How would your thinking about the world change if you discovered that what you – “experienced” in your lifetime – could actually change the genetic inheritance you pass on to your future child?
How would it impact your thinking if you knew that joining the military, fighting in a war and developing PTSD wouldn’t simply be a psychological and interpersonal challenge for you and your family upon your return? What if you knew in fact that your war experiences could/would be passed on to your unborn children impacting their own ability to cope with their life stressors. What if you also knew that without any “war experience” of their own directly impacting them, your children might in turn pass those same changes on to their as yet unborn children? How might our entire way of seeing our world transform if we could in fact simply and clearly grasp the awesome significance of this proposition?
Perhaps the most paradigm shattering research findings of the last 100 years may be in the relatively new field of epigenetics. This is an area of study that looks at among other things, how experiences in one generation may in some way(s) be passed on to subsequent generations through changes in how genes are expressed. This does not involve changes to our DNA , but instead involves a process referred to as “methalyation” which determines “how” and/or “if” certain genes are “expressed” or activated in ourselves and sometimes in our offspring. But first a look back.
Jean-Baptiste Lamarck, in the 18th century, postulated that giraffes eventually developed their long necks because over many generations they were always reaching for food high up in trees out of easy reach. His proposition that experiential events that occur in one generation could somehow physiologically transmit to a subsequent generation became seen by the majority of the scientific community as simply implausible. The prevailing wisdom of the new genetic sciences became that it is our “genes” which control not only our, but subsequently our offspring’s inheritance. Genetic science made allowances for the mutation of DNA in random fashion, impacting the process of natural selection and evolution. However, the idea that “how” I lived my life and “what” I experienced could in some fashion change the genetic inheritance of my offspring was seen as, well, “Lamarkian,” and therefore an example of a quite untenable heresy.
Over decades the idea developed that we would someday break our genetic code, and discover “which gene” controlled whether one developed diabetes, heart disease, colon cancer, schizophrenia and other diseases showing evidence of links to our inheritance. Sure we acknowledged that our “lifestyle” habits, i.e. smoking, drinking, diet, exercise, or lack there of, could play a certain limited role in whether we did in fact develop a disease, but “genetic predisposition,” became a favored perspective to explain why say, diabetes and heart disease run in my family inter-generationally, but not in yours.
One can think of this as essentially another version of the “nature versus nurture” debate that resonated through not only biology but psychology as well. During my undergraduate study in psychology in the early 1970’s the debate raged as to whether schizophrenia was the result of family communication patterns and perhaps other socio-economic factors (nurture), or from strictly genetic factors (nature).
Twin studies were presented as evidence of “genetic predisposition.” When twins separated at birth and raised in different environments both developed schizophenia, this was viewed as strong evidence of the “genetic” factor in inheriting the disease. For many these quantitative – (“hard science”) findings trumped the qualitative (“observations”) of the social scienses. The observation and qualitative recording of the disturbed dynamics in some families with a schizophrenic member, were seen as somehow less “objective” and therefore less trustworthy by those swayed by the “genetic” evidence. Early in my studies one of my psychology professors stated that perhaps someday we’ll discover it is “both nature and nurture.” Given our new findings in the emerging field of epigenetics, it would appear his prediction has proven quite accurate.
This post will not attempt in any way to do justice to the complexity and constantly unfolding research in this newly emerging field of study. However, I will share some of the research findings, and links to further reading. Epigenetic research sheds invaluable new light on our recently discovered, though long overdue, “new understanding,” that nature and nurture are engaged hand in hand in the human historical drama of our individual and collective intergenerational inheritance.
Scientific research in the late 1990’s showed that how much or how little a mother mouse licks her newborn offspring creates lasting impacts upon the infant mouse’s nervous system by virtue of how stress hormones are later expressed in adulthood. Essentially, the more maternal licking behavior, the lower the amount of stress hormones when the baby mouse is grown, and the calmer the mouse is when faced with stressful situations.
Subsequent research examining the brains of the now grownup baby mice found that differences existed between the brains of those with attentive mothers versus those with inattentive mothers. Those with inattentive mothers had highly “methylated” genes that help regulate the body and brain’s sensitivity to stress hormones. Those with attentive mother’s did not show this feature.
The simplest way to consider this finding (though it is admittedly an oversimplification) is that the behavior of the respective mouse mothers either “turned on” or “turned off” genes in their babies, whose function was to regulate sensitivity to stress hormones when those babies reached adulthood.
Later research found that another physiological impact of inattentive mothering was the methylation of genes for estrogen receptors in the brain of the baby mice. When these mice became adult mothers the methylation of thosed genes, that took place when they were babies, physiologically caused them to show less attentive mothering to their offspring. Amazing!
Other research has examined the impact upon mouse offspring if mother is removed for even short periods during infancy, versus normal upbringing with mother always present. The results showed significant changes in the ability of those mice with interrupted maternal care to later in life manage stressful situations compared with those with no maternal interruption. Of perhaps even greater note, was that this impairment in stress response was seen in the subsequent generation with no further experimental intervention or manipulation. In other words, the impairment in the stress response physiology of the next generation had been impacted “epigenetically,” through the methylation of genes that actually passed from one generation to the next.
Research has been done comparing post-mortem examination of the brains of humans who have experienced child abuse, versus those without abuse. Those with abuse histories show a different epigenetic profile from those without abuse. Childhood exposure to witnessing domestic violence, exposure to toxins in diet or environment, poor nutrition and/or maternal stress ALL have been shown to alter the epigenetic expression of genes in offspring. Alterations which themselves may then be passed on to another subsequent generation.
Research into the impacts on the physiology of the offspring of Holocaust survivors has shown they experienced epigenetic changes which resulted in increased levels of depression and anxiety. This is true, though they never experienced the Holocaust themselves, but only through the epigenetic alteration of their genes.
Parallel findings are being documented when researchers examine First Nations people in Canada whose parents, grandparents, and even great-grandparents survived the often intense trauma of attending the Native boarding schools. These schools not only subjected Native children to what is today considered literally “cultural genocide,” but were places where children also suffered routine sexual, emotional and physical abuse, and neglect, while miles away from any family support or contact.
Returning to research into epigenetic changes created in laboratory mice: ((”The idea that traumatic stress responses may alter the regulation of genes in the germline cells in males means that these stress effects may be passed across generations. It is distressing to think that the negative consequences of exposure to horrible life events could cross generations,” commented Dr. John Krystal, Editor of Biological Psychiatry.”))
More recent research was conducted in which adult mice were exposed to mild electric shock at the same time they were exposed to the odor of acetophenone, which has a scent similar to cherries. Not surprising is that these same mice would respond with shuddering and other stress responses when later exposed to this “cherry” scent without any electric shock. What is truly amazing as an epigenetic finding is that not only did the next generation show this same “shuddering” response when exposed to the scent of acetophenone, but the “grandchildren” did also! In vitro fertilization using sperm from mice exposed to acetophenone and electric shock ALSO produced offspring exhibiting this shuddering response. Other research has shown the response can be transmitted through the mother also. By way of explanation researchers found that brain structures in the mice that processed odors had been epigenetically altered, creating an effect that could be passed down through generations.
Epigenetic research is challenging Western science and philosophy at foundational levels regarding our concepts of just what might be our – “human nature.” However, many Native Americans and Alaskan Natives do not find the new research quite so revolutionary:
((“Folks in Indian country wonder what took science so long to catch up with traditional Native knowledge. ‘Native healers, medicine people and elders have always known this and it is common knowledge in Native oral traditions,’ according to LeManuel ‘Lee’ Bitsoi, Navajo, PhD Research Associate in Genetics at Harvard University during his presentation at the Gateway to Discovery conference in 2013.”))
The epidemic levels of suicide, depression, addiction and type II diabetes in “Indian Country” deserve reconceptualization through the lens of recent epigenetic findings.((“Another researcher Bonnie Duran, an associate professor at the University of Washington, calls this a “colonial health deficit.” Not only does this new study illuminate the long-term effects of the suffering of Holocaust survivors and Native Americans, but it also suggests an intriguing avenue for future research: whether victims of other historic or ongoing genocides, such as America’s black and brown population or the millions of those killed in U.S. wars in the Middle East, also suffer from a colonial health deficit.”))
My own intellectual journey began as a white, male therapist whose grandparents all immigrated from Poland just prior to WWI. In working with trauma and addiction services as a therapist working in Native Alaskan mental health services, I first encountered the impact of intergenerational epigenetic trauma on Native peoples.
The emerging knowledge from the Adverse Childhood Experiences Study, the newest neurobiological research into how trauma impacts the brain, and finally the epigenetic research into trans-generational transmission of trauma impacts have left me questioning everything I have been taught about emotional and physical health and illness.
This research has totally transformed my understanding regarding what it is to be human, and to consider with great seriousness how my own inter-generational trauma history as a white male of European origins impacts not only me, but the entire Western paradigm that has shaped psychology, sociology, history, philosophy, biology and other sciences.
We are ALL CHILDREN OF TRAUMA. This is quite clear by even the most cursory examination of the Western historical record and the 500 plus years of ongoing colonial warfare we in the West have been engaged in. How has and how does this ongoing history of war, slavery, genocide, mass starvation, and collective trauma impact us today? How does it shape the lenses through which we view ourselves, each other and the world? How does it limit our ability to even imagine alternative paradigm, a world perhaps in which violence and mass trauma was not viewed as “natural” and “inevitable?”
Links to epigenetic research and analysis: