You have a source to read that up? At least in 452, they (some) were already pretty sure about her being virgin.
Dioscorus then moved to depose Flavian of Constantinople and Eusebius of Dorylaeum on the grounds that they taught the Word had been made flesh and not just assumed flesh from the Virgin and that Christ had two natures.
Mary was not virgin until they changed the story later around A.D. 300, during the Romain Catholic Church.
Oh. Damn. I only heard the story AFTER 300AD. I was late to the game, I guess.
You have a source to read that up? At least in 452, they (some) were already pretty sure about her being virgin.
https://en.m.wikipedia.org/wiki/Council_of_Chalcedon