i should add - there's also the problem of what are all the men of pre-marriage age supposed to do in a society set up under this model? can you really expect a society in which men aren't supposed to be having sex until 30 or later to chug along with no problems? young men will still try to sleep around and this will result in ruined women who will be unsuitable as mates in this more conservative society. your model is basically right but there are still issues.
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