Millennials are replacing historically rigid divides with more egalitarian relationships. In the process, men's actions and sensibilities appear to be converging with women's in remarkable ways (and vice versa).

Here are 5 key ways that many men are changing today:

1. Childcare and Housework

Decades ago, the emergence of appliances such as washing machines, refrigerators, and vacuum cleaners liberated families (but primarily women) from the drudgery of much domestic work (1). As more women entered paid full-time employment outside the home, men compensated by assisting more with the child care and housework (although the amount of time spent on such chores is still not equal). In more and more cases, fathers have assumed the role of primary for their children, a shift which has generated a changed sensibility between men and women.

2. Expression of Tender Emotions

Modern men, being more integrated into the daily lives of their children, are more likely to report looking forward to spending “quality time” with them. They discuss their children at work more often and are more likely to change their work schedule to accommodate their children's school pickups, sports events, and other extracurriculars. Such preoccupations typically involve greater expression of the tender emotions of love, affection, pain, sorrow, and sadness. Fathers are becoming more directly involved in negotiating disputes among siblings as they occur, instead of being disciplinarians of last resort (i.e., "Wait until your father gets home!"). Additionally, men today are more likely to cry in public than in the past, expressing a degree of vulnerability formerly considered to be effeminate.

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3. Care Over Appearance and Clothing

Physical appearance has traditionally been perceived as more important for women's social and reproductive success than men's, explaining why in most societies women primp and preen more than men (there are exceptions, such as the Wodaabe herders of Africa's Sahel, whose men go nowhere without a mirror to adjust their makeup and hair). Women still devote more time and money to their personal appearance than men do. But men are catching up: At age 20, female spending on clothes averages $400 annually. According to a study by Goldman Sachs, this spending rises steadily into women's early forties, peaking at more than $700 before declining during old age. Another report from the Consumer Expenditure Survey finds that single men spend around $400 on clothes annually, whereas married men average just $280. This suggests that men may also dress to impress potential mates; married men, who no longer need to attract a mate, get by with a utilitarian minimum in their sartorial budget.

4. Reduced Physical

Historically, fighting in wars was primarily a masculine activity, in part reflecting greater masculine size and muscularity. Moreover, the reproductive success of a community in conflict depended more on the number of female, rather than male, survivors; males were more expendable. Men are also historically more likely to fight over women than vice versa. However, research on homicides and other violent crimes shows that men have become progressively less violent over the past six centuries (2). Since men are responsible for about nine-tenths of violent around the globe, this means that modern men have become less different than women in terms of violent criminal behavior. This pronounced change reflects a modern world in which men no longer win mates through the violent intimidation of rivals, with some exceptions, such as violent criminal gangs (3).

5. Reduced Interest in Casual Sex

Violent or not, men have historically been expected to be much more interested in casual sex than women; women have long been perceived as having a greater biological investment in children. Since males give less than they get, the argument goes, they are more eager to mate more often. As countries become more affluent, however, women become more interested in casual sex and men less so; the gender difference declines to vanishing point (4). The majority of women are now sexually active before , and one reason, then, that men may have grown less interested in sex is because it has become a less scarce resource (1). Further, has been largely decoupled from reproduction via widespread availability of contraception. Finally, women have grown more aggressive in their own pursuit of mates; men report avoiding sex with "needy" needy women as assiduously as women once avoided "pushy" men.

1 Caplow, T., Hicks, L., & Wattenberg, B. J. (2001). The first measured century: An illustrated guide to trends in America, 1900-2000. La Vergne: TX: AEI Press.

2 Pinker, S. (2011). The better angels of our nature: Why violence has declined. New York: viking Penguin.

3 Palmer, C. T., and Tilley. C. F. (1995). Sexual access to females as a for joining gangs: An evolutionary approach. Journal of Sex Research, 32, 213-217.

4 Barber, N. (2008). Cross-national variation in the motivation for uncommitted sex: The impact of disease and social risks. , 6, 217-228.