Not necessarily about the growth drive (Patreon)
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For example, the weight gain nation could go from overeating and simple softness to more extreme weights becoming commonplace, with meals more numerous and larger as time goes on, until the population is all immobile or near-immobile, spending most of the day stuffing their faces.
Then the pregnancy nation could go from supporting large families and the idea that nearly all women go through multiple pregnancies to, say, consolidating pregnancy in the hands (wombs) of an elite. Sort of like what I've been doing with the Zaharoff series, where a chosen few experience increasingly larger pregnancies.
And there could be other factors that get developed as time goes on. In the pregnancy nation women are lauded for being mothers, respected and cared for by the population as a whole, while in the muscle growth nation only women achieve massive growth, creating a matriarchal culture where men are seen as the lesser gender.
This is me mostly spitballing right now. I started to come up with the idea in the middle of the night and I'm still toying with it. I still need to figure out what sort of conflict the different nations would come into. Maybe there are three goddesses using the humans as proxies for an argument of theirs, and they debate which civilization is achieving more as the ages pass.
Virtually no chance I could use this for the growth drive, though, because how would I figure out how to distribute the money? Unless I asked for direct donations, which I'm hesitant to do because I expect the response would be muted.