I don't like to mention it but

Your potential Nobel prize now casts a long shadow over the conversation

What is the other biological function you have identified?

As a biological function sex exists for the purposes of procreation of course. We are all familiar with the basic mechanics of penis in vagina and need be no more graphic than that. In order to encourage all living species to procreate in this way, it has evolved as something we increasingly desire the longer we go without it and as something inherently pleasurable when we do it. Though this tends to diminish in later years and eventually in old age many of us will lose interest altogether.

So biologically the purpose of sex is penis in vagina to make babies. It has evolved to be pleasurable so that we want to do it fairly often especially in our most fertile years.

But in the case of humanity, we have also evolved intelligence and powerful imaginations so that we have come up with more ways to enjoy sexual pleasure beyond the mere procreative act, ranging from masturbation, oral sex and anal sex to fetishes of various kinds. Not to mention some people seeking pleasure in threesomes, foursomes, or even moresomes. And even the procreative act itself is often done purely for pleasure, with contraceptives employed to make sure procreation doesnt take place. This makes the intercourse entirely pointless from a biological perspective, indulged in purely for pleasure.

In effect, our imaginations have perverted many of us into interests that go beyond mere procreative intercourse. This can become a real problem in some cases when the interests someone develops becomes something like paedophilia, for example. But the innate problem is that human imagination has turned sex entirely into a source of pleasure with procreation mostly held in check until people want kids.

Humans might well be unique in the way we interact sexually. No other animal exhibits the range of practices and perversions known to man. For other species, little if any imagination seems to be in evidence and it is mostly limited to the procreative act. And it seems likely that none of them are even aware of the connection between intercourse, and the subsequent birthing of new borns. It is just something they do by instinct and because they experience pleasure when they do it. Some of them can also experience powerful sex drives, as anyone who has ever owned a dog in heat will have seen. But it seems to be entirely biological.

It is our imagination and its application to sexual pleasure that sets us apart but also creates many social and societal problems. Ie when people develop sexual interests that are harmful to others, the most extreme example of which are probably sexually predatory serial killers. And it must always be a bit of a freak out if your partner suddenly asks if you want to do such and such a perverted act with them, lol

Sorry, where did I say sex was just a biological function

We all knew what a homo was and a mummies boy was raised in a way that made him effeminate. Perhaps today, there are so many single mother children.

I feel like i have said this before..but -

Earlier in the thread someone suggested that the binary notion of sex was an arbitrary cultural construct and I have simply pointed out that it isn't arbitrary at all - it is based in reality.

you do realise chimpanzees are quite inventive ?

I’ll say no more than that.

That is a far more interesting question / issue.