May 17, 2019, by Brigitte Nerlich

Witness marks: On the trail of an epigenetic metaphor

This is a guest post by Aleksandra Stelmach, University of Nottingham, Institute for Science and Society

In a previous post Brigitte Nerlich and I briefly discussed the emergence of a seemingly new metaphor used in popular discussion about epigenetic effects of nutrition on offspring and, potentially, future generations. In this post I try to track down the origins of the metaphor ‘witness marks’ which Charlotte Church used for ‘epigenetic marks’ in her article on epigenetics and junk food.

I found two potential sources for this metaphor. One source may be discourses in forensic epigenetic. Another source may be discourses around the contested topic of transgenerational epigenetic inheritance.

Forensic epigenetics

My first guess is that the phrase ‘witness marks’ is somehow related to the field of forensic epigenetics (and also genetics). A witness or an eye-witness is a legal concept, and it denotes a person giving evidence. In forensic epigenetics samples gathered at the crime scene are believed to provide vital information that can be used in court. Such information is revealed through the analysis of the epigenetic marks, especially of the DNA methylation that Charlotte Church also mentioned in her piece.

An article published in Forensic Magazine explains forensic epigenetics in the following way: ‘We all put wear and tear on our DNA. Although we are born with a certain highly unique genetic code, the things we do—from diet to exercise, alcohol to smoking—cause methylation changes at our very fundamental biological core. Such DNA methylation has been the focus of countless health-focused scientific investigations’.

Phenotyping and fingerprinting

The author of the article explains that the methylation changes are correlated with a range of factors, from the age of the person, some type of cancers, post-traumatic stress disorder and even socio-economic status – the traits that could help profile the potential suspect. The author suggests that an analysis of epigenetic marks, though useful, could be imperfect. There is an ethical concern that ‘innocent bystanders in addition to potential perpetrators could lose privacy protections. Phenotyping could mislead police investigations—like if the genetic changes showed a smoker, but the real criminal was not one, for instance.’

A similar imaginary of the potential of the analysis of epigenetic marks underpins an article published in Genome Biology and titled: ‘From forensic epigenetics to forensic epigenomics: broadening DNA investigative intelligence’.

In this article the authors outline the ways in which epigenetics and epigenomics can be used forensically, from determining the type of cells contained in the sample from the crime scene, to determining the age. They also hope that ‘Provided that scientific and technological progress in human epigenomics continues to advance rapidly, we envision the establishment of an “epigenomic fingerprint” from crime scene traces as a promising approach to address various forensically relevant questions that cannot be answered through genetics.’ In future, the analysis of the DNA methylation might also tell us if the person whose biological material is tested is a smoker, a drinker, a drug user, if they are physically active, whether they follow a particular diet, what their body size is and so on.

A popular article summarising this research claimed that ‘DNA evidence could soon tell cops your age, whether you smoke, and what you ate for breakfast. Epigenetic markers on DNA can reveal far more intricate details about someone than current techniques’. Such analysis of epigenetic marks is also called ‘phenotyping’. ‘The computer-generated picture comes from a new forensic technique called DNA phenotyping, which provides clues about the physical appearance of a criminal in the absence of a suspect or clear description form witnesses’.

DNA witnesses

In the scientific and popular texts on forensic epigenetics we have not found the metaphor of epigenetic ‘witness marks’. However, the idea that DNA can provide vital information about the perpetrator of a crime has been used in the context of forensic genetics. In the USA there is even a forensic testing technology called ‘DNA Witness’.

According to anthropologist Duana Fullwiley ‘”The name is not accidental. Its inventors at DNA Print Genomics Inc. want to convey the idea that this technology itself embodies the power of the ‘expert witness’ through literal genotypes, or “base-calls,” of the perpetrator’s specific DNA nucleotide pairs’. A popular article on the use of the DNA Witness’ technology for racial profiling by police can be found here.

I also found a website of a company offering services of DNA expert witnesses. It says that ‘DNA expert witnesses are often skilled with laboratory testing in relation to blood, hair, serology, toxicology, fingerprint examination, polymerase chain reaction (P.C.R.), and other issues possibly involved with criminology and evidence analysis.’

In sum, we have found the metaphor of ‘the DNA witness’, which denotes a testing technology that can be used to determine a genotype and to identify a suspect of a crime. The field of forensic epigenetics draws on similar assumptions and frames epigenetic marks as the source of evidence, indeed as ‘epigenomic fingerprints’. Here the DNA methylation may (now or in the future) help reveal various traits of the perpetrator (including their type of diet!) and help determine their identity.

If this guess is correct, then the use of forensic imaginary in the context of mother-blame shouldn’t come as a surprise. In public discourses mothers are often portrayed as responsible for various health problems of their children. They are even framed as ‘smoking guns’ as anthropologist Meghan Warin and colleagues argued in an article on the intergenerational transmission of obesity.

Markers of intergenerational trauma

My second guess is that the ‘witness marks’ metaphor is somehow related to discourses on inter/transgenerational transmission of trauma. Although here this is perhaps a bit more difficult to pinpoint. The general idea underpinning this type of discourse is that people can experience trauma without having lived through it themselves, i.e. without actually witnessing war, natural disaster, violence, etc.

This is illustrated by a popular article reporting on research on intergenerational trauma and epigenetics conducted by Rachel Yehuda. ‘Yehuda and her team examined 32 Holocaust survivors. These were Jewish men and women who had either experienced or witnessed torture, had been in hiding, or had been imprisoned in a Nazi concentration camp. By analyzing the genes of their children and comparing the results to those of Jewish families who were not living in Europe at the time of WWII, they were able to identify genetic changes could only be attributed to their parents’ experiences in the Holocaust’.

Similar configurations can be found here: ‘Dr. Yehuda’s initial studies confirmed that Holocaust survivors have altered levels of circulating cortisol compared with other Jewish adults of the same age. She then turned to look at the children of Holocaust survivors, investigating the prevalence of stress and exposure to trauma, along with current and lifetime PTSD and other psychiatric diagnoses between them and a control group of comparable demographics. The results showed that although both groups experienced a similar number of traumatic events, the children of Holocaust survivors had an increased vulnerability to PTSD and other psychiatric disorders compared to the control group. More specifically, maternal PTSD resulted in lower cortisol production in adult offspring of Holocaust survivors. The children in Dr. Yehuda’s studies were conceived after parents had directly witnessed the Holocaust, highlighting the idea that trauma-related changes to parental biology can result in accompanying changes to offspring biology, making the Holocaust survivor children vulnerable to these same conditions.’ (It should be said that Yehuda has now issued statements toning down the significance of her findings and criticising the media)


Witnessing is also a specialist term in psychoanalysis and working with trauma (see here).

A whole article on intergenerational transmission of trauma (especially in the context of the Holocaust), on witnessing and remembering (but not on epigenetics) can be found here. It says (referring to the next generation of people experiencing trauma): ‘Postmemory describes the relationship that the generation after those who witnessed cultural or collective trauma bears to the experiences of those who came before, experiences that they “remember” only by means of the stories, images, and behaviors among which they grew up. But these experiences were transmitted to them so deeply and affectively as to seem to constitute memories in their own right. Postmemory’s connection to the past is thus not actually mediated by recall but by imaginative investment, projection, and creation.’

The idea of witnessing is thus woven into the discourses on intergenerational transmission of trauma, just as it is woven into forensic epigenetics.

Witness marks

We don’t know whether any of these sources were actually the sources for the phrase ‘witness marks’ as a metaphor for epigenetic marks used by Charlotte Church. However, epigenetic discourses around forensics and most importantly intergenerational epigenetic inheritance are ‘in the air’ and, contested by scientists or not, they infiltrate thinking about nature and nurture, genes and environment, body and society. Such discourses leave traces in popular culture and the metaphor of ‘witness marks’ is just one of them.


Here is a tweet from Charlotte Church: “Really interesting article. Thanks for furthering discussion. For the record (and as far as I’m aware) it was my husband who came up with the “witness marks” metaphor. He’s not a scientist but is a fan of S-Town. Hope this clears things up.” (And for those who don’t know S-town:

Image: Pixabay


Posted in epigeneticsMetaphorsScience Communication