In an email, Amanda Clayton, a professor of political science at Vanderbilt, described the political transformation of women starting in the 1960s:

When women did not work, they would often assume the political preferences of their husbands. When women didn’t have access to income they held more socially conservative views in part because they wanted to protect the sanctity of their marriages and shore up against the possibility of divorce lest they be left without a breadwinner.

That changed when women began to have their own sources of income:

When women began to work, we see the beginning of the divergence of political preferences. Because women often work in jobs that are lower paying then men, they often have stronger preferences for government social services and typically tolerate higher levels of taxes that help pay for such services.

Emily Jacobs, a professor of psychological and brain sciences at the University of California — Santa Barbara, replied to my inquiry:

When “the pill” was released in the U.S. in 1960 it revolutionized women’s reproductive health. For the first time in human history, women could have sex and have complete control over their own reproductive function. By the late 60s and 70s women’s enrollment in four-year colleges and the work force surged and they gained economic independence.

The issue of women’s control over their own bodies, Jacobs argued,

has shaped the social and political landscape ever since. I think the rise of Trump reflects a deep-seated insecurity over men’s social role. They are no longer sole breadwinner and, as Piers Morgan would have you believe, child care is the ultimate demasculinizing act.

Heather L. Ondercin, a political scientist at Wichita State University, similarly identified the 1960s as the key turning point in relations between men and women:

The course of tension and conflict between the sexes after the 1960s is complex, but can be summarized as a conflict over traditional ideas about gender that preserve the privilege of white, heterosexual males and ideas that want to change gender roles and ideology.

It’s possible that the emerging disciplines of behavioral ecology, behavioral biology, population genetics, evolutionary biology and so on have something to contribute to our understanding of the political gender gap. (For an overview see Bobbi Low of the University of Michigan, “Why Sex Matters: A Darwinian Look at Human Behavior.”)

Steven Pinker, a professor of psychology at Harvard who argues that “the mind is a product of the brain, that the brain is organized in part by the genome, and that the genome was shaped by natural selection” contends that

there is a persistent political gender gap in the trade-off between guns and butter: men are likelier than women to favor the more hawkish and law-and-order candidate, women the candidate who promises more social spending. The asymmetry is hardly surprising to an evolutionary biologist.

This difference, Pinker wrote in an email, emerges from that fact that

males of many mammalian species compete for dominance (which in traditional societies translated into more mating opportunities, hence more offspring), including the dominance of their group relative to other group. They are often willing to take lethal risks to get a shot at the jackpot of being an alpha male or part of an alpha group, especially since their offspring can survive without them, albeit at greater risk.

“For females,” Pinker continued,

such a risk is insane: they won’t bear any more offspring if they are more dominant (since unlike males, their reproductive output is fixed by the time it takes to gestate and nurse a baby), and their offspring can’t survive without them.

In terms of politics, Pinker argues,

the asymmetry is there, and it could affect gut-level sympathies: men toward politicians that embrace violence (the police and army) to enhance the competitive formidability of their perceived group against other “tribes,” be they foreign countries or rival races or ethnicities within their own country; women toward politicians that promise benefits to the health and education of children.

David Buss, a professor of psychology at the University of Texas, and a pioneer in the field of evolutionary psychology, wrote me that the sexual dynamics between men and women have changed over time.

First, Buss argues, there is the

mismatch between ancestral and modern work environments. Humans evolved as hunter-gatherers who engaged in periodic intergroup warfare.” Buss notes, “Warfare was almost exclusively a male activity. There is not a single instance in all of human recorded history of women forming a war party to attack another group and capture mates or territory from another group.

While “highly sex-segregated work environments,” Buss writes, were the rule “over 99 percent of human evolutionary history,” in the modern work environment “women and men are not only expected to work together, but, dramatically, they are now competing for the same jobs.”

The tensions resulting from “the increasing integration of women working with men and competing with men and each other for key positions in the workplace” are exacerbated by what Buss calls “inappropriate mating adaptations.”

Buss wrote:

When men and women interact, mating adaptations get activated, because people tend to be attracted to those with similar interests, and workplaces put people with similar interests into close proximity, and mating psychology gets even more activated.

“Add to this volatile mix,” Buss continues,

the evidence that men who attain positions of status feel “entitled” to greater sexual access to women — in fact that access was one of the key driving forces that led men over evolutionary history to have such strong status-seeking and resource-acquisition motivations.

Back in 1996, Buss proposed a co-evolutionary theory to explain the origins of “patriarchy,” suggesting that women were not passive pawns, as previous theories had suggested, but

that women’s preference for men with resources and men’s competitive strategies have coevolved — the outcome being a tendency for men worldwide to control more resources, power and position than women. There is strong evidence from a study of 37 cultures involving 10,047 participants that women have a greater desire for long-term mates who not only possess economic resources, but also possess characteristics that are likely to lead to resources over time, such as ambition, industriousness, and social status. These preferences, operating repeatedly over human evolutionary history, have led women to favor as mates men who possess status and resources and to exclude from mating men lacking status and resources.

Kay Schlozman, a professor of political science at Boston College, brings this back to the present, agreeing that “there is no question that gender conflict in politics has been exacerbated in the recent past.”

One source of conflict, she says, is

the threat to powerful men — who are not accustomed to being challenged and who sometimes feel wrongly accused — from the outpouring of revelations about sexual harassment and sexual assault.” Another source of contention, she argues, “is the feelings of resentment by working- and middle-class men who have lost relative social status in the wake of a variety of social and economic changes, including the growth in workplace opportunities for women.

Schlozman cautioned against exaggeration of

the extent to which enhanced gender conflict implies a partisan war between women and men. At a time when American politics is characterized by deepening divisions along many fault lines, there are men and women on both sides of the chasm.

Sarah B. Hrdy, professor emerita of anthropology at the University of California-Davis and the author of “Mother Nature,” contends that “underlying tensions and anxieties over gender roles are exceedingly old, and have surfaced again and again at different times, across many cultures.”

Gender roles, according to Hrdy,

have long been packed with tension. Nothing new. Carried to an extreme these tensions can result in oppressive restrictions, not just on women’s autonomy and opportunities but really damaging subsistence-threatening losses in freedom of movement and reproductive choices.

Hrdy wrote that there is “no doubt” that evolution is a factor, “having to do with primate male predispositions to control female reproduction,” but noted that she was hesitant to go into them

because the sources of these predispositions are really complicated — long-running evolution of female reproductive strategies and male counter-strategies, generating female counter-strategies.

Hrdy voiced her worries about contemporary developments in a 2018 letter she wrote her classmates in preparation for the 50th anniversary of her graduation from Radcliffe College:

Hrdy said she had been asked “What questions or issues do you think are going to be most important for women in the future?”