by Robert Garrett Rodriguez, Ph.D., M.P.H. M.S.
Did you know that women in the United States on average outlive men? Although this is sometimes thought to be a recent phenomenon, rooted in improvements in medicine that make childbearing less risky, Swedish mortality records going back to 1780, long before modern medicine, show that women lived on average 5 to 8 percent longer than did men.
In a study of ten primate species, including humans, apes, and various Old world and New World monkeys, researchers have shown that the parent that cares for the offspring typically lives longer than the mate, regardless of gender. And, the mother is not always the primary care giver!
The male Titi monkey of South America, for example, takes care of the baby after the mother has given birth, and outlives his mate by 20 percent. In contrast, female chimpanzees and orangutans who are the sole caregivers, live significantly longer than their male counterparts. In captivity, female chimpanzees live on average 42 percent longer than do males. In the world, three times more females than males are found in natural groups, reflecting their greater survival rates.
This pattern is reversed in such species as the Siamang Apes, who pair-bond. Siamang males are unique among apes in the intensity of their bonding with their offspring, who they carry from the second year on. Male Siamang apes live 9 percent longer than their female counterparts.
Researchers working in this area conclude that this gender-specific enhanced survival is the result of a complex blend of reduced risk taking and reduced vulnerability to stress, which may be mediated by the hormonal effects of parenting. Researchers find that testosterone levels are reduced during pregnancy for most male mammals, including humans. Former levels are restored during the postpartum period. In humans this usually takes three to six months.
Although there are exceptions to this by species and individual, prolactin, which is generally known as the hormone that stimulates milk production in new mothers, increases during this same period for males. It's believed that this may reduce male aggressiveness during pregnancy and produce the more nurturing attitude often seen in expectant and new fathers. (It may also be responsible for the soft, gentle manner of grandfathers since testosterone levels decrease and prolactin levels increase as men get older.) Prolactin is related to nesting and nurturing activity and is the reason male penguins and both male and female pigeons produce crop milk, a sort of "non dairy creamer" that nourishes their young.
Prolacin sometimes encourages nurturing behavior in new fathers, it rarely stimulates milk production in male mammals, but there are exceptions. In rare cases, when the milk-producing apparatus has been exposed to higher-than-normal levels of estrogen and progesterone, prolactin can stimulate milk production in males. A particular biologist describes the case of a Scottish goat named Claymore. Claymore was a remarkable goat with an extraordinarily high prolactin level. Being male didn't interfere with his ability to produce milk. In fact, he liked his own milk so much that he would sometimes nurse himself in the barnyard. He also provided enough milk for the production of goat milk cheese.
So nature provides us with a great lesson: there are few "norms" in what we otherwise consider normal. For many creatures, including us, fathers can and do assume a nurturing role. In the animal and insect examples presented, fathers are responsible for everything from being the recipient of courtship, to delivering the young and childcare. You may want to share some these examples with your male partner along with a low whisper in his ear, "You're such an animal!"