The Life of Dad

by Anna Machin

  So, contrary to the long-held belief that fatherhood is a learnt rather than biological phenomenon, the increasing evidence for the role of hormones in shaping men for fatherhood makes it clear that it is a truly biological business on a par with motherhood. From the synchronizing of oxytocin levels with your pregnant partner, to the drop in your testosterone levels following birth, to the interplay between oxytocin, dopamine and testosterone, evolution has made it its business to ensure that dads are biological beasts motivated to care, protect and provide. But while our knowledge of the neurochemistry of fatherhood is growing on an almost daily basis, the complexity of the genes that underlie a man’s unique cocktail of these vital chemicals, and the impact that his environment may have on their expression, is still largely shrouded in mystery.

  The debate as to how much of our individual behaviour is predetermined by our genes and how much is a result of experience has raged since Charles Darwin first laid eyes on a Galapagos finch and came up with the idea of evolution and Gregor Mendel answered his green-fingered calling and produced some lovely, colourful pea plants that seemed to be a mix of their parents. In the seventeenth century, English philosopher John Locke believed we were born a blank slate – a tabula rasa – and that our thoughts and behaviours were shaped purely by our experience, while those who believe in genetic determinism consider us to be on a journey dictated purely by our genes and that our life experience plays no part in determining our final destination. As is so often the case, the truth lies somewhere between these two extremes. As we develop better and better techniques for analysing the genetic code and learn more about the behaviours that are influenced by our genes, we are starting to understand a few key principles about the genetic influence on behaviour. Firstly, some genes have more of an influence on our behaviour than others. Between 40 per cent and 80 per cent of antisocial behaviour is genetically determined, while a 2015 study led by geneticist Brendan Zietsch argues that the risk of being unfaithful is 40 per cent down to your genes if you are a woman and 63 per cent if you are a man – a slightly scary thought. Secondly, some behaviours are influenced by more than one gene or more than one change on a single gene. In some cases, this leads to a ‘dose response’, where the greater number of ‘risk’ genes you carry – some genes have these and they are associated with negative behaviours – the more risk there is of the negative behaviour developing or the more extreme it becomes. Finally, there is the idea that in some cases nature and nurture exist within a feedback mechanism, where a risk gene will only result in a negative behaviour if a certain psychological state or life experience is present. So, carrying the risk gene alone will not cause the behaviour to occur – it will only be expressed if particular environmental conditions are present as well.

  The field of paternal genetics is very young. When we consider that fatherhood has really only been a focus for academic study for just over a decade, it is unsurprising that we have only just started to try to understand its genetic underpinnings – we have to have a solid understanding of behaviour and neurochemistry before we can start to unravel any genetic control of them. But one of the few studies that has been carried out reflects perfectly this intimate relationship between genetics and environment. In his analysis of the risk of serious and violent delinquency in African American teenage girls, sociologist Matt DeLisi, from Iowa State University in the US, studied the interaction between the dopamine receptor gene (DRD2), the presence of a criminal father and rates of recorded delinquency and police contact among the girls. DRD2 exists in a risk and non-risk form. Presence of the risk version is linked to a range of antisocial behaviours and addictions, including alcoholism and heroin dependency. In this case, DeLisi took DNA samples from the 232 girls and looked at the relationship between the presence of the risk version of the DRD2 gene and the likelihood that a girl would exhibit delinquent behaviour. What he found was that carrying this gene alone did not predict the likelihood of the girl exhibiting such behaviour – so, no evidence for genetic determinism here. But, if he also included in the analysis whether or not the biological father had a criminal record, then a pattern became clear. If the girl had a criminal father and she carried the risk version of the DRD2 gene, then she was significantly more likely to have had contact with the police due to violent and serious delinquency. The risk version of the gene was only making its presence felt in the girl’s behaviour if dad had a criminal record. The perfect example of the co-dependency that exists between nature and nurture.

  Similarly, children who carry the risk version of the dopamine transporter gene, DAT1, are only at increased risk of developing alcoholism if their biological father is, or has been, an alcoholic. Criminologist Jamie Vaske found, again, that when considering their impact independently neither the risk version of DAT1 nor having an alcoholic father increases their risk – the combination was key. However, in this case it did not seem to matter whether dad lived with their child or not, the impact of their alcoholism on those unfortunate enough to carry risky genes was the same. This would suggest that in this case the influence of the alcoholic father was not down to his impact on the child’s environment of development but was a result of genetic inheritance – remember, dad was the biological father. A gene or set of genes that the child had inherited from the alcoholic dad, when combined with the risky DAT1 gene, led to an increased chance of alcoholism – a genetic dose response. As alcoholism is thought to be highly heritable – genetics are believed to lie behind 40 to 60 per cent of cases – the interaction of several genetic factors to cause this outcome comes as no surprise.

  If we were to rely solely on the results of DeLisi and Vaske’s studies, we might conclude that all children inherit from their fathers are addictions and antisocial behaviours, but this is, thankfully, very unlikely to be the case. As the field of paternal genetics is young, studies that seek solutions to society’s problems are always going to get funded before those that seek to assess to what extent cuddling, coaching football or the ability to do a passable impression of a Teletubby is genetic. As time passes and the field grows, attention will shift to these more positive, and widespread, behaviours and we will start to discover all the wonderful traits that children inevitably inherit from their dads.

  While individual fathering behaviour is strongly influenced by the triple cocktail of oxytocin, testosterone and dopamine, a flood of these alone is not sufficient to produce a sensitive parent – we need to ensure that the other piece of the neural jigsaw is also present: the receptor. Brain receptors are like the locks into which the neurotransmitter key fits to enable its message to be transmitted around the brain. The nature of receptors can vary between individuals in both the number within an area and their affinity for the neurotransmitter – that is, how well the lock and key fit together and how efficiently the message is conveyed. The oxytocin receptor gene (OXTR) is highly variable, meaning that it comes in many different versions and, as such, is likely to be the cause of this variability in receptor density and efficiency. The OXTR gene has been implicated in a range of behaviours linked to our social experience. These include how adept we are at using affectionate language towards our lover, how likely we are to want to form a romantic relationship in the first place, how many friends we have and how much we enjoy being sociable. It has also been implicated in the quality of fathering behaviour. Alongside it sits another nattily named gene, CD38, which has a role in the production of oxytocin and also seems to influence how a father behaves when he is interacting with his baby.

  Both OXTR and CD38 have risk versions – remember this means they are linked to negative behaviours. These versions appear to be associated with deficits in social behaviour and the lower baseline levels of oxytocin that can make it difficult for the individual who carries them to form and maintain social relationships. Individuals who exhibit conditions that make it difficult for them to cope in social situations, such as autism, tend to carry risk versions of OXTR and CD38, and dads who carry them also seem to s
truggle with forming healthy and sensitive bonds with their children. Ruth Feldman and her team observed these difficulties in their study exploring the influence of the risk versions of CD38 and OXTR on fathers. Of the 121 fathers she studied, those who carried either one or both risk genes were less sensitive when interacting with their 6-month-old babies. When their interactions were observed, the team saw that these fathers were much less likely to touch their child affectionately and actively tried to avoid their baby’s gaze, meaning that the all-important bio-behavioural synchrony that kick-starts the parent-to-infant bond was lacking. Analysis of the father’s blood samples gave some idea why. Fathers who carried risk versions of the OXTR and CD38 genes had much lower levels of oxytocin – and, by association, dopamine – meaning that interacting with their baby was not the source of warm and rewarding feelings that it should have been. The neurochemical prompt to bond was just not there.

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  I mean, seeing my parents, they are both quite different, but seeing the friendship that I have with my parents, that is something I would like to have with Joseph. I expect him to say [frustrated], ‘Oh, dad,’ but, underlying that, I want to have the bigger kid sort of friendship relationship as well.

  John, dad to Joseph (six months)

  While genes quite clearly have a role to play in how we parent, one profound influence on our individual parenting styles is undoubtedly linked to our own experience of being parented. Early evidence of this came from a study that should win the authors a ‘most dedicated scientists of the century’ award. Over a period of twenty-eight years, developmental scientists Nikki Kovan, Alissa Chung and Alan Sroufe followed sixty-one families to try to understand to what extent the children of the families would mirror the parenting behaviours of their parents when they had children of their own. This meant videotaping interactions between parents and children when the children were two years old, then, having filled the intervening years with other academic activities such as drinking coffee and thinking, returning when the children had themselves become parents and their offspring were themselves two years old. Comparison of the two sets of videotapes suggested that there was a surprising degree of similarity between the parenting behaviours of the two sets of parents, as much as 43 per cent. This suggests that a significant fraction of our individual parenting behaviours is indeed inherited from our parents, but the question remains as to the exact nature of this inheritance – is it behavioural as a result of experience or genetic?

  Daniel Pérusse of Montreal University in Canada set out to try to untangle this tricky web using the genetic similarity between identical twins to help him. Twin studies are a godsend to science because they rely on the fact that siblings experience identical environments as they grow up but that identical twins carry identical sets of genes, whereas non-identical twins are as genetically related as any sibling pair. If a behaviour is genetically inherited, then we should see more mirroring of behaviour between identical twins than non-identical twins, as the identical twins have more genes in common. These studies allow us to infer a role for genes without going to the huge expense of having to extract and analyse everyone’s DNA, and this means we can study many more people, making our results more robust. Daniel studied the self-reported parenting behaviour of 1,117 twin pairs, all of whom had children. Of these, 675 pairs were identical; 169 male twin pairs and 506 female twin pairs. When comparing the parenting behaviours of the identical twins with the non-identical twins, he found that identical twins shared many more parenting behaviours in common, implying some genetic transmission of this behaviour. However, this similarity was stronger in female twin pairs, that is, mothers, than male twin pairs, that’s the dads. Daniel calculated that, based on his results, 19 per cent of fathering behaviours were under genetic control compared to 39 per cent in mothers.

  Nineteen per cent is a considerable amount of genetic control, and even more impressive when you consider how complex and extensive parenting behaviours can be – that is a lot of genes. It is amazing to think that nearly one fifth of fathering is biologically innate – that it is programmed into your genes. However, that leaves 81 per cent of the variation between individuals in fathering behaviour down to some other factor, and the number-one candidate is, inevitably, the environment – and not just any environment, but the environment in which you grew up.

  We know that the development of the oxytocin pathways in the brain of a young mammal are influenced by their experience of being parented. Infants that receive optimal maternal care have higher densities of oxytocin receptors in the areas of the brain linked to social behaviour, are better able to deal with stress and are better, more sensitive parents when they themselves have a family. It is likely that the same is true with us. It takes some time for our big brains to grow and a human baby’s brain continues to grow at a startlingly rapid rate for a year after birth. As such, the experiences that a human baby has of being parented during this period can have a profound effect on brain structure – hence the belief that the first 1,000 days of a child’s life, that’s conception to two years, are the most fundamental to their healthy development. If a child receives sensitive parenting from mum and dad during this period – a style that is nurturing but not intrusive, protective but not controlling – then he or she should develop a healthy brain and a strong and secure attachment both now and in any future relationships.

  One way to achieve this goal is to encourage synchronous behaviours between baby and parent – to mirror each other through body language, speech, sound and emotion. This means sharing gaze, mirroring body language, responding to invitations to speak or play and being alive to baby’s emotions and needs. If a parent can achieve this, then the bio-behavioural mechanism will kick in – remember this is the mechanism by which parents achieve synchrony in oxytocin levels during pregnancy, leading to a strengthened bond. Likewise, baby and dad will achieve emotional, physiological and hormonal synchrony and, ultimately, a strong and healthy attachment between baby and parent will develop. It goes without saying that the originator of this hypothesis, Ruth Feldman, has tested it. In her long-term study of sixty Israeli families, she has shown that there is a significant positive relationship between a child’s baseline oxytocin level when they are three years old and that of his or her parents. This suggests that the synchrony in behaviour and physiology – heart rate, blood pressure and body temperature – does result in a synchrony in hormone levels.

  And amazingly, this synchronous effect is achievable in a time period counted in minutes rather than years. Omri Weisman and Orna Zagoory-Sharon explored the impact of artificial oxytocin on the fathering behaviour of thirty-five fathers towards their 5-month-old babies. Oxytocin is one of the few neurochemicals we can manufacture in a lab and, as a result, we can use it to induce bonding behaviours experimentally. In this case, Omri and Orna asked fathers to squirt a dose of either synthetic oxytocin or a placebo – dads didn’t know what they were getting – up their nose. This enables the oxytocin to cross from the bloodstream into the brain via the most straightforward route. They then observed the dads interacting with their babies. What they found was that those dads who had received a dose of synthetic oxytocin showed more sensitive and synchronous interactions with their babies. However, the more exciting finding was that despite not having anything squirted up their own noses, the babies’ oxytocin levels had also risen in parallel with their dads’ – bio-behavioural synchrony in action.

  And all dads can work towards achieving this important effect without the aid of a squirt up the nose. I am often asked what the most important things are that a parent can do for their child. I always respond that beyond the need for practical care, the most important thing any parent can do is spend focused, physically close time with their child. Get eye contact, enter into a ‘conversation’ with sounds or words, take part in reciprocal interactions, shower them with affectionate touch and take the time to tune into their emotional needs so that you respond suitably. If you can
do this, and it need only be for five minutes at a time, you are providing your baby with the firm foundations of a secure attachment – and a functioning oxytocin and dopamine system – with which they can go forward and successfully confront life, with all its challenges and rewards.

  This close link between parenting style and the development of oxytocin levels in babies also means that the secure bond you develop with your baby has the potential to cross generations. A father’s attachment to his own parents has a significant impact on both his baseline oxytocin levels and the sensitivity with which he parents his own child. Dads who perceive their relationship with their parents to be warm and secure have significantly higher oxytocin levels and are more sensitive to their child’s needs than fathers who, in contrast, have experienced overly controlling or neglectful childhoods. The environment of a father’s upbringing has a profound and very real influence on the way he parents his own children. Parents who have high baseline oxytocin are motivated to practise sensitive parenting, which, in turn, leads to high baseline oxytocin in their offspring, who, in turn, become sensitive parents themselves, and so the cycle continues.