Rapid weight gain after birth predicts life history and reproductive strategy in Filipino males

PNAS recently came out with an article based on a longitudinal study of 770 Filipino males. The authors, Christopher Kuzawa et al, found that rapid weight gain after birth could predict “male life history characteristics, including maturational timing, reproductive hormones, adult size, strength, and sexual activity.”

Since this article is not open access, so we have to make do with what PNAS provides us with: an abstract of Kuzawa’s article.

Ecological cues during prenatal and postnatal development may allow organisms to adjust reproductive strategy. The hypothalamic-pituitary-gonadal (HPG) axis is a prime candidate for adaptive plasticity as a result of its critical period of birth to 6 mo (B6M) in humans and the role of testosterone in the development and maintenance of costly sexually dimorphic somatic and behavioral traits. We hypothesized that weight velocity specific to B6M would predict male life history characteristics, including maturational timing, reproductive hormones, adult size, strength, and sexual activity. Data come from 770 Filipino men (age 20.5–22.5 y) followed since birth, with predictor variables including birth weight and weight velocities calculated at 6-mo intervals during the first 2 y of life. As expected, infants who were breastfed experienced less diarrhea, lived in wealthier households with better hygiene, and grew faster from B6M. Males with rapid B6M growth reached puberty earlier and, as young adults, had higher testosterone levels, were taller, more muscular, and had higher grip strength. They also had sex earlier and were more likely to report having had sex in the past month, resulting in more lifetime sex partners. Relationships between B6M weight gain and physical outcomes were generally not present or weaker in female subjects. We conclude that rapid weight gain specific to the brief postnatal hypothalamic-pituitary-gonadal critical period predicts early maturation and sexual activity, elevated hormone production, and more costly adult somatic characteristics among the male subjects in this sample. These findings provide evidence for early life developmental plasticity in male life history and reproductive strategy in humans.

Also, I reckon that the longitudinal data used in this study were from the University of San Carlos Office of Population Studies (USC-OPS), a research institution established by Fr. Wilhelm Flieger, SVD . Flieger, who passed away in 1999, was one of the pioneers of demography in the Philippines. A major project he spearheaded was the Cebu Longitudinal Health and Nutrition Survey and the Early Childhood Development Project Evaluation Study conducted in 1983 whose initial aim was to monitor the general health and nutrition of selected infants. Since then, the collection of data for this longitudinal study continued and studies spun off to several directions–from the biomedical field to psychosocial and anthropological researches.

To know more about the University of San Carlos’ Office of Population Studies, please click here.

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