Why Are We All Different?

Tom Boyce is a Professor at UCSF School of Medicine and Marla Sokolowski is a University Professor at the Department of Ecology & Evolutionary Biology, University of Toronto. The Interview was conducted prior to this year’s Jacobs Foundation Conference at Marbach Castle on Lake Constance, Germany. The conference brought together leading scientists from a variety of disciplines to discuss current and future research on Reconciling Genes and Contexts.

Recent scientific research has confirmed that the interplay of genetic variation and the social environment guides brain development like in both fetal and early postnatal life. What can expectant parents do to positively influence the brain development of their child?
Tom Boyce: In paediatrics we like to say that all parents think that the environmental totally determines the behaviour and health of their child until they have their child and then they think that the child’s characteristics are genetically determined. However, thinking that everything about a child is from the genes or alternatively from the environment is not correct. It is a combination of both genes and environment. The interaction between parent and child is really crucial especially in the early years.

Marla Sokolowski: During this time, a child’s brain is like a sponge. Your child has many billions of neurons and they get sculpted by the experience that they have. Sound and sight, touch and comfort, language through songs and stories, all of the things that we do with a very young infant helps that child’s brain develop. As the child gets older the language continues to develop as does the child’s social emotional development. The experience that the child receives prenatally and in early life is absolutely critical for a child to develop well and reach its potential.

Is there anything parents should avoid?
Marla Sokolowski: Parents should not neglect their children. People think that being abusive physically or sexually or mentally abusive is terrible which of course it is but what our colleague used to call, “The slow drip of neglect,” can also be very bad for children. Parents should interact with their babies and children. There should be a back and forth between the child and the parent with lots of eye contact. They should talk to them as though they are having a conversation.  How many words they hear as part of this conversation is important for their brain development. Each child needs to feel loved and liked to develop the self-confidence to navigate their world as they grow and develop.

Talking about gene-environment interactions (GxE), what do we know today in how far gene-environment interactions guide or influence specific behaviours in adults?
Marla Sokolowski: People thought it’s either genes or the environment; this idea is known as the nature-nurture dichotomy. And later this idea was shown not to be true, both genes and the environment are important. But it isn’t the case that they add together so this much of the child’s behaviour has to do with genes and this much has to do with environment. What we know now is that we have certain genetic predispositions that get modified by the environment (our experiences) and this affects our behaviour and. With certain genetic variants a child will be well buffered from later depression even though they experience neglect while with a different set of genetic variants the child is more vulnerable to depression if they experience neglect. When children with both types of genetics grow up in nurturing environments both are protected from developing depression. This is what we mean by GxE. Genetics can protect us or put us more at risk but it’s probabilistic so that’s how genes contribute to behaviour in a probabilistic way but it’s not fixed, it’s not determined.

Interventions or other kinds of experiences in life can help or reverse these risks. Nothing is in stone, there is no genetic blueprint that determines. Rather, some individuals depending on their genetics would be more likely to have problems later in life depending on their early environment.

Tom Boyce: Genes select and modify environments that they’re in and those environments modify the expression of the genes that the child has. The environment also can affect the expression of genes by epigenetic marks that calibrate and modify the expression of those genes over time. Both genes affect environment and environments affect genes.


Organizer of the Conference Marla Sokolowski, Professor at the University of Toronto, and Tom Boyce, Professor at the University of California, at the introduction.

How persistence are epigenetic effects of psychological trauma over following generations?
Marla Sokolowski: From a statistical point of view, there’s correlation across generations. It doesn’t have to be the actual epigenetic marks that are passed on but the knowledge of an experience and the dread that might go along with that is in some families passed on to the kids just through the stories that are told. That would be a kind of behavioural inheritance from one generation to the other. There is evidence in animals that fear being associated with a certain smell is passed on through epigenetic marks into the next generations. More research needs to be done in this area to understand how epigenetics might be involved in trauma over generations.

There’s the direct experience of that environment for the grandmother which contains the egg that will produce the mother and similarly the granddaughter. To say it’s epigenetically inherited without direct exposure to trauma you have to go to the fourth generation just to give you an idea of how hard the experiments are. For a male sperm it’s different because they’re always made so a lot of people are starting to investigate the possible inheritance of epigenetic marks through the male line now.

Are children who grow up in privileged environments better able to reach their potential in educational attainment and non-cognitive skills?
Marla Sokolowski: I don’t think privileged environments necessarily means there isn’t neglect or abuse. What we do know is there’s a socioeconomic gradient in health so the richer and the more privileged you have, you have better health avoiding ear infections, asthma, and improved literacy. And you have the luxury of not being stressed, not having parents that are terribly stressed, probably better education also.

Tom Boyce: We certainly know that disadvantaged environments influence outcomes, not only in childhood but throughout life.

Marla Sokolowski: Equity from the start is really important.

Tom Boyce: We also know that there are kids who grow up in very disadvantaged environments that actually do very well. There’s a lot of variation even though the overall trend is for kids growing up in wealth and advantage to have better educational attainments and better health and live longer and somewhat there are kids who grow up in impoverished environments who do just as well as those kids and there are kids who grow up in wealthy homes and communities that don’t do well at all. There’s a lot of variation around that trend of socioeconomic differences.

Marla Sokolowski: The individuals that do incredibly well growing up in adversity and poverty are particularly interesting to study, to try and understand what’s special or what’s different about them and the same for the ones who have all the opportunities and flounder.

What do we know about the influence of the parent-child relationship in terms of epigenetics?
Tom Boyce: It’s crucial. Absolutely crucial. Not that it’s the only relationship that influences development but it is the primary one, it’s the earliest one. It’s the one that begins during the intrauterine life. We know that kids growing up in two-parent families largely do better than kids growing up in one-parent families. So, you know there’s every reason to think that having two parents is better than one parent. So, it’s an absolutely crucial formative influence on early development.

Marla Sokolowski: From the epigenetics perspective, there is research that shows that attachment between parent and child giver is when you have strong attachment that happens early in life, the kids are better able to cope with future stresses as children and also into adulthood. There’s ways that scientists measure this difference and parental attachment with babies and mothers in a room and then the mother goes out, a stranger comes in and then the mother or the father (or caregiver) comes back in and you look at the behaviour of that child. Does the baby go to the mother get reassurance? Does the baby go forward and back and realize that they’re not going to get reassurance? Does the child look over and then start playing? This can be measured. It’s very important that that attachment is strong for an infant. And I think mostly they need one person for that. And if you have attachment that isn’t strong partly because the mother or father is not reliable, then the stress response system gets what we call dysregulated and it’s harder to cope with any future stress or trauma you might have.