Low testosterone sometimes makes men take care of their children and not so much courting new sexual partners. Researchers have now found that fathers’ active involvement has an impact on their sons’ testosterone levels.

Testosterone is the most important male sex hormone. Research has shown that when men become fathers and also take care of their children, their testosterone levels drop. A new long-term study now suggests that fathers’ behavior could have an impact on their sons’ testosterone levels. New fathers have lower testosterone levels when their fathers took care of them when they were young, a research group from the University of Notre Dame in Indiana shows with their study.

The researchers interviewed families between 1983 and 2014 and followed them from infancy to adulthood. The adult testosterone level of the 966 Filipino boys was determined using saliva samples. In the study, the research team examined how the father’s presence during infancy, childhood and adolescence affected their sons’ testosterone levels. The test subjects had in the meantime had children of their own.

The result: If the sons had a father who actively looked after them when they were young, their testosterone levels were lower when they became fathers themselves. How much time fathers had with their sons in infancy and middle childhood does not seem to have any impact. The result was also independent of the upbringing style and partnership relationship of the sons as fathers.

Genetics could also play a role

The researchers explain this effect by saying that the social relationship between father and son in adolescence changes the hypothalamus-pituitary axis. This part of the brain regulates the production of the hormone testosterone. “To me, this shows how parenting, and fatherhood in particular, can have lasting effects across generations, not just through behavior but also through biology,” study author Lee Gettler told Spectrum.

What the research team did not collect in the study, however, is the testosterone level of the fathers. But genes could also play a role. First-generation fathers may have taken better care of their sons when they had lower testosterone levels. Then the low testosterone values ​​of the sons could be explained by the genes. However, the researchers do not assume that an explanation for their results can be found in the genes alone. If there were a purely genetic effect, it would affect father behavior at all ages and not just in adolescence.

Sources: PNAS study, spectrum