proletariat with politically correct theories and radical new methods, making him an ideal candidate for elevation. Lysenko became president of the Lenin Academy of Agricultural Sciences in 1938 and continued to consolidate his power throughout the remainder of Stalin’s reign. But Lysenko ultimately failed to deliver on his promises, actively contributing to subsequent famines and pushing out scientists who continued to study Mendelian genetics, damaging Soviet science for decades to come.
Many of Lysenko’s theories were at odds with the work of pioneering American scientists such as Thomas Hunt Morgan, receiving criticism even within the Soviet Union. Criticism of Lysenkoism intensified in the late 1940s, with western commentators frequently identifying his doctrines as key manifestations of pseudoscience. Lysenko’s political influence within the USSR diminished under Nikita Khrushchev and disappeared entirely under subsequent leaders; more conventional agricultural practices were adopted to correct Lysenko’s failure to increase Soviet crop yields.
Even as mainstream genetics has once again become mainstream in the Soviet Union, however, Lysenkoism hasn’t fully disappeared. The rising phenomenon of ‘neo-Lysenkoism’ made headlines in late 2017, with proponents erroneously citing research on epigenetics to make their case. Neo-Lysenkoism has maintained the ideological nature of its predecessor, holding Lysenko up as a patriot deeply influenced by Soviet political ideologies and more questionably, Russian Orthodox Christianity. While the new eugenics movement has engaged with the failings of 20th-century eugenics, neo-Lysenokism has only doubled down on the legitimacy of 20th-century Lysenkoism, looking simply to defend its validity.
Vitamin C megadosing
So far, we’ve discussed flawed theories that have come to define the legacies of the individuals who promoted them. Now, let’s examine another such idea, but from a scientist who is otherwise regarded quite favorably.
Linus Pauling is an utterly towering figure in science: he received the 1954 Nobel Prize in Chemistry for his pioneering work on chemical bonds and was a serious contender in the race to uncover the structure of DNA. Pauling was also awarded the 1962 Nobel Peace Prize for his nuclear disarmament activism, making him one of only five two-time laureates. Later in life, however, Pauling advocated ‘orthomolecular medicine’, a form of alternative medicine focused on nutritional supplementation. Most famously, he championed the practice of vitamin C megadosing, ingesting vast quantities5 of the compound with the belief that it could mitigate or treat illnesses ranging from the common cold to schizophrenia and even cancer.
While vitamin pharmacology might have appeared to be within Pauling’s wheelhouse as a prolific chemist, his lack of skill as a clinical researcher actually led to a number of poorly-designed studies with misleading results. Pauling’s theories have never been accepted within mainstream medicine: they were subject to harsh criticism in their own time and are widely considered to be pseudoscience today. But like Lysenkoism, orthomolecular medicine has persisted into the 21st century, with particular attention given to its alleged antitumor potential.
I can think of a multitude of reasons for this phenomenon, including Pauling’s reputation as a legendary chemist and the enduring lack of pain-free cancer treatments. But my pick for the single biggest reason is the attractively simple picture of human health that megadosing paints. Just like the eugenicists, Pauling and other vitamin C acolytes fell victim to the tendency to molecularize and drastically simplify science.
CRISPR-Cas9 RNA targeting
One biological innovation much more likely to yield cancer treatments than orthomolecular medicine is the CRISPR-Cas9 system - a bacterial immune system that has been engineered into one of today’s most recognizable biotechnologies. The system is comprised of a protein called Cas9 that cuts DNA, and an RNA molecule called a ‘guide’ that directs the protein to cut at a specific DNA sequence, allowing for specific editing of genes in living cells. In late 2023, a mere decade after the system was first engineered to target DNA in a programmable manner, the first CRISPR-based gene therapy was approved by the US Food and Drug Adiministration to treat sickle cell anemia.
There was a time, however, when the fundamental biology of CRISPR-Cas9 wasn’t well understood: scientists were unsure how the system from bacteria from infection, meaning that there was no way to know that the system could be engineered. In fact, it was originally theorized that the system worked by cutting RNA rather than DNA6; the true mechanism was first described by researchers Luciano Marraffini and Erik Sontheimer in a 2008 paper. The crucial insight that CRISPR-Cas9 worked through DNA cleavage meant that it was possible to edit the genetic code itself, enabling the genome editing explosion of the last decade.
In recent years though, researchers have indeed discovered RNA-targeting Cas proteins - these editors fall into the Cas12 and Cas13 families, but in a sense, the original hypothesis did end up coming true. These proteins have been engineered for a variety of purposes, including multi-disease rapid diagnostic tests. While the original Cas9 system was the basis of the sickle cell treatment, much of the continued promise of CRISPR and other RNA-guided systems comes from the sheer number of applications enabled by their biochemical diversity. Even with the advent of the first CRISPR cures, expanding the ‘genome editing toolbox’ remains one of the field’s preeminent goals.
The organic Earth
The theories we’ve discussed today have come from a diverse set of subfields - from genetics to biological chemistry - but their relationship to the broader field of biology has generally been clear. Let’s discuss one final theory that attempted to harmonize biology with a more disparate field: geology.
The 18th-century natural philosopher James Hutton is often considered the founder of modern geology; he was the first to theorize that the Earth’s geological features were shaped by the gradual action of constant processes, rather than short-lived ‘catastrophes’. Hutton’s theory would come to be known as uniformitarianism and led him to realize that projecting natural forces backward in time could reveal truths about the Earth’s past. Not all of Hutton’s early geology was quite so prescient however: he also held that the Earth was a single “superorganism”, accordingly claiming that it should be studied physiologically.
Hutton’s theory, shaped by his deist beliefs, proposed that God engineered the Earth with the ability to perpetually sustain human life. Hutton envisioned a geological 'reproductive system' that allowed the Earth to renew itself continuously, an elegant design for a deity wishing to ensure humanity's survival without further divine intervention.For Hutton, the idea of an organic Earth was continuous with the rest of his geological theories, and he invoked it when predicting specific geological phenomena.
The theory helped Hutton predict the existence of two geological phenomena, granite veins in strata and angular unconformities, cementing it within the geological canon for decades to come. The philosopher of science Thomas Rossetter noted the irony of these predictions, writing that “constituents of Hutton's theory that would not be considered even approximately true today played various roles in generating them.” Hutton’s theory remained largely plausible until the early 20th century, when it was supplanted by the contracting Earth theory; this doctrine has in turn been pushed out by modern understandings of plate tectonics.
Though Hutton’s organic Earth theory has become largely obsolete, it has influenced new notions of symbiosis between living organisms and the environment. Most notable among these is the Gaia hypothesis, which holds that this symbiosis preserves the conditions necessary for life on Earth. Chemist James Lovelock and evolutionary biologist Lynn Margulis, the theory’s creators, have garnered both awards and criticism for their work: Lovelock won the Geological Society of London’s Wollaston Medal in 2006 but others have raised a number of scientific and philosophical objections to the hypothesis. Ultimately though, large-scale scientific syntheses such as Hutton’s organic Earth theory must incorporate knowledge from a vast number of disciplines; the very thing that underlies their conceptual novelty makes them difficult to defend.
I should acknowledge that I first encountered the genetic framing of the Oresteia while reading Siddhartha Mukherjee’s excellent book The Gene: An Intimate History. I’m always curious to see how scientific evidence is mobilized in non-scientific contexts (here, the ‘theater’ of the courtroom) and the influence of bad science on the trial of Orestes became the catalyst for this post accordingly.
I write “almost” here because children always inherit mitochondrial DNA from their parents. Also, there are some edge cases in which children inherit different numbers of chromosomes inherited from each parent, leading to disorders such as down syndrome and Klinefelter syndrome.
Lysenko typically referred to his doctrine as ‘Michurinism’, for the ‘father of Soviet biology’ Ivan Michurin. Throughout this section, I use ‘Lysenkoism’ for simplicity.
In his book How to Live Longer and Feel Better, Pauling recommended taking 6-18 grams of vitamin C daily. The recommended daily allowance is generally under 100 milligrams, with the upper limit being 2 grams.
Marraffini and Sontheimer allude to this in the introduction of their paper, but this is stated a lot more clearly in Walter Isaacson’s excellent account of the CRISPR story The Code Breaker: “Luciano Marraffini and his advisor Erik Sontheimer of Northwestern University in Chicago showed that the target of the CRISPR system was DNA. In other words, CRISPR did not work through RNA interference, which had been the general consensus when Banfield first approached Doudna. Instead, the CRISPR system targeted the DNA of the invading virus” (99).