I've had this idea for a while now, here's the basic premise:
Several centuries into Earth's future, with the advent of genetic engineering, more and more people chose to become hermaphrodites or 'futanari'. This ended up being passed on to their children, with non-futanari becoming an increasingly small minority. Eventually, it reached the point where everyone was a futa.
This change brought significant changes-not the least of which was an increase in everyone's libido. With both male and female hormones racing through everyone, older attitudes towards sex were discarded. Soon, it became acceptable to masturbate openly at your desk at work, and before long, laws regarding nudity and sex in public were repealed. Technology quickly developed a way to use all the cum people were producing in other ways, mostly by turning it into other stuff. Additionally, genetic manipulation grew even more, to the point where it wasn't strange to see people walking around with demon horns or elf ears or even as an anthropomorphic creature.
People still date and romance each other, marriages are still held in high honor, but the act of sex is given far less importance-kissing in this world is practically 'hello', and sex is considered as important as a handshake. It's just something to do, and it just happens to be really fun. Incest is not so much frowned upon, but it is regarded as a sign of being a shut-in; after all, wouldn't you be concerned if someone never went out among other people? Not even to go buy a book or something?
As you might have guessed, this idea is incredibly silly and not at all serious. If you're interested, shoot me a PM! If not, then have a wonderful day!