Jackdaw - and in fact reading a lot of this thread, perhaps we need to adopt Indian, Samoan and many of the Pacific Island practices who have a third sex embedded in their society.
In India/{akistand/Nepal, the 3rd sex is known as Hijra, Samoa it's the Fa'afafines, Madagascar the Sekrata and Indonesia, the Warias.
Then there are third sexes in Mexico - the Muxes, The Oman - Xaniths, Indonesia has also five sexes defined in the Bugis tribe.
In old North American Indian sociert 'two-spirited people' were recognised and in Judaism there are six sexes. There's also a third gender in the Dominican Republic.
I'm not going into a long and detailed account of their practices and beliefs and the tensions therein - for the Hijras, it's almost been a lower caste status thanks to the Brits not recognising them, even declaring them illegal. The point is that these societies tolerate the third sex and may be there are some learning lessons to be had about assimilation and being more appreciative of the psychology that defines our sexual wants and behavioural responses in society.
I'd also like to take 'issue' with an early 1st page point that Naomi made when she laid into men becoming female - it is 'hey, it works the other way around, there's quite a rise in FtMs out there - I know of one in the States who has gone to extraordinary lengths to change her life to his.....in fact, termed tumtum in Judaism and calalai in the Bugis tribe.