You Are What Your Genes Experience
When asked to answer the question “Who Are You?” at the Next Big Question event in 2011, Clyde Hertzman’s argument was that "You Are What Your Genes Experience." Dr. Hertzman is an epidemiologist and Fellow in our Successful Societies program and our Experience-based Brain & Biological Development program.
When asked to answer the question “Who Are You?” at the Next Big Question event in 2011, Clyde Hertzman’s argument was that "You Are What Your Genes Experience."
Dr. Hertzman is an epidemiologist and Fellow in our Successful Societies program and our Experience-based Brain & Biological Development program.
The nature/nurture dilemma has long framed debates about the relative importance of genes and environment on human development. For Clyde Hertzman, who is a professor of population health at the University of British Columbia, the question is far more nuanced. Ongoing research illustrates how, rather than genes being responsible for one job and environmental factors for another, the real story centres around how nature and nurture interact with one another.
Events in the external world can leave biochemical fingerprints on a child’s DNA, changing the course of everything from brain complexity to motor skills – some of the fundamental characteristics of individual identity.
“We’re coming to understand now that early experience gets under the skin,” he says.
That thesis holds enormous implications for early childhood education, parenting techniques and health policy. The phenomenon also suggests that an individual’s genetic make-up is programmed to adapt during the formative early years to both positive and negative external stimuli.
The mechanics of this process involve subtle changes in brain chemistry. When very young children experience things – anything from the soothing sound of a parent’s voice or the screams emanating from a domestic assault – those occurrences are carried into the brain in the form of electrical signals. Stress-inducing experiences are associated with heightened cortisol levels, Hertzman says. These signals create a kind of biochemical “cascade” that can trigger structural and chemical changes to cytosine, one of the four building-block components of DNA. The cascade leaves behind distinctive patterns of a methyl compound, which in turn affects the way these genes will express themselves.
This is “the outside world and DNA talking to one another,” he says.
Animal and early human studies on blood and saliva cells suggest that methylation patterns differ noticeably with exposure to positive and negative stimuli.
“Right now, we’re at the statistical association point,” Hertzman says, noting that researchers thus far have had to infer methylation patterns in brain tissue.
How gene-environment interactions affect children’s development and help shape their identities may be “way upstream,” affecting not only the brain circuits that regulate stress hormones, but also the evolution of the organ systems that manufacture these hormones.
“Preliminary evidence suggests that the capacity of early experience to leave epigenetic marks is greater than with later experiences,” Hertzman says, (although the phenomenon has also been observed among people who have endured profoundly traumatic experiences later in life, including living through the Holocaust).
It may also be the case that these changes are intergenerational, explaining how the effects of trauma can indeed be passed from parent to child."