Gaia Vince in New Scientist:
Dads-to-be pile on the pounds during their partners’ pregnancy too – at least in some monkey species, new research suggests. The findings may illuminate the biological changes that occur in men to encourage effective fatherhood, since the primates studied are exceptionally good parents.
Pregnancy is something that not all expectant fathers miss out on – male “sympathetic pregnancies” have been reported in humans but never systematically studied. They are often regarded as psychosomatic events.
Now a US team has studied the parental weight patterns of common marmosets and cotton top tamarins – two squirrel-sized, monogamous primate species – from conception to birth. Each month the 25 prospective dads and 33 pregnant mums were weighed. The creatures’ food supply was maintained but not increased during the gestation periods for the marmosets (five months) and tamarins (six months).
“We found that the males gained on average an extra 10% of their body weight during the pregnancy,” says Toni Zeigler who led the research at the University of Wisconsin-Madison National Primate Research Center.