Men are experiencing a decline in testosterone levels – the male hormone – after they become fathers, according to a study published Monday suggesting that men would be biologically programmed to care for their children.
The phenomenon can be observed in many other animal species whose males helps raise their successors, said Christopher Kuzawa, professor of anthropology at Northwestern University in the U.S. state of Illinois, one of the authors.
The testosterone stimulates the virility of males competing with other males to mate. After the birth of the offspring, males reduce the secretion of this hormone in the body – and therefore sexual needs – to allow the male to assume his responsibilities toward the children, decreasing the focus on that fight for mating, said Christopher Kuzawa.
Previous studies have indicated the presence of lower concentrations of testosterone in men who were parents compared to those without children.
But most of these studies extended to very short periods, preventing researchers to find out if paternity leads to lower testosterone levels or whether men with lower testosterone levels were more likely to procreate.
For this new study, the authors monitored 624 men aged between 21-26 years, for a period of four years in the Philippines.
During this period, approximately one third of the participants began a relationship with a partner and became fathers for the first time.
“Men who, at the baseline, had high levels of testosterone were more likely to become fathers in comparison with others, but after they procreated, the concentration of this hormone decreased significantly in their case”, said Lee Gettler, from Northwestern University, another author of the study, published in Proceedings of the National Academy of Sciences (PNAS).
“Being a father and the constraints associated with the birth of the baby require a significant emotional, psychological and physical change, and our study indicates that a man can experience a substantial biological change to help meet these requirements”, said Lee Gettler.