It seems it’s not just women who are biologically wired to nurture
their babies — fathers also go through hormonal changes to help them
care for their children.
In many species of mammal the male
takes a major role in caring for offspring and now new research points
to humans having the same capability.
A new study has found that
upon becoming a father a man’s testosterone levels decrease. While
testosterone helps the males of species compete for a mate it is not
necessarily conducive to fatherhood, hence the reduction in levels.
Although
previous studies have pointed to this phenomenon they have been too
small to be conclusive and have not identified whether fatherhood
reduced testosterone levels or whether men with lower levels of
testosterone were more likely to become fathers.
But this study
carried out by scientists at Northwestern University in Chicago, US and
the Office of Population Studies Foundation in the Philippines followed
a group of 624 men in the Philippines, aged between 21 and 26 years
old, for more than four years. None were fathers to start with so the
changes in their testosterone levels on becoming a father could be
measured.
The researchers found that men with higher levels of
testosterone were more likely to become fathers but once they had their
levels dropped substantially. “Our findings suggest that this is
especially true for fathers who become the most involved with child
care,” said Lee Gettler, an anthropologist and co-author of the study.
The
emotional and physical changes a new father goes through can be
significant and the study found that fathers often go through a very
large, but temporary, dip in testosterone when they first bring home
their newborn baby. “Our study indicates that a man’s biology can
change substantially to help meet those demands,” said Gettler.
And
there appears to be another interesting side-effect to these results
which may explain why single men often have poorer health than married
men and fathers. The lower testosterone levels may help protect the men
against some chronic diseases as they age.
“Humans are unusual
among mammals in that our offspring are dependent upon older
individuals for feeding and protection for more than a decade,” said
Christopher Kuzawa, co-author of the study and associate professor of
anthropology in the Weinberg College of Arts and Sciences, and faculty
fellow at the Institute for Policy Research at Northwestern. “Raising
human offspring is such an effort that it is cooperative by necessity,
and our study shows that human fathers are biologically wired to help
with the job.”
