I’d like to propose a thought experiment. Suppose the sciences of biology and medicine advanced to the stage where it became possible to change the sex of an animal (including, of course, human animals) completely. Let me make a few more stipulations. The change would be complete at every level. A woman transitioning to become a man would grow a penis and testicles; a man transitioning to become a woman would grow a vagina, clitoris, ovaries and breasts. These organs would be fully functional. The Now-Man, as I shall term him, would be able to produce sperm, ejaculate, and father children. The Now-Woman (if of appropriate age) would menstruate and be able to become pregnant, bear children and lactate. (I don’t mean that either the Now-Man or the Now-Woman would be defined by actually producing children, but by the capacity in principle to do so.)

Secondary sexual characteristics would also be altered according to the target sex: facial and body hair, musculature, height, bone density, lung capacity, physical proportions and so on. This means that some of the changes would be retrospective; that is, changes occurring during and after puberty would be reversed. So a man of average height transitioning to be a Now-Woman would lose some absolute height and become of average height for a woman; a woman of above average height would become an even taller Now-Man, and so on.
The transformation would go all the way down to cellular level. A scientist examining a single cell of a person who had undergone this process would identify that cell as female, if the person had transitioned to be a Now-Woman, or male, if the person had transitioned to be a Now-Man. What we are talking about, then, is a complete metamorphosis. Since it will be convenient to give the process a name, let’s call it Sex Metamorphosis.
Here are some further stipulations. First, the process would have no negative side-effects. It would be safe, painless and would not affect long-term health. Second, the process would be inexpensive, available to anybody who wanted it. Third, the process would not be unduly protracted. It would take no more than (say) a few weeks. Finally, the transformation would be fully reversible. If you weren’t happy being a Now-Woman or Now-Man – or were happy enough but decided a year or two was all you wanted – then you could metamorphose back to your original sex.
This is an utterly implausible science-fiction scenario. But it’s a thought experiment, remember. Bear with me. If it were possible, what consequences would follow?
I would expect the opportunity to meet with considerable uptake. And I mean in the wider population, not just those who are trans. I myself, though not trans in the smallest degree, would be keen to try it. At my age I …
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