Read Online Do Fathers Matter?: What Science Is Telling Us About the Parent We've Overlooked by Paul Raeburn - Free Book Online
Authors: Paul Raeburn
Ads: Link
Harvard’s Museum of Comparative Zoology, visitors must walk through the museum exhibits and past the famous Blaschka glass flowers. Haig has no laboratory. His job is not to do experiments, but to try to explain the results of others’ lab work. His greatest experimental achievement, early in his career, involved counting “a quarter of a million bristles on fly bellies,” he said, and that was enough to drive him out of the laboratory for good.
As his research led him beyond the study of plants, Haig began to explore the curious competition that occurs between parents and their offspring. In 1993, Haig published a paper on one aspect of the competition—a conflict that occurs between the mother and the fetus during pregnancy. Fathers might have reasons to compete with mothers, too, but Haig showed that a fetus does so even while utterly dependent upon her for survival. “Pregnancy has commonly been viewed as a cooperative interaction between a mother and her fetus,” he wrote. But that’s not true. It’s warfare in which “fetal actions are opposed by maternal countermeasures.”
One rather remarkable example of this is the ability of the fetus to alter its mother’s arteries so they can’t constrict. The fetus can then harvest whatever nutrients it wants from the mother’s bloodstream, through the placenta. And she is powerless to resist. That control also means that the fetus can release hormones directly into the mother’s bloodstream. One such hormone alters the mother’s regulation of insulin. The fetus can make its mother’s blood sugar rise. As that sugar-rich blood circulates through the placenta, it delivers more sugar to the fetus. But if the process goes too far—if the mother loses too much control over her blood sugar—the mother can develop diabetes, as was the case with James’s mom, Barbara. According to Haig, gestational diabetes is just one possible outcome of the survival struggle between mother and fetus.
Other hormones are believed to increase the mother’s blood pressure, enhancing the flow of blood to the fetus. If these fetal hormones overwhelm the mother, she can develop dangerously high blood pressure. This, too, is seen in the clinic. The condition is called preeclampsia, and when it occurs, blood pressure can climb to a level at which it becomes fatal. Haig marvels at these delicate relationships. “Natural selection produces things on this planet that are much more complex than any nonliving part of the universe. I come out of evolutionary biology, and I’m wanting to address this question—why has this thing evolved?”
As he was trying to work that out, he began thinking about another kind of genetic conflict, not between parent and child, but between parent and parent. It was an outgrowth of the work of Surani and Solter and others. He knew that they had found there was something that differentiated mothers’ genes from fathers’ genes. Haig was trying to explain why that is the case.
The result was his kinship theory. In broad terms, it goes something like this: Fathers and mothers both have strong interests in seeing their offspring survive. But they want different things for their children, because their reproductive strategies differ. In most mammals, the male is unlikely to mate with a given female more than once. He mates, moves on, and mates again. He doesn’t care whether that leaves her too depleted to have further offspring. They’re not his. Females, on the other hand, pursue the opposite strategy. Each of her young ties up a female for a good portion of her reproductive life. She is unable to mate as often and have as many children as a male, so she has to make sure that all her offspring survive. It’s a case of quality over quantity. With any given pregnancy, her strategy is to give the embryo what it needs, but no more. That conserves her resources for her subsequent children. Expending too many resources on one offspring might leave her
As his research led him beyond the study of plants, Haig began to explore the curious competition that occurs between parents and their offspring. In 1993, Haig published a paper on one aspect of the competition—a conflict that occurs between the mother and the fetus during pregnancy. Fathers might have reasons to compete with mothers, too, but Haig showed that a fetus does so even while utterly dependent upon her for survival. “Pregnancy has commonly been viewed as a cooperative interaction between a mother and her fetus,” he wrote. But that’s not true. It’s warfare in which “fetal actions are opposed by maternal countermeasures.”
One rather remarkable example of this is the ability of the fetus to alter its mother’s arteries so they can’t constrict. The fetus can then harvest whatever nutrients it wants from the mother’s bloodstream, through the placenta. And she is powerless to resist. That control also means that the fetus can release hormones directly into the mother’s bloodstream. One such hormone alters the mother’s regulation of insulin. The fetus can make its mother’s blood sugar rise. As that sugar-rich blood circulates through the placenta, it delivers more sugar to the fetus. But if the process goes too far—if the mother loses too much control over her blood sugar—the mother can develop diabetes, as was the case with James’s mom, Barbara. According to Haig, gestational diabetes is just one possible outcome of the survival struggle between mother and fetus.
Other hormones are believed to increase the mother’s blood pressure, enhancing the flow of blood to the fetus. If these fetal hormones overwhelm the mother, she can develop dangerously high blood pressure. This, too, is seen in the clinic. The condition is called preeclampsia, and when it occurs, blood pressure can climb to a level at which it becomes fatal. Haig marvels at these delicate relationships. “Natural selection produces things on this planet that are much more complex than any nonliving part of the universe. I come out of evolutionary biology, and I’m wanting to address this question—why has this thing evolved?”
As he was trying to work that out, he began thinking about another kind of genetic conflict, not between parent and child, but between parent and parent. It was an outgrowth of the work of Surani and Solter and others. He knew that they had found there was something that differentiated mothers’ genes from fathers’ genes. Haig was trying to explain why that is the case.
The result was his kinship theory. In broad terms, it goes something like this: Fathers and mothers both have strong interests in seeing their offspring survive. But they want different things for their children, because their reproductive strategies differ. In most mammals, the male is unlikely to mate with a given female more than once. He mates, moves on, and mates again. He doesn’t care whether that leaves her too depleted to have further offspring. They’re not his. Females, on the other hand, pursue the opposite strategy. Each of her young ties up a female for a good portion of her reproductive life. She is unable to mate as often and have as many children as a male, so she has to make sure that all her offspring survive. It’s a case of quality over quantity. With any given pregnancy, her strategy is to give the embryo what it needs, but no more. That conserves her resources for her subsequent children. Expending too many resources on one offspring might leave her
Similar Books
