Stress Gives You Daughters, Sons Make You Liberal

Dalton Conley in Nautilus:

In 1973, Robert Trivers and Dan Willard put forth the hypothesis that the sex of offspring is not, in fact, a random draw. The argument was based on the fact that, in many mammal species where investments in offspring are high, females are a safer evolutionary bet than males.

That is, with few exceptions, a female who wants to have offspring can pretty much accomplish that—they just need to rope a male in for a few moments. In a competitive environment, females want to choose the “best” sperm to produce their offspring (in balance with the desire to have a father around who will contribute to the care of said offspring).

So when resources are scarce, or when a female’s health is not in tip-top shape, or when she is at the bottom of the hierarchy, she skews toward the safer investment: daughters. This has been shown in red deer, cows, and even our cousins, the Barbary macaques.¹ I say, she skews, because the general theory is that such sex selection is accomplished by signaling within the mother’s body that leads to the spontaneous abortion of male blastocysts (early embryos). A lower level of blood glucose tells the womb that things are not pretty out there…

We found that—contrary to prior studies, which failed to exclude non-biological children—sons, not daughters, made parents (of both sexes) more liberal and more likely to vote Democratic. Curiously, while daughters made parents more Republican, they also made them more pro-choice. When we dug deeper, we found that the only issues on which the gender of offspring affected parental opinion were related to sexuality. Other partisan debates—guns, foreign policy, taxes, immigration, welfare, and so on—were unaffected. And while daughters caused parents to adopt more conservative views toward sexuality, they paradoxically made them more pro-choice. Or perhaps it isn’t so paradoxical but really just rational: Given that the costs of teenage, premarital childbearing are disproportionately born by the mother, parents of girls might prefer a more chaste sexual landscape and yet also prefer abortion to be legal just in case.

Of course, it’s hard to know whether our sons and daughters are actually changing us through social interaction. Does a baby girl’s actions make Mom and Dad see the world in a new light? Or does she merely tip the scales in terms of incentives? For example, Abigail Weitzman, a Ph.D. candidate at New York University, finds that across the less developed world bearing a daughter carries what she calls a “tax” that is borne by the mother. Mothers of first-born daughters are not only more likely to be abandoned or abused, they have to go to work at higher rates. Evidently, fathers want the mothers of their sons to stay home and raise them. But they aren’t willing to forsake additional family income in the case of nurturing daughters.

Read the rest here.