Wait – I thought back then (1950s/60s/maybe 70s), "programming" refered to something more akin to data input, i.e., someone designed a program, and the "programmer" entered that program into the computer's memory, using punch cards or whatever [1]. Later, this activity and the designing of a program was merged and done by a single person, as it is known today.
If this is true, then the mystery is not why women's preferences changed since the 1970s, but why their preferences seem to be different from men's, back then and today.
[1] You can still find this terminology in the hardware world. For example, storing the bitstream into an FPGA's SRAM or flash cells is called "programming the FPGA", and the little box which is sometimes necessary to do this, is called a "programmer" – which is kind of funny if you think about it.
That's exactly right, "programming" was considered secretarial work, and guess what, pretty much all secretaries were women.
Male engagement in programming exploded with the advent of personal computers in the 80s, and female engagement chugged along at the same growth rate as before.
https://nces.ed.gov/programs/digest/d12/tables/dt12_349.asp
The "programming as secretarial work" happened in the 50s and 60s which predates this data, so I haven't found a canonical source for that.
It can also be the case that the whole thing is a dynamical system (for example driven by desire to work in a field which already has majority in the same gender), and it somewhat chaotically "oscillates" around the equilibrium. So there really is not an causal explanation as such.
The "woman in programming" example is much better. Woman in programming started declining basically the moment computer games entered the market, since computer games are marketed primarily to males (outside of mobile, but that influence is fairly new). If we just simplify the whole problem to this one influence, woman are not programmers because of the marketing of "children toys". Is that bad, something we have to change? Nobody is really prevented from choosing to do certain freetime activities, to get exerience and motivation. They are just notpushed towards it. Still it leads to an unequal outcome.
Secondly, nowadays, men and women both play games at roughly the same rate (with women playing a little more by some metrics), but that doesn't seem to have improved the chances of women entering the programming industry. What is the explanation for that (besides that it's "new", which isn't really the case anymore)? Like many people, I got into programming as a result of video games--but I find it hard to believe that that alone is responsible for the entirety of the observed difference in behavior.
Finally, what is your explanation for the huge increase in the proportion of women in biology?
It is true that the gender imbalance in gaming has mostly smoothed out, but until that happened the software industry already turned mostly male. And even if nobody intends to erect barriers, in a group that's heavily skewed towards one demographic everything starts to cater towards that demographic, pushing everyone else away. So unsettling the balance once for long enough may be enough to explain where we are today.
>Finally, what is your explanation for the huge increase in the proportion of women in biology?
I honestly have no idea.
I don't know why less girls choose computer science than do boys, but I don't think it can be so heavily linked to gaming. The gaming community is actually sometimes far harsher on girls than the comp sci community, yet girls continue to choose gaming. In the gaming community, a girl is either a "thot" or she beats out every male who plays against her. If you're neither of these things the community still believes you're one of them and will react to you/attack you accordingly, usually defaulting to calling you a "thot".
In comp sci, the barrier is more about socializing. It may be a stereotype but I have noticed that many males in comp sci are the less socially-gifted ones. It is often not possible for a female to join such a group of males because they are scared of her. Other than that, the comp sci world in academia is far less disgusting than the gaming world and far less hostile. It's about avoidance instead of outright attack.
It could just be that girls enjoy programming less than boys do. I'm not saying that's definitely the case, I'm saying it seems more likely than not.
Or, to bring up a very timely example: currently there are no legal barriers to coming out as transgender (in the U.S., anyway). I still think it's reasonable to say that people are not "free to choose" to transition, because in many cases they will be ostracized or (legally) discriminated against for it. This is similar to the status of homosexuality (though it is a less direct analogy since there were many more laws explicitly prohibiting homosexuality).