Testosterone and Fatherhood – The Biology of Building a Family

Testosterone is the primary human male reproductive hormone; it promotes the development of reproductive tissues and confers secondary sexual characteristics, such as increased muscle and bone mass and increased body hair. New research suggests that testosterone levels are also correlated to fatherhood.

Several studies have revealed that men in committed, romantic relationships have lower testosterone levels that their single counterparts. Fathers — particularly those involved in care-giving — have even lower levels of testosterone. Most of these studies, however, were cross-sectional designs and it was impossible to determine if lower testosterone levels made men more likely to become romantically involved with a partner and father children or if testosterone levels changed with partnership and fatherhood. New research, published in the Proceedings of the National Academy of Sciences, suggests that the latter is true.

Investigators followed more than 600 men in the Philippines for 5 years. All of the men were single and had no offspring in the beginning of the study. Testosterone levels were evaluated at the beginning and end of the study. During the 5-year study period, approximately one-third of the men entered into committed relationships and fathered children. Men with the highest levels of testosterone were more likely to find a mate, and the new fathers had significantly lower testosterone that their single, non-father peers. Fathers who reported at least 3 hours of daily childcare had the lowest testosterone levels.

High testosterone levels are associated with mating, primarily male-male competition and mate-seeking behavior, a finding that was reinforced in the current study. Biologically, testosterone is needed to ensure mating and reproductive success. But, high testosterone levels are also associated with aggression, as well as an increased risk of prostate and testicular cancer, stroke, heart disease, and cognitive decline. So, testosterone may actually be damaging to success in fatherhood. The authors of the new study hypothesize that care-giving in a committed relationship and in fatherhood requires emotional, psychological, and physical adjustments, and male biology compensates for the changes by lowering testosterone levels. Such changes in male physiology benefit men’s health and care-giving abilities, leading to a long, fulfilling family life.

Evolution has granted men the ability to move from mate-seeking hunter-gatherers to care-giving partners and fathers. It is not clear if this new research will help men become better romantic partners or fathers, or if it is simply an interesting anthropological finding that helps humans appreciate why we are not as primitive as our evolutionary ancestors. Now, all we know is that any man with enough testosterone can find a mate and be a father, but it takes a lot less testosterone to be a family-man.

References

Burnham TC, Chapman JF, Gray PB, McIntyre MH, Lipson SF, & Ellison PT (2003). Men in committed, romantic relationships have lower testosterone. Hormones and behavior, 44 (2), 119-22 PMID: 13129483

Gettler LT, McDade TW, Agustin SS, & Kuzawa CW (2011). Short-term changes in fathers’ hormones during father-child play: Impacts of paternal attitudes and experience. Hormones and behavior PMID: 21889939

Gettler LT, McDade TW, Feranil AB, & Kuzawa CW (2011). Longitudinal evidence that fatherhood decreases testosterone in human males. Proceedings of the National Academy of Sciences of the United States of America, 108 (39), 16194-9 PMID: 21911391

Gray PB, Parkin JC, & Samms-Vaughan ME (2007). Hormonal correlates of human paternal interactions: a hospital-based investigation in urban Jamaica. Hormones and behavior, 52 (4), 499-507 PMID: 17716675

Gray PB, Yang CF, & Pope HG Jr (2006). Fathers have lower salivary testosterone levels than unmarried men and married non-fathers in Beijing, China. Proceedings. Biological sciences / The Royal Society, 273 (1584), 333-9 PMID: 16543176

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