Lest anyone get the wrong impression, I'd like to make three things clear. First, I'm not deeply attached to this, it's just an idea I've been kicking around; please, discuss. Feel free to prove me wrong. Second, I'm generally--and still--an advocate of a very man-friendly reading of feminism, which is not clear from the content of this post. Lastly, I like men. A lot. Even if this theory happens to be right. Ok, now we can start.
I have a theory that since men held so much material power in sexual relationships for such a long time--the ownership of all property, children, and spouse, and a greater right of divorce, among other things--women have, for a long time, been more or less forced to do the work of emotional and interpersonal regulation for both parties.
There's a pattern often found in abusive relationships. Anybody who grew up with a severely physically abusive parent will recognize it; constant threat of violence changes the way you see the world. Your behavior and emotions are absolutely dominated by the goal of keeping yourself (and perhaps also the people you love) safe--which you do by trying to keep your abuser happy, at basically any cost. There is not possibility for give and take in this sort of relationship, no honest communication or mutual recognition of needs. The child is basically not allowed to have needs, particularly not emotional ones.
This is exactly the sort of power over others that has traditionally been afforded to men within marriage, generally without negative physical, legal, or social consequences. Despite the fact that, even in the most brutal times, there were probably lots of men who were decent enough not to engage in this sort of terrorism, I think the fact of it's possibility probably had a large impact on women's functioning over time.
And so we arrive at the (usually essentialist) argument that women just care a lot more about relationships and emotions than men seem to. I think this is definitely the current state of affairs, and that if we're interested in any form of gender equality it can't and shouldn't be ignored.
Here's some evidence:
When addressing ethical challenges women are more likely to place a high value on taking care of people's emotions and creating collaborative solutions to problems--instead of focusing primarily on principles, as men are more likely to. Regardless of technically having access to all fields, women still choose their work by very predictable criteria--on average, we're far more likely than men to be motivated into our career path by wanting to help people. We also want a lot more emotional feedback from our professors then men do.
Perhaps most tellingly, we perform far better--especially in technical fields--when placed in classrooms with no men, whereas men perform the same or worse in single gender classrooms.* Usually people explain this in terms of men showing off for women, and women "showing off" their suitability as mates by not being intellectually intimidating.
I think it useful to contextualize this differently. What is a woman doing when she chooses not to be intellectually intimidating, other than looking after the emotional welfare of her potential colleagues and partners? And why is it that, rather than recognizing that by looking after people's emotions she is performing a valuable service (maybe the reason some studies show that men perform better with women in the room?) which needs to be done by somebody in order for everybody to function well, we simply try to "empower" her out of it?
This is a problem I see with basically every kind of "women's work." Liberating some women from housework doesn't change the fact that housework definitely needs to be done--and that this problem is often "solved" by hiring someone of a lower economic status to do this thankless job instead. Encouraging women not to be completely bound to parenting doesn't change the fact that parenting is a spectacularly important project, which deserves to be done well. The wage gap (for the same hours working outside the home) between mothers and non-mothers is far larger these days than the wage gap between men and women; chew on that.
When you look at the lives of great intellectual men, they are often littered by complicated, even ugly relationships with bright or even brilliant women who never accomplished anything particularly visible themselves. Maybe, there was work going on there too--work of a different kind, work that we ought to recognize. Maybe it will never be possible for women to reach their full technical and intellectual potential until men start to reach their full emotional and relational potential--until men start carrying their weight in doing the work of relationships, along with all the other marginalized kinds of work traditionally left to women.
*Not better or worse as compared to one's classmates, but on national standardized tests like the GRE subject tests.