Epigenetics are genetic traits which may or may not develop.
This includes forms of intelligence and skill whose expression depends at least partly on outside factors like education, upbringing, family background, cultural values and lifestyle.
How much of a difference do epigenetics make in intelligence versus hereditary, fixed DNA, and what triggers epigenomes?
Here’s what science tells us about how environmental factors affect gene expression relating to intelligence.
The young brain
Younger brains are more prone to change and develop in dynamic ways.
This can be seen, for example, in the much greater capacity of the younger individual to learn and retain new languages.
As the infant becomes a child, preteen, teen and young adult, the brain and neurology is still changing in numerous ways, particularly with regard to epigenetic expression.
The epigenome is the result of chemical changes to DNA that determines what part of them is more likely to be expressed or not.
It is a potential trait that emerges from DNA in some cases but not in others.
The epigenome may be developed or inhibited by outer physical factors or outer social and psychological factors.
As the Center for the Developing Child at Harvard University explains:
“The epigenome can be affected by positive experiences, such as supportive relationships and opportunities for learning, or negative influences such as environmental toxins or stressful life circumstances.”
As Harvard notes, “health, skills and resilience” are built up most neurologically and psychologically at a young age, and outer factors make a large difference.
If environmental factors hold that back, such as abuse, neglect, violence or lack of opportunity, difficult and long-lasting epigenetic changes may take place in the personality and cognizance of the young individual.
If, by contrast, positive environmental factors like a rich learning environment, support and enthusiastic opportunities are offered, this can trigger epigenetic traits of greater resilience, intelligence and cognizant ability in the young mind.
But how big of a difference do they make versus what you’re born with and how can we measure it?
Deeper than genes
There is a certain amount of intelligence that is inherited, particularly in terms of verbal, mathematical and spatial or visual intelligence.
The range of heritability for IQ (intelligence quotient) ranges from 57% to 80% according to which study you look at and the specific intellectual assessment or focus of the study.
The scientific consensus that has emerged over the past century is that you do inherit measurably more of your IQ than the intelligence you develop or lose due to outer reasons and environmental factors.
In other words, your inherited genes have a stronger impact on your intelligence than the impact of outer factors and influences on your genes that trigger the epigenome.
This does not mean that epigenetics are negligible or unimportant, however, which leads to continuing research into exactly how big of a difference outer factors make in increasing or decreasing somebody’s intelligence.
Indeed, researchers still debate just how much epigenetics may trigger a rise or fall in intelligence in various areas.
As Harvard notes:
“During development, the DNA that makes up our genes accumulates chemical marks that determine how much or little of the genes is expressed.
“This collection of chemical marks is known as the “epigenome.”
“The different experiences children have rearrange those chemical marks.”
Influential and reputed studies have traced the lives and IQs of identical twins with the same DNA and found they exhibited quite different personalities, aptitudes and intelligences based on their varied environments and the epigenetics that had been triggered by this.
The best way to judge the impact of epigenetics on intelligence is to take a look at a few examples of how they function.
Examples of epigenetic events
One of the most crucial examples of epigenetic expression is in
As Siobhán Dunphy explains in the European Scientist:
“Changes in DNA sequences can take millions of years to appear, whereas epigenetic changes happen much faster and can occur within one generation.”
Research from the Department of Psychiatry and Psychotherapy of Charité Universitätsmedizin Berlin found that the rise of average rates of scores on various tests shows a generally rising intelligence.
This type of change expresses a move from a century before that appears to be epigenetic and possibly related to improving living conditions, nutrition, education systems and literacy.
“The considerable increase in test results for average intelligence within one generation in the second half of the last century cannot be explained by genetics alone, which is where epigenetics comes in.”
The full impact and process of epigenetics is still being studied and analyzed.
What is known is that various genes express themselves and manifest under certain conditions.
Intelligence has been found to be directly affected by:
- Early upbringing
- Parental affection and support
- Strength of the community and familial network
- Level of trust and safety growing up
- Education and literacy received
- Nutrition, water, air quality and physical health
- Cultural influences, ideals and expectations
The influence of how we are raised and what surrounds us causes us to develop intelligence differently.
Essentially, the physical influences of our environment and the emotional and intellectual influences of our environment make us smarter or stupider than we otherwise might be.
This can go to a very literal level as well.
It’s not just about having good influences and high quality educational systems to bolster intelligence and trigger epigenetics.
A study from the National Institutes of Health (NIH) in the US found that children with more exposure to nature and “greenness” had higher IQ as a result of epigenetic triggering.
“We were specifically interested in the question of whether DNA methylation mediates the effects of exposure to greenness on children’s IQ…
“We found that the methylation levels … at age 2 were significantly associated with greenness exposure during early childhood.”
In other words, being more around nature and green trees and grass literally makes the methylation process in your DNA trigger an epigenome that makes you smarter.
The NIH researchers used the Wechsler Intelligence Scales to measure and compare the intelligence of kids in relation to exposure to greenness and any apparent effect that had on triggering the methylation process related to an increased IQ.
Zeroing in on epigenetics
It’s clear that epigenetics are real and wide-reaching in the effect on intelligence.
Many outside factors make us more or less intelligent, and it can be hard to list them all or measure them all.
But what’s certain is that intelligence is not only affected by outside factors, but also our cognitive and even decision-making capability is shaped by our environment in significant ways.
Looking back at the Universitätsmedizin research we can see several other interesting findings.
The researchers found very breakthrough results in their study of 1,500 teens in terms of just how big of a difference epigenetics can make in intelligence.
What they found was that the part of our brain that looks forward to a reward or generates enthusiasm or doubt in choices we are making becomes semi-permanently altered by the experiences we have.
They discovered that long-term epigenetic effects and even the way our brain perceives and processes the world is extremely affected by our environment, including the release of dopamine in our corpus striatum.
This part of the brain is very focused on making choices and becoming happy or excited in expectation of a reward.
“The researchers found a strong relationship between the epigenetic modifications of one particular gene and general IQ, suggesting our experiences not only affect the wiring of our brain, but the very way our genes function at a basic level.”
More wide-scale research certainly needs to be done with large and diverse control groups to find more specifics about exactly how much of a difference epigenetics can make in intelligence.
What’s clear is that epigenetics matter greatly and science is still on the cusp of discovering exactly how much they may alter or change the fixed DNA we are born with.