So as to fill my blog, I salvaged this old unpublished draft from my dustbin; I'm not sure I agree with all of it, but maybe it's food for thought for you, and you may come up with something better -- and maybe even something better that's well known for a long time by in evopsy circles.
Amongst humans, like in most species, (and particularly so in days of welfare state,) children can survive without high paternal involvement: indeed, female genes have already chosen the high parental investment strategy before birth, so that rearing of children after birth is but an extension of their strategy, whereas it goes opposite to the initial male strategy of small gamets. There are exceptions, of course, and paternal parental investment is rather high in humans as compared to other species; in any case, what matters is that there is high potential for lack of paternal involvement in children rearing, whereas there is little such potential for maternal involvement.
Thus, males are in sexual competition with all other males at every moment of the day, every day of the mating period, for the womb of the few available females. Females on the other hand, are in sexual competition with all other available females, but only once per mating period, for the best males they can find, and may compete potentially separately for a one mate that brings best genes and for a one sucker that may help them rear children. That's quite a difference.
This explains why sexual competition requires a lot of physical and psychological aggression among males, physical domination of males over other males as well as females, whereas females will compete for psychological manipulation of males. This explains why males are on the demand side of sex, yet have the initiative of the courtship, whereas females are on the offer side of sex, yet have a mostly passive but decisive role in courtship. The fact that offer rather than demand of sex is usually passive with respect to marketing (except for whores, whose offer is exceptionally high), means that sex to women is much like money to men: it is something to be kept or spent so as to acquire something good.
Now, females are also in some social competition for the committed attention of some male or some other, while they breed their spawns --- and usually, a male will only give his attention to a female he expects to reproduce with, or together with whom he breeds spawns (he believes) are his own. But this competition is much milder than the sexual competition, and usually takes place but as an aftermath to the previous one, among a limited set of known competitors; so it modifies the sexual behaviour of individuals but it doesn't define the main trends. This competition is also reduced all the more since nowadays women have some financial independence, and that state welfare reduces their incentives for competing on long-term relationships, and increases their relative incentive to invest in seeking better males to mate with.
Incidentally, this is why seemingly egalitarian laws such as state welfare actually increases inequalities with respect to the most important animal satisfaction, sex. Talk about anerisms! That said, considering how nomenklaturists of social-democracies and social-dictatorships take sexual benefit from their situation of power (oh the stories my uncle told me about his trips to communist Europe!), it is as much subconscious self-serving hypocrisy as it is delusion of one's own consciousness as an instrument to sincerely delude other people.
Of course, in the sexual market, there are also a few greatly attractive alpha males (e.g. zillionaires, socialist nomenklaturists, warlords), who may raise the interest of females and induce an intense competition among them. In such circumstances, some able females will compete in desirability, at such a point that they may become quite an unreachable fantasy for the common males. So some phenomena exist in reverse order among males and females; but is never a full symmetry in male/female relationships, only an escalation in the stakes of social and sexual competition. And indeed, these alpha males don't stop competing with beta males for all those attractive females that don't actively go after their money or power.
Hum, depressing news for beta males; so I better go and workout some alpha male status while I'm still coté à l'argus.