So what happens when bodies are easy to change? In QC, AI have the option of changing chassis. But at some point in the not-too-distant future (probably in time for our greatgrandkids anyway) body modification for humans will become indistinguishable from being born that way.
Imagine that a man can decide in January that he wants to try being a woman, start taking some pills, and by the end of February, be a woman - physically, hormonally, and in every other way, six inches shorter, fifty pounds lighter, with whatever bustline/etc she decided on. So she stops taking the pills, acquires a nice wardrobe, and makes her way from there.
Um. It didn't quite happen that way for me, but close enough.
I don't like discussing personal and private details, and only do it if there's some educational objective to be attained.
I have the 3beta Hydroxysteroid Dehydrogenase Deficient form of Congenital Adrenal Hyperplasia. Which means my whole steroidogenesis is SNAFU, including but not limited to the sex hormones. While those have the most spectacular visible effects, my health is more contingent on cholesterol, cortisol, minerocortisoids etc. Changing sex naturally is irrelevant if the patient dies from related causes, even if it is unusual, spectacular, even shocking to observers.
No pills required, height only changed an inch due to cartilage thickness changes, 80 rather than 50lbs lighter, and it took 3-6 months not one. Some structures atrophied, nothing new but apparently some structures were present though vestigial. 3BHSD can cause that in the womb, and usually any change happens before birth not after. We think. It's rare, and no two patients are quite the same.
As I said, close enough to your
gedankenexperiment.
First, sex hormones affect the adult brain(1). There is some degree of neuroplasticity in some areas (though not others). With such a rapid physical change, the alterations in thinking that nearly everyone gets in puberty are obvious, rather scary, and disorientating. You can feel your brain rewiring. It takes some degree of philosophical and medical knowledge to retain a coherent sense of identity, the knowledge that your personality is performance art not sculpture, you are not quite the same person today as you were yesterday, or will be tomorrow.
This is just the same thing on steroids (so to speak).
Maybe a few years later, when she has a husband and a couple of kids, she and her husband decide to swap, so they both start taking pills, and a couple of months later they change their designations from "husband" to "wife" and "wife" to "husband" and the kids take a few weeks to get used to it and the oldest decides maybe he ought to be a daughter instead of a son and does that, and life goes on.
It doesn't work that way. Or at least, not usually. Observations of those who have had involuntary natural sex changes due to 5ARD, 17BHSD, 3 BHSD(2), and very intersex kids who have been surgically assigned a sex suggest that about 1/3 are male, 1/3 female, and 1/3 can function adequately as either gender. With lesser intersex kids, it's probably closer to 45%/45%/10% but we're not sure.(3)
What that means is that in your thought experiment, there's around a 3 in 4 chance of disabling Gender Dysphoria developing. Though it might be less in someone who wants to try a swap.
References:
1)
http://www.eje-online.org/cgi/content/full/155/suppl_1/S107Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure by Pol et al, Europ Jnl Endocrinology, Vol 155, suppl_1, S107-S114 2006
Results: Compared with controls, anti-androgen + estrogen treatment decreased brain volumes of male-to-female subjects towards female proportions, while androgen treatment in female-to-male subjects increased total brain and hypothalamus volumes towards male proportions.
2)
http://www.ncbi.nlm.nih.gov/pubmed/16010463Gender change in 46,XY persons with 5alpha-reductase-2 deficiency and 17beta-hydroxysteroid dehydrogenase-3 deficiency. Cohen-Kettenis PT. Arch Sex Behav. 2005 Aug;34(4):399-410.
However, an estimation of the prevalence of gender role changes, based on the current literature, shows that gender role changes occur frequently, but not invariably. Gender role changes were reported in 56-63% of cases with 5alpha-RD-2 and 39-64% of cases with 17beta-HSD-3 who were raised as girls. The changes were usually made in adolescence and early adulthood. In these two syndromes, the degree of external genital masculinization at birth does not seem to be related to gender role changes in a systematic way.
3)
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1421517Discordant Sexual Identity in Some Genetic Males with Cloacal Exstrophy Assigned to Female Sex at Birth by Reiner and Gearhart, N Engl J Med. 2004 January 22; 350(4): 333–341.
RESULTS Eight of the 14 subjects assigned to female sex declared themselves male during the course of this study, whereas the 2 raised as males remained male. Subjects could be grouped according to their stated sexual identity. Five subjects were living as females; three were living with unclear sexual identity, although two of the three had declared themselves male; and eight were living as males, six of whom had reassigned themselves to male sex. All 16 subjects had moderate-to-marked interests and attitudes that were considered typical of males. Follow-up ranged from 34 to 98 months