Women tend not to have penises.

I am sure you were joking, but to clarify and expand: Why do men seek contact with the opposite sex more frequently than women? Why do they tend to do so in a way that seems to bother the woman in question? Why are women not doing the same to men?

...seriously? well, because women and men experience life very differently. being a woman is a lot more dangerous - you are simply too weak to defend yourself against most guys. so, you have to trust that they will treat you fairly before sleeping with them or starting a relationship, and if you're wrong, the consequences are terrible. men simply don't have to worry about consequences this severe - as a guy picking up girls, you never have to wonder if they will rape or abuse you.

remember that rape is still exceedingly common (1 in 3 women in the USA will be sexually abused at some point). women are just as sexual as guys, it's just much more dangerous (and socially unacceptable - slut-shaming, etc) for them to solicit sex. as for why anonymous dudes on the internet are so creepy, it's most likely a combination of the disinhibition anonymity gives you and the sexual deviance a boner gives you.

Because they don't need to, in general; and because reproductive biology predisposes women to be choosy (as the physical burden of pregnancy and childbirth on women is enormously high).

Part of it is purely game theoretic.

Once one person realizes it's a successful strategy to send more messages then their competition, their competition also has to send more messages. Arms race quickly ensues. And once you have such an arms race on one side, the other gender no longer has to even bother initiating conversations.

Why did the arms race tip towards men competing and women getting it easy? Probably cultural norms. But once the arms race got started, there was no putting it back in the bag.

> "Why did the arms race tip towards men competing and women getting it easy? Probably cultural norms."

Cultural norms that are followed by every live-birthing animal species, how strange.

Incorrect. For example, the bonobo.

Because it costs far more for women than men to have children, biologically speaking.

That's an intellectually lazy excuse: humans are social creatures – completely ignoring that (and the existence of birth-control) to rely on biological determinism ignores most of the things which make us human.

(Put another way: your explanation would cover our closest relatives: chimps, gorillas, orangutans and bonobos – given the huge differences in behavior, a simple reproductive cost model is obviously incomplete)

I think the three other responses you had received to this comment when I post this give a more general answer: No one knows, and most fall back on evolutionary psychology to come up with a plausible-sounding explanation.