We wish all Dads a Happy Father's Day :
How fathers are shaped by their children
Popular convention may dictate that
the father's role in the early development of his children pales in
comparison to the mother's, but author Paul Raeburn is shedding new
light on the science behind the vital contributions of the often
overlooked male parent.
During pregnancy, mothers experience a variety of profound hormonal
and physical changes that help to prepare them for the substantial task
of carrying and nurturing the foetus and new baby. That's not news; what
is news is that men also undergo hormonal turmoil.
One of the most obvious changes is the weight gain that many men
experience along with their wives during pregnancy. Many women
experience cravings and of course require more food during pregnancy.
The men's weight gain could be occurring simply because they are tempted
by all that extra food in the house. We don't need hormones to explain
that.
Anthropologists
have discovered that this phenomenon, called couvade (from the French
word meaning 'to hatch"'), occurs not only in Britain and the United
States but in non- Western societies, too, sometimes to an even more
extreme and incapacitating degree.
In Papua New Guinea, some men, while waiting for their babies to be
born, "retire to bed with unremitting nausea and incapacitating back
problems, demand to be looked after, and otherwise raise an emotional
fuss during the last months of their wives' pregnancies."
One of the key hormones that's affected is the sex hormone
testosterone. And the other is prolactin, a hormone involved in the
production of milk by nursing mothers. Men have prolactin, too, even
though they don't nurse children. Why its levels should change in men
has been a mystery.
Behavioural changes
We've known that hormonal changes occurred in some animal species in
which the fathers participated in rearing their offspring; prolactin
levels rise in primates, in male birds just before they become parents,
and in rodent species in which fathers help to care for their offspring.
But nobody had shown much interest in looking at human fathers, to see
whether something similar might be going on.
In a paper published in 2000, Anne E. Storey, Katherine E.
Wynne-Edwards, and their colleagues at Memorial University in
Newfoundland began their study by acknowledging that lack of research:
"Little is known about the physiological and behavioural changes that
expectant fathers undergo prior to the birth of their babies," they
wrote.
Based on the findings in animals, Storey and company predicted they
would find similar changes in male humans, beginning during their
partners' pregnancy and continuing after birth. And they predicted that
the variation in hormonal levels in any individual would be related to
men's symptoms during pregnancy and their responsiveness to their
infants.
They recruited thirty-four couples taking prenatal classes at a
nearby hospital and took blood samples from the men before and after the
births of their babies. All but three of the couples were first-time
parents. The couples were asked whether the men had experienced any of
the typical symptoms of pregnancy- nausea, weight gain, fatigue,
increased appetite, and emotional changes.
The couples who were tested were exposed to their newborns, or to
blankets that had been in the nursery, and to a film about
breast-feeding to see whether the infant cues would cause any short-
term change in hormone levels.
The tests revealed significant changes in each of the three hormones
Storey and Wynne-Edwards measured-testosterone, cortisol, and prolactin.
And the pattern in men was similar to what happens in pregnant women.
Men's testosterone levels fell 33 percent when they had their first
contact with their babies, compared to measurements taken near the end
of their wives' pregnancies.
What could explain this change in testosterone? Many scientists
believe that a rise in testosterone is associated with competitive
behaviour in animals and in men. The drop that occurs with the birth of
a baby might be nature's way of encouraging men to drop their fists, at
least temporarily, and nuzzle their babies.
Paternal care-giving
From an evolutionary perspective, this is smart. Competitiveness is
incompatible with nurturing. And men who are more bonded to their babies
are more likely to stick around and support them.
Indeed, in September 2013, James K. Rilling and his colleagues at
Emory University reported in the Proceedings of the National Academy of
Sciences that testosterone levels in the blood were inversely correlated
with paternal care-giving-that is, testosterone was highest in fathers
who devoted less effort to child care, and lowest in those who invested
more effort in child care. They also found that the fathers who devoted
more resources to their children had smaller testicles. The results
provide evidence for the supposition that there is a trade-off between
the effort devoted to mating and to parenting. Some males choose to
devote more effort to mating and less to child care; others choose the
opposite course.
(Excerpted from Do Fathers Matter? What Science Is Telling Us About
the Parent We've Overlooked, by Paul Raeburn -Scientific American/FSG,
2014) |