Imagine an 1864 Confederate POW camp. Because of the extreme overcrowding, each prisoner took up about the same amount of space as a grave, according to historians. Union soldiers subsisted on meager corn rations, and many of them perished from scurvy and dysentery as their bodies deteriorated in environments that were, by definition, meant to break people.
The men who survived had obvious consequences, including reduced prospects, shortened life expectancies, and poor health. That is not shocking. Surprisingly, the damage didn’t end with the survivors, as researchers piecing together historical mortality records eventually found. Compared to the general population, their sons’ mortality rates were higher. Their grandsons did the same. Men who had grown up well-fed and well-cared for, who had never been in a Civil War prison camp, were carrying something from a grandfather’s suffering that neither they nor anyone else could see.
| Field | Details |
|---|---|
| Field of Study | Epigenetics — the science of heritable gene expression changes without DNA sequence alteration |
| Key Mechanism | DNA methylation, histone modification, noncoding RNA regulation |
| First Major Human Studies | Dutch Hunger Winter (WWII), Holocaust survivor offspring research |
| Historical Case Study | U.S. Civil War Confederate POW camp survivors — effects observed in sons and grandsons |
| Estimated Global PTSD Prevalence | ~5.6% of trauma-exposed individuals (approx. 70% of global population experiences trauma) |
| Key Concept | Transgenerational epigenetic inheritance — epigenetic marks passed beyond direct offspring |
| Notable Publication | OxJournal — Epigenetic Inheritance of Trauma Across Generations (Sept. 2025) |
| Therapeutic Implication | Environmental enrichment therapy shows potential to reverse some epigenetic trauma markers |
| Key Distinction | Epigenetics changes gene expression — it does NOT alter the underlying DNA sequence |
| Reference Website | National Institutes of Health – PMC Epigenetics Research |
This is the point at which epigenetics enters the narrative, and its implications are still being worked out. The study of how gene expression varies without changing the underlying DNA sequence—that is, how an individual’s experiences can affect how their genetic code is interpreted—is known as epigenetics. Small chemical changes, mostly caused by DNA methylation, function similarly to annotations in a book’s margins.
The text remains unchanged. However, the notes dictate which passages are read, which are skipped, and which are read so forcefully that the body begins to arrange itself around them. A person’s body responds to severe trauma by changing the genes that are active, essentially attempting to prepare the organism for a dangerous environment. Some of those annotations seem to be passed along, which is concerning. To kids. To grandchildren at times.
Drawing from some of the most well-documented disasters of the 20th century, the research proving this has been developing for decades. When compared to siblings born before or after the famine, studies of children born to Dutch women who were pregnant during the 1944–45 famine—during which the Nazi occupation reduced civilian food supplies to almost starvation levels—found discernible differences in gene methylation patterns.
Researchers have found that individuals who inherited their parents’ biological reactions to events they did not personally witness had altered stress hormone profiles and increased susceptibility to PTSD, making Holocaust survivor offspring one of the most studied groups in this field. At first, there was a great deal of skepticism regarding the possibility that suffering could be biologically passed from parent to child—not through learned behavior or storytelling, but rather through the actual molecular machinery of heredity.
It was at odds with the prevailing theory of genetics, which maintained that an individual’s life experiences remain within their lifetime and do not alter their genetic makeup. The field continues to be fascinated by the revisions being made to that model.
When you sit with this research long enough, it’s difficult to avoid feeling its weight. Approximately 5.6% of people worldwide will develop post-traumatic stress disorder (PTSD), which is characterized by intrusive memories, emotional dysregulation, hypervigilance, and a nervous system that essentially never fully stops being alert. It is estimated that 70% of people will encounter a potentially traumatic event at some point in their lives.
Public health systems have hardly started to account for the extent of inherited suffering that is subtly ingrained in the world’s population if even a fraction of that biological patterning is passed on to progeny. Healthcare that is trauma-informed typically concentrates on the person who was affected by the incident. According to this research, the circle of concern might need to be significantly expanded.
DNA methylation, histone modification, and noncoding RNA action are the three main mechanisms that scientists are monitoring; each of these mechanisms represents a distinct way that the environment can influence gene behavior. The most researched is DNA methylation, which affects which genes are expressed and to what degree by attaching methyl groups to particular locations in the DNA. DNA accessibility is regulated by histone modification; tightly wound genes are more difficult for the cell’s machinery to access and read.
As regulatory signals, noncoding RNAs adjust expression in ways that scientists are still figuring out. These mechanisms are similar in that they are sensitive to experience and, crucially, have the capacity to endure reproduction and manifest in the cells of the subsequent generation. Although the precise frequency and circumstances of this transmission in humans are still unknown, evidence from both animal models and human population studies is steadily mounting.
This research has a cautiously optimistic undertone. Unlike genetic mutations, epigenetic marks are not permanent. They are able to move. In animal studies, environmental enrichment therapy—interventions that introduce positive, stabilizing experiences like safe relationships, less stress exposure, and therapeutic support—has shown promise in reversing some trauma-related epigenetic changes. According to one researcher, even if the alphabet cannot be altered, the story can.
This framing is helpful because it shifts the question from “are we permanently damaged by what our ancestors endured?” to “what conditions allow the damage to ease?” Therapeutic strategies that take this biological layer into consideration may eventually function differently and more successfully than those that only address trauma as a psychological issue.
As this field advances, it seems as though science is gradually catching up to what many communities—such as the descendants of enslaved people, refugees, war survivors, and populations affected by famine—have long understood intuitively. Between generations, the burden of collective suffering does not go away. Sometimes it manifests itself clearly in behavior and memory, and other times it manifests itself subtly in biology.
Since the mechanisms are still being mapped and the human evidence is still catching up to the animal studies, researchers are cautious to point out that epigenetics is not yet a precise science. However, the research’s direction is fairly obvious. People’s experiences, even the most severe and violent ones, leave a biological imprint. It turns out that there are places for that trace to go.
