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Men are biologically programmed to care for their children

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Men experiencing a decline in testosterone levels - the male hormone - after they become fathers, according to a study published Monday suggests that men whose conclusions would be so biologically programmed to care for their children.

The phenomenon can be observed in many other animal species whose males helps increase their successors, said Christopher Kuzawa, professor of anthropology at Northwestern University in the U.S. state of Illinois, one of the authors.

Virility and testosterone incentive males compete to mate. After the birth of offspring, males reduce the secretion of this hormone the body - and therefore sexual needs - to allow the male to assume his responsibilities to posterity, without being captured by 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 extends to very short periods, preventing researchers to know 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 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 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 constraints associated with the birth of the baby require a significant change in emotional, psychological and physical, and our study indicates that a man can experience a substantial biological change to help meet these requirements," said Lee Gettler.