A father’s brain and biology change when he cares for his baby – in humans, marmosets and voles

A father’s brain is shaped much more by extent to which he is engaged in caring, or has been in the past: the more/less he cares, the more/less his brain changes.

A recent review of research details how changes in fathers’ brains and biology have been studied not just in human beings, but also in other mammal species where fathers are involved in the care of their offspring, including primates (various lemurs, New World marmoset, tamarin, titi monkey and owl monkey) and rodents (prairie vole, mandarin vole, degu, Californian mouse, Campbell’s dwarf hamster and Mongolian gerbil). Some patterns of change in the brain and biology of fathers can be seen across all these species, and some are unique to humans.

In just under 5% of species, mothers and fathers collaborate in the care of their young. Among monogamous species, the proportion practising biparental care is much higher, at 59%. In some species, fathers either contribute to care directly or, as in the case of titi monkeys and marmosets, are even the primary carers. In other species, fathers’ contributions are less direct. For example, they may be provide protection for the young.

Despite the matricentric view of parenting in Western civilisation, human infants across many societies have typically been raised in a collaborative effort between mothers and others (termed “alloparents”). Human fathers are variously involved in both direct and indirect care (e.g., controlling resources, protecting social status and setting the physical conditions for the family).

Compared to mothers’, fathers’ involvement in caring is much more diverse both between and within species. Extreme diversity is a particularly prominent characteristic of human fatherhood. Such diversity is reflected in the father’s brain, which is highly plastic in both humans and mammals. A father’s brain is shaped much more by the extent to which he is engaged in caring, or has been in the past: the more or less he cares for his young, the more or less his brain changes. The father’s proximity to the mother and the young also has an influence on his brain.

Along with changes in the brain, the experience of caring stimulates changes in fathers’ biology—for example, hormonal changes that are similar to those mothers undergo, involving oxytocin, prolactin, glucocorticoids, oestrogen, arginine, vasopressin and testosterone. The more active the father is in caring, the greater the hormonal changes. For example, prolactin increases and testosterone and cortisol drop more in marmoset monkeys who carry their infant more often. In humans and in cotton-top tamarins, hormone levels start to synchronise between mother and father when they actively care together.

Neuroscience shows that a common set of brain changes is associated with active fatherhood across mammals. But humans show additional complexity, involving parts of the brain that have evolved in humans but not in other mammals. Multiple changes take place in a human father’s brain and these coalesce into a “global human caregiving network”. The same thing happens in human mothers, and this helps human parents empathize with their baby’s feelings, respond to their baby’s emotions, express sensitive caregiving, understand non-verbal signals and engage in multitasking and planning.

Differences in brain function related to caring among human mothers and fathers appear to be linked to their roles in caring more than to ‘hard wiring’. Mothers show more activation in the amygdala, a more ancient part of the brain linked to instinctive responses. Fathers show more activation in the more recent cortical regions of the brain, associated with cognitive processing. However, the more that fathers care for their children, the more activation of their amygdala occurs, to the point that the brain of a primary caregiving father is similar in this respect to that of a primary caregiving mother. Meanwhile, the greater activation of the cortical regions of the brain remains higher in fathers than mothers however much the father is involved in caring. The more a father cares for his children, the more the connection grows between activity in the amygdala and activity in the cortical region of his brain.

Impact of brain changes in the parent on child development

It has been hypothesised that when a father and infant interact, they are activating the same areas of each other’s brains. This has led to the idea that an absence of fathering is a deprivation for the infant, leading to a lack of influence on the child’s brain that results in reduced motivation and social functioning, increased response to stress and anxiety and, finally, less involvement in parenting by the next generation. All this applies to mammals as well as humans. For example, in mandarin voles, paternal deprivation reduces parental behavior in both male and female offspring. Mongolian gerbil fathers reared without a father display lower parental responsiveness – they are less present and groom their pups less.

This intergenerational transmission is likely to involve altered gene regulation, or epigenetic change, that is inheritable—shown by the fact that, even in species where the father is not involved at all in caring, his experiences prior to mating influence the functioning of his offspring. Laboratory rats’ exposure to alcohol or stress, for example, modifies neurodevelopment in their offspring and their offspring’ offspring.

This research has important implications for absent or abusive fathering in humans. New understandings of neurobiology and biology may help develop better ways to break the cycle of poor fathering in human families. A better understanding of the brain and biology of human fathers should help us learn how to better mitigate the negative effects on children of poor or absent fathering. It could also help to understand how active fatherhood could mitigate the negative effects of poor maternal care.

The reviewers also ask an important question about fatherhood across cultures. How are these brain and biological processes – which are universal human characteristics – influenced by different cultures (for example, nuclear v. extended family living, patriarchal v. egalitarian systems)? What are the implications of this science for cultures where the caring role of men is highly limited?