Zompist Bboard Again

I wrote:I'm trying to figure out how the gender roles in one of societies change and I'm stuck
"But they don't even have "man" and "woman" as genders!
They have a different gender system, although still have biological males and females
Gender is chosen in a solemn ceremony once you reach adulthood. There are two of them, and a marriage is between the two
The conculture eventually abandoned it to the same kind of gender system there was in early modern Europe (no sworn virgins though) after the collapse and conquest of their great cities"

as in the new system was from whoever conquered them?

I wrote:Yes, but it is not forced but I can't figure out the how
The details of the end culture are pretty open to mucking around with, so the how greatly affects that

"forced" is a pretty nebulous term. In real examples of colonialism, cultural things are sometimes not forced at gunpoint, but the colonial society rewards people for participating in the colonisers' culture

Could you have some sort of puritanical religious order?

(but the gunpoint method is there too very often obviously)
you could have for instance, if the institutions of the conquerors just don't acknowledge the conquered culture's gender system, and to be a part of them you have to conform to the conquerors' system instead

I wrote:There is some settlement, but it isn't a settler colony. The religion gets all 'interpretatio romana'ed. I agree that the institutions wouldn't recognise the system but that isn't enough of an obstacles
They could just assume outside roles for the sake of interacting with outsiders

I think it would still affect them outside that interaction with the conquerors, but you're right, it isn't a lot
Who owns the media? If it's the conquerors, there's opportunity there for indoctrinating the foreign system

I wrote:Media? Most people are illiterate in both cultures

assuming the society is modern enough to have some kind of mass media

I wrote:no, it is iron age

rip

Could you have prominent leaders who wish to get in the good graces refuse the cerimony?

I wrote:You mean refuse to let their children do the ceremony?

I feel like an iron age society with no settlement of conquered territories and no "forceful" spread of its culture simply would not have the means or will to change the gender system of a conquered cultural group in a dramatic way