Again, I'm not making a contention, just suggesting a possibility.
Furthermore, I admit that some factors are social--for instance, if software development weren't a low-status profession in the US, there would probably be more women developers. I'm just not convinced that it all comes down to social factors.
If so (all pop evolutionary psychology and sociopolitical agendas aside) that's a depressing thought, because that would mean there is absolutely nothing that can be done about it.
It's not a depressing thought unless you have a sociopolitical agenda of having every single profession evenly split between men and women.
I like to think that I don't. I am however uncomfortable with the makeup of this specific field because I believe it is missing out on a huge potential source of creative and intellectual influence. In other sciences, this is not even a problem: there is no shortage of women hacking DNA, for example. So this makes me vaguely optimistic that CS could in theory be enriched by better recruitment.
Decades ago, there were no women surgeons because it was perceived as not being "in their nature". Look at hospital staff today, the situation is changing profoundly. I hope some day we can do the same for software development.
Further, you are misunderstanding the idea I'm proposing. I'm sure there are individual men who have, for instance, very poor spacial reasoning and individual women who have very good spacial reasoning. One does not reason about individuals the same way they reason about populations. As a population, men, on average, might be better at spacial reasoning. As an individual man or woman, a test of spacial reasoning will yield orders of magnitude more data about their spacial reasoning abilities than simply observing their sex. I have many personality traits that are more common in the opposite sex--I'm sure most people do. It's a fundamental misunderstanding of averages that leads one to take this as evidence for your viewpoint, however.
Ultimately, measures of a population only explain populations. They may explain why, as a population, most programmers are men. They do not explain why your sister is or isn't a programmer.