Many of you have probably heard of the old debate around how human behavior moves through generations concisely described as nature versus nurture. Or rather, is a human’s behavior primarily determined through their inheritance of genetic material (nature) or through the environment in which they develop (nurture)?
Largely, the answer has been determined to be both. And neither. That is, both play an important role and there are lots of factors that determine how big a role either of them plays at any given time in any given human for any given behavior.
And that whole area of study is called epigenetics.
The word epigenetic means “above the genome” and in this field, very simplistically, researchers look at how genetic material can be turned on or off (i.e., expressed or not) by our environments.
I’m just going to be transparent here and state a fact about which you probably already have a sneaking suspicion, but I still feel it necessary to disclose: I am no expert in epigenetics. In fact, I don’t consider myself an expert in any field of scientific study. I simply have a bit of experience reading and interpreting scientific studies and well, I confess to being a connoisseur of books that fall into what you might call the “self-help” genre.
Now, before you go conjuring images of crystals and chanting (of which there is certainly that), the truth is that with advances in neuroscience, many in the self-help genre are backed by legit scientific credentials and, some really fascinating research. One such study, from the field of epigenetics, that I have seen referred to I don’t know how many times, is the rat-licking study.
I know - super cringe-worthy - but please, stick with me.
First, I’ll just start by calling the licking behavior “grooming” and get that out of the way.
Then we can say, that researchers observed that grooming behavior by rat mothers towards their pups varied, with some providing more grooming and some providing less. The highly groomed pups went on to be high-groomers themselves and, as you might expect, the less groomed became low-groomers.
Score one for nurture.
However, when researchers measured hormone production as a marker for biology, they also saw a difference. The highly-groomed produced lower levels of stress hormones, while the low-groomed produced greater levels of these hormones suggesting that they had decreased capacity to manage stress; a decreased capacity that followed them throughout adulthood and was passed on to their pups.
Nature has tied it 1-1.
The really mind-blowing part though, was that when researchers put pups born to low-grooming mothers with surrogate high-grooming mothers, things changed. Not only did they become high-groomers themselves and pass this behavior along to their offspring, they also exhibited a decrease in hormone production, which they, again, passed along to their pups.
This means that there’s an environmental component and a genetic component, but that neither is fixed, not even the biology. Both can be altered and this alteration can be sustained in later generations.
Said another way, low-groomed pups inherited the biologic machinery that led to worse stress management, but it was turned off when they found themselves in a more nurturing environment. AND that machinery was passed on in the off position.
And while I’ve grossly over-simplified this really important research, I’ve done so because there are some incredibly noteworthy takeaways from even a basic discussion of its findings.
One is that the effects of trauma can be passed down through generations in our very DNA.
You might read that again and then pause. Really let it sink in.
Because we now also have evidence that the effects of trauma have far-reaching impacts on not just our mental health, but on our physical health as well, most notably, through production of stress hormones, which can lead to chronic inflammation and have long-term effects on our immune systems, for instance.
So trauma and stress can make us sicker and make our children sicker, our grandchildren sicker, and so on.
Think about this in terms of one group being chronically oppressed by another, which it might be redundant to point out but I will anyway, is traumatic and stressful.
A second takeaway is that it doesn’t have to be this way.
Once again, let’s pause.
If families and their subsequent generations were less traumatized and stressed then they could be healthier - or at least at less risk of being unhealthy - at a genetic level. And even a cursory knowledge of healthcare statistics in our country, that is who’s less healthy than whom should lead to an understanding of just how meaningful this could be.
For a great discussion of this in action, check out Nadine Burke Harris’ The Deepest Well: Healing the Long-Term Effects of Childhood Adversity.
Or if you want to go further into the research, read the review "Epigenetic Mechanisms and the Transgenerational Effects of Maternal Care” by Frances A. Champagne.