What cause a society to have, in general, boys who lavish time and money (ie resources) on to girls and get much less in return?
I can think of cause that falls under two categories, namely economical and biological.
Oversupply male or shortage of female will lead to stronger competition among the boys (compare to competition on the girls side). This is obviously. But what may contribute to the oversupply of males? I offer these scenarios:
A: There are more mate seeking males than females, leading to oversupply of males. (Many reasons can cause this: higher female mortality rate, more boys willing to move to big cities than girls leading to oversupply of boys in big cities, etc).
B: More selective boys (eg. they all only want certain types of girls). This will reduce the number of “desired” female thus effectively causing female shortage.
C: Boys cheats more. For every boy who cheats there is an extra supply of boy, effectively causing oversupply.
Biological cause are well known (i think). i cannot do justices here in a short blog post, but it goes something like this:
Females contributes far more than males in the act of procreation. Female eggs cost more than male sperm, females nutrition are directly siphon off her by the offspring during and after pregnancy (milk). Because of the overwhelming cost to her in the act of procreation, and her reliance on her partner to feed and care for her during and after pregnancy she needs to avoid bad partners who runs off after conception.
So it become a good evolutionary strategy for her to demand “down payment” in the forms of food and other resources before conception. It is more than probable that this courtship behavior from our evolutionary past still linger in modern societies today.
Update: the risk of unwanted pregnancy and violent (rape) may also cause girls to be less incline to have sex or go on a date with a physically stronger, unfamiliar man, respectively. It is therefore foreseeable for girls to be pay less for dates in order to compensate for the risk.
Note: i though about taking differentiation of income between the sexes into consideration, where if boys general make more money than girls, it is likely that boys will spend more on a date with a girl. I decided to leave it out because, i want to concentrate on male-female asymmetric contribution to the relationship. It is arguably not asymmetrical when the boys spends more in proportion to their extra income.
I also contemplated on adding a “cultural” reason to the asymmetric contribution (eg being a “gentlemen”). However, its difficult to tell if the cultural reasons are not simply manifestation of the underlining economical or biological reasons already stated above. I therefore left them out. Even though there are probably evolutionary foundation to the economical cause i stated above as well.