The First Ejaculation: A Male Pubertal Milestone Comparable to Menarche?

Earlier sexual debut predicts higher (not lower) levels of father care measured across 12 weeks: an experience sampling study

Across the lifespan, males negotiate the tradeoff between current and future reproduction. From a life history theory (LHT) perspective, resources invested into earlier reproduction pose a cost to later reproduction. The age of sexual debut is a commonplace measure of sexual maturation. However, in males, thorarche (age of first ejaculation) and years from thorarche to age of first reproduction both represent milestones related to reproductive timing. A fundamental prediction from LHT is that earlier sexual maturation-a "quantity" strategy-predicts decreased levels of care per offspring. In the current study, we test this straightforward relationship looking specifically at a father's investment of time. In a sample of first-time fathers, we measured the amount of time spent with their 9-to-12-month infants longitudinally using an experience sampling method (ESM)-an ecologically valid method of collecting self-report data on fathers' use of time Fathers contributed data on their time allocation across a 12-week period. They reported on ages of sexual debut, thorarche, and the years between thorarche and first reproduction (i.e., current age) was calculated. Only age of sexual debut had a relationship with time allocated toward infants. Importantly however, this effect was in a direction opposite of our LHT derived hypothesis. Males with earlier sexual debut spent more time with their infants. Discussion focuses on the potential contributions to this finding and limitations related to small effect size, methods and measurement, and sample demographics.

Father absence and pubertal timing in Korean boys and girls

Background and objectives

Pubertal timing is a key life history trait with long-term health consequences in both sexes. Evolutionary theory has guided extensive research on developmental influences, in particular growing up without a father, on earlier menarche. Far less is known whether a similar relationship exists for boys, especially beyond western contexts. We used longitudinal data from the nationally representative sample of Korean adolescents, which provided us with a unique opportunity for studying male puberty using a hitherto underutilized biomarker: age at first nocturnal ejaculation.

Methodology

We pre-registered and tested a prediction that growing up in father-absent households is associated with earlier puberty in both sexes. Large sample size (>6000) allowed testing the effect of father absence, which remains relatively uncommon in Korea, while adjusting for potential confounders using Cox proportional-hazard models.

Results

Self-reported age at first nocturnal ejaculation was on average 13.8 years, falling within the range known from other societies. Unlike previous findings mostly for white girls, we did not find evidence that Korean girls in father-absent households had a younger age at menarche. Boys in father-absent households reported having their first nocturnal ejaculation 3 months earlier on average, and the difference was evident before age 14.

Conclusion and implications

The association between father absence and pubertal timing appears sex- and age-dependent, and these differences may further interact with cultural norms regarding gender roles. Our study also highlights the utility of the recalled age of first ejaculation for male puberty research, which has lagged in both evolutionary biology and medicine.

Trauma during Early Adolescence and Boys' Social Behavior: A Focus on Teen Dating Violence

Although early adolescence is increasingly recognized as commencing a sensitive period for social development, little research exists on the impact of trauma exposure during this juncture. We hypothesized that trauma experienced during early adolescence would be particularly disruptive to the acquisition of social skills necessary for healthy future relationships. Among 1500 boys from the National Comorbidity Study Adolescent Supplement, we examined trauma exposure across developmental periods on interpersonal outcomes in late adolescence. Most (62.3%) participants reported prior exposure to at least one potentially traumatic event, and rates of such exposures generally increased linearly over time with a relative spike in exposure occurring at age 15. Trauma exposure during early adolescence, but not other developmental periods, uniquely predicted boys' perpetration of physical teen dating violence (TDV; OR = 2.2) and broader social problems (B = 2.061, SE = .091) in late adolescence. In contrast, and consistent with existing literature, trauma exposure early in development and during mid-adolescence predicted late adolescence conduct disorder diagnoses. At least in the context of early adolescent exposure, the link between trauma and TDV perpetration may be conceptualized within a broader framework of social competence rather than oft-purported antisociality. Early adolescence may present opportunities for targeted prevention of TDV and broader social problems.