The Big [Censored] Theory

Is aversion to discussion of sex a part of traditional Chinese culture? Seems odd given I'm not aware of any puritanical religions taking hold there.

Why would a culture require a puritanical religions to have an aversion to discussion of sex? And do you consider an aversion to discussion of sex to be default lacking or present in a population?

Because why else would such an aversion arise? I don't think there are any sensible "defaults" for human cultures. But I wouldn't expect aversion to talking any sex to arise spontaneously among a population that hadn't had it imposed by prior generations or from outside. We're naturally curious beings and have lots of sex (compared to other species).

Is there any culture in the world without significant taboos or social rules around sex?

I can totally see why that’d be the default, simply because sex is such a charged act in any culture. Purely biologically: it’s a very vulnerable act and has tons of “political/social implications” in a social species. Who you have sex with and be that vulnerable with signals your “allegiance” in a sense.

Even chimps have taboos and social rules around sex for this reason. Who you have sex (or don’t have sex) with decides who’s in charge, who you support, what your clique is, and so on. A chimp caught having sex with the wrong chimp might be attacked.

Chimps, as far as I'm aware, don't talk about sex. I suppose my naive view is that the more society is prepared to talk about their behaviours, the less likely it is we'll indulge in the worse aspects of such behaviour. Hence taboos over discussing particular subjects have become ingrained despite being most likely counterproductive, at least for society at large, even if they serve the interests of some.

I was primarily responding to your suggestion that strict social rules around sex were an intrinsically Christian take (or religious in nature).

Beyond that though, Chimps have social hierarchies around sex. It’s hard to imagine why something you believe to be so counterproductive would exist so persistently across cultures and times unless it had serious value.