In Brief
- Genes are not a fixed program but a repertoire — an enormous library of survival strategies, of which only a fraction are ever activated in any individual lifetime.
- The primary determinants of which genes express are environmental signals and internal physiological states — not the sequence of the genome itself.
- Korean medicine arrived at a functionally equivalent conclusion centuries before epigenetics: the same constitutional pattern produces radically different outcomes depending on the patient’s lived environment and emotional state.
- Genetic determinism remains clinically dangerous not because it is entirely wrong, but because it produces therapeutic nihilism — the belief that nothing can be meaningfully changed.
I teach pathology at a Korean medicine university, which means I spend a significant part of my professional life at the intersection of molecular biology and traditional medical theory. From that position, the rise and now partial fall of genetic determinism has been one of the most instructive episodes in modern medicine — not for what it discovered, but for what it assumed.
The Selfish Gene and Its Clinical Consequences
Richard Dawkins’ 1976 formulation — that organisms are essentially vehicles for the replication of selfish genes — was philosophically provocative and scientifically partial. The partial truth it captured was real: natural selection does operate primarily at the level of the gene. But the clinical extrapolation that followed was neither warranted nor benign.
If genes are the primary causal factor in disease, then the logical clinical posture is to identify the relevant genes and either replace them, suppress them, or accept their consequences. This posture has driven enormous research investment, some of it productive. But it has also produced a generation of patients who believe, sometimes quite explicitly, that their health trajectory was fixed at conception.
This is the belief I encounter most consistently in clinical practice, and it is the belief I work hardest to correct.
What Epigenetics Actually Established
Epigenetics — the study of heritable changes in gene expression that do not involve changes to the DNA sequence — did not overturn genetics. It complicated it in ways that are clinically very important.
The genome, we now understand, is not a program that runs identically in every context. It is more accurately described as a repository of conditional instructions. Each gene contains regulatory regions — promoters, enhancers, silencers — that function as switches. Environmental signals, including nutrition, stress hormones, inflammatory cytokines, and even social experience, reach these switches through biochemical cascades and alter which genes are expressed and at what levels.
The practical consequence is significant: two individuals with identical genetic sequences can display substantially different disease susceptibilities depending on the epigenetic state of their cells. And critically, epigenetic states are modifiable. They respond to interventions.
This is not the popular version of epigenetics, which often overstates plasticity and implies that belief alone can reprogram disease. The truth is more constrained and more interesting: the environment — including the internal biochemical environment produced by psychological states — shapes gene expression within limits set by the genome.
Korean Medicine and Epigenetic Logic
Korean medicine developed its own framework for understanding why constitutional diagnosis produces such variable outcomes across individuals. The concept of jilbyeong — roughly, constitutional predisposition to disease — does not assert that a given constitution inevitably produces a given disease. It asserts that a given constitution creates a particular pattern of vulnerability that manifests or fails to manifest depending on environmental and behavioral factors.
This is functionally equivalent to what we now describe epigenetically: the genome creates a landscape of possibilities, and the environment selects among them.
What is striking is that classical Korean medical texts show particular attention to emotional and psychological states as drivers of constitutional change. The Sasang typology, for instance, correlates specific emotional tendencies with specific physiological patterns — and recommends emotional cultivation as a medical intervention. This implies, centuries before molecular biology, that internal states have physiological consequences that shape disease susceptibility.
We now have mechanistic explanations for how this works. Chronic psychological stress produces sustained elevation of cortisol and pro-inflammatory cytokines. These signals reach gene regulatory regions and alter expression patterns in ways that increase susceptibility to cardiovascular disease, metabolic syndrome, and immune dysfunction. The Korean physicians did not know the mechanism. They observed the pattern and formalized it.
The Problem with Genetic Fatalism in the Consulting Room
I want to be specific about the clinical harm produced by misapplied genetic determinism, because it is real and I see it regularly.
Patients who have been told they have a genetic predisposition to a particular disease — heart disease, diabetes, certain cancers — frequently interpret this information as a sentence rather than a warning. They stop modifying risk factors because they believe modification is futile. They disengage from preventive behaviors precisely when those behaviors are most important. Occasionally they develop a kind of pre-emptive grief that itself constitutes a psychological stressor with documented physiological effects.
This is not a misunderstanding produced by ignorance. It is produced by the language clinicians use when communicating genetic risk. “You have the gene for X” implies a deterministic relationship that does not exist for most complex diseases. “You have a genetic variant that increases your relative risk of X under certain environmental conditions” is accurate but rarely how the conversation goes.
The distinction matters enormously for patient behavior.
The Limits of the Opposite Error
I should also be clear about what epigenetics does not justify. The popular extrapolation — that our beliefs directly reprogram our DNA, that disease is primarily the product of negative thinking, that sufficient positivity can cure cancer — is not supported by the evidence and is clinically harmful in a different direction.
Patients who believe that illness is the consequence of insufficient positive thinking bear an additional burden of self-blame that interferes with appropriate medical care. The claim that Bruce Lipton’s “biology of belief” framework, in its popular form, gives patients full authorship over their genetic expression is a misrepresentation of what epigenetics shows.
What the evidence supports is more modest and more actionable: environmental and behavioral factors modify gene expression in ways that have meaningful effects on disease risk and progression. Diet, exercise, stress management, sleep, social connection — these are not alternatives to genetics. They are the variables through which the genome produces its actual expression in a given body over a given lifetime.
A Clinical Framework That Integrates Both
In practice, I encourage patients to hold two ideas simultaneously. First: your genome is real, and it creates genuine patterns of vulnerability and resilience that cannot be wished away. Second: the environment in which your genome operates is substantially within your influence, and that influence is not trivial.
Korean medicine, at its most sophisticated, has always operated from this dual premise. The constitutional diagnosis identifies the genome’s landscape. The clinical intervention addresses the environmental variables that determine where on that landscape the patient currently stands — and where they might move.
Genetic determinism abandoned this second dimension. Epigenetic research has restored it. The clinical task now is to communicate it in a way that produces appropriate action rather than either fatalism or magical thinking.
This article reflects the clinical observations and teaching practice of Professor Seungho Baek, Professor of Korean Medicine at Dongguk University College of Korean Medicine, specializing in Pathology and Oncology.
