With MACR, disease, age and most injury could be cured entirely. Repeated treatments had the potential to end death itself, making humans immortal.
But this all came at a price for half the population. MACR worked by resetting the body entirely, erasing all it’s ailments, but also erasing the influence of male hormones in utero. Any man treated with MACR would become a woman.
On one hand, this helped solve the potential over-population issues that might come from universal immortality. On the other, it also created a technology trap. How would humanity recover if MACR was lost and there were no more men?
To mitigate this risk, Born males are not permitted to use MACR until their 40th birthday. At 40, most men are attached to their gender identity, so they continue to delay.
Arnold had loved being a man, At 83 he had been one of the few men his age left in the world and younger women would seek him out as a novelty. He was in bed with three of them when his heart started to give out. They administered MACR to save him.
Now, reset to age 20, Arnold has to pick a new name for this new body. Immortality feels so wrong, she hopes she gets used to it.