A recent study published in Human Nature sheds light on parental investment by birth fathers and stepfathers. The findings indicate that while birth fathers are typically the most involved in childrearing, the amount of time that a stepfather lives with a child can make a big difference in how much they invest in the child’s life. The research suggests that childhood co-residence plays a key role in paternal relationships.
The authors of the study aimed to better understand why stepfathers invest in children who aren’t biologically theirs. From an evolutionary perspective, there’s a bit of a puzzle. While investing in biological children directly benefits one’s own genetic lineage, investing in stepchildren does not. One theory suggests that stepfathers might invest more in their relationship with the child’s mother than in the child itself.
However, recent research shows that stepfathers can indeed form strong bonds and invest in their stepchildren, both when they are young and even after they become adults. In this study, the researchers want to understand how both birth fathers and stepfathers invest in their children and what factors play a role in this investment.
“I think parental investment and parental care are the most important behaviors to study to understand humans as a species,” said study author Jenni Pettay, a senior researcher at the University of Turku. “While step-parenting exists in some other animal species, it is very rare. However, step-parenting is quite common in humans and extends beyond the juvenile period. While the evolutionary reason for step-parental care is likely mating effort, i.e. pleasing the mate, it is also obvious that genuine attachment often happens between stepparent and stepchild.”
“I wanted to test the hypothesis that co-residency during childhood affects the quality of step-parenthood. In other words, the idea that living together during childhood forms a relationship that is more similar to that between biological kin. There are a fair amount studies on how current co-residence between (step)fathers and children affect their relationship, but not how it is related to their relationship later in life.”
For their new study, the researchers analyzed data from the Panel Analysis of Intimate Relationships and Family Dynamics (pairfam), a study examining intergenerational relations, childbearing, and socioecological factors in Germany. This longitudinal data, spanning three birth cohorts from 1971-1993, was chosen primarily for the wave 2 cross-sectional data (2010-2011) which captured the essence of childhood living arrangements and intergenerational ties.
At the heart of the study were parental investment variables derived from the pairfam questionnaire. These variables encompassed diverse dimensions of parental involvement, ranging from tangible support like financial and practical help, to more intangible metrics like intimacy, emotional support, and emotional closeness.
Additional variables were factored into the study, including the respondents’ gender, birth cohort, ethnicity, educational background, cohabitation status, childbearing, travel time to their parent’s residence, and current living status with the mother.
In line with evolutionary theories, the researchers found that birth fathers, even those separated from the child’s mother, showed more parental investment than stepfathers. However, the longer a child lived with their birth father or stepfather, the more the father invested in the child.
In other words, if birth fathers or stepfathers lived with their kids for longer, they generally invested more in them, both emotionally and financially. This was true even if the birth father had separated from the child’s mother. This suggests that forming close bonds through living together is crucial for both birth fathers and stepfathers.
“Fathers who were living with the mother were closest and gave more support than divorced fathers or stepfathers,” Pettay told PsyPost. “However, stepfathers and those fathers who were not living with the mother gave more support and were closer with the adolescent and adult child the longer these fathers had lived with child during their childhood. Childhood co-residence thus can have an important role in forming a personal bond between (step)father and child that extends into adulthood.”
While birth fathers usually live with their kids from birth, stepfathers often come into the picture when the child is older, sometimes even when they’re adults. But the study found that living together positively affected parental investment for both separated birth fathers and stepfathers. Interestingly, the length of time living with the child had a more profound impact on stepfathers than on birth fathers who were separated from the mother.
“It was perhaps a bit surprising that also divorced fathers’ support and emotional closeness correlated with childhood co-residence duration. Our hypothesis was that co-residency in childhood would not be as important for birth fathers as for stepfathers,” Pettay said.
Overall, the findings suggest that both nature (biological connections) and nurture (living together) play essential roles in father-child dynamics. The bond between stepfathers and stepchildren can be particularly influenced by how early and how long they live together. But the study, like all research, includes some limitations.
“One of the caveats of this study is that we did not know number of potential siblings or half-siblings for these adult children or if the step-fathers had other children from previous relationships, because these factors potentially have impact on their (step)father support,” Pettay explained.
“I would be very interested to know if length of childhood co-residence with stepchild relates to support to step-child also in the case that step-fathers relationship with the mother ends. I also think that changes in social roles of fathers and stepfathers is also interesting question.”
The study, “Parental Investment by Birth Fathers and Stepfathers Roles of Mating Effort and Childhood Co-residence Duration“, was authored by Jenni E. Pettay, Mirkka Danielsbacka, Samuli Helle, Gretchen Perry, Martin Daly, and Antti O. Tanskanen.
