Fatherhood, pairbonding and testosterone in the Philippines

Area of Science:

• Evolutionary Anthropology
• Human Reproductive Endocrinology
• Behavioral Ecology

Background:

• Testosterone (T) is hypothesized to mediate the trade-off between parenting and mating effort in species with significant paternal care, such as humans.
• Previous studies show lower T levels in pairbonded men and fathers compared to single, non-fathers, but population variations exist.
• Understanding the role of T in human reproductive strategies requires examining diverse cultural contexts.

Purpose of the Study:

• To evaluate the hypothesis that testosterone mediates the trade-off between parenting and mating effort in a large, representative birth cohort of young men in Cebu City, Philippines.
• To investigate the association between pairbonding, fatherhood, and childcare involvement with testosterone levels.
• To explore potential cultural variations in the relationship between testosterone, pairbonding, and fatherhood.

Main Methods:

• Salivary bioavailable testosterone (T) was measured in 890 young men (age 20.5-22.5 years) upon waking and before bed.
• Plasma T and luteinizing hormone (LH) were measured in morning plasma samples.
• Men's pairbonding status (living with a partner or married), fatherhood, and self-reported childcare involvement were recorded.

Main Results:

• Pairbonded men exhibited significantly lower T levels at both times of day compared to single men.
• This association was entirely explained by fatherhood status; among non-fathers, pairbonded and single men had similar T levels.
• Increased childcare involvement correlated with lower evening T levels, and similar patterns were observed for plasma T and LH, suggesting central regulation.

Conclusions:

• Findings support the role of testosterone (T) in mediating the balance between mating and parenting effort in humans.
• Fatherhood status, rather than pairbonding alone, is a key factor associated with lower T levels in this population.
• The observed relationships, including modest T differences compared to other studies, suggest cultural variations in paternal involvement influence testosterone dynamics.