I just read this fascinating article by Kameron Hurley where she mentions that women have always fought in wars, they've just been edited out of history by the men recording events. She links to several interesting articles, among them this one on default settings in SFF (ie, white, male, heterosexual).
Having studied medieval history I have a better grasp than many what life was like during those times. Even so, my knowledge was shaped by the books I read, what my professors thought was important, what was known/believed at the time. In other words, despite 'knowing' what the middle ages was like, I'm constantly learning things I didn't know about the era. That's the beauty of life, learning new things and correcting your beliefs to accept the new knowledge.
A lot of people don't seem to do that though, thinking what they learned in school is 100% truth (it's not, - sorry this is a U.S. example. I'm sure every other country manages to teach half truths and outright lies as well) and there's nothing else to know.
It occurred to me, while reading the above articles, that a great way of educating SFF readers would be to do what many historical fiction authors already do: list their research bibliography at the end of the book and have a short author's note on what's real in the book and what they made up/fudged to make the book work. I've seen several authors do this, and each time it not only made what happened in the book feel more real (truth really is stranger than fiction), it taught me things about history I didn't know before.
The first time I encountered this was with Mary Stewart's Merlin series (The Crystal Cave, The Hollow Hills, The Last Enchantment, The Wicked Day, The Prince and the Pilgrim). I've read all but the last one (which was written more recently, and I didn't realize it was part of this series) and they are fantastic. If you like the King Arthur legends, this is a great series. Anyway, I remember getting to the end of The Crystal Cave and learning what the real legend was and how and why Stewart played with it. Similarly, The Wicked Day took a VERY different interpretation of Mordred's story than is generally portrayed and her explanation of why she made the decisions she did was fascinating.
The only other places I remember seeing something similar was in Orson Scott Card's Pastwatch: The Redemption of Christopher Columbus (for an SF example) and Michael Ennis's The Malice of Fortune. M. J. Locke had a quick note about the real program she based one of her programming languages in Up Against It on, which was cool too.
I think it would be a great opportunity for both readers and authors for authors to have a section at the end of the book that gives them the chance to mention some of the research they did for their book. The things readers could learn! Even in just a few paragraphs. And with books to refer to if they don't believe you so they too can expand their understanding of history (and perhaps open their eyes to truths they otherwise can't/won't see).
I'm (slowly) reading a history book called Ancient Inventions by Peter James and Nick Thorpe. It's organized by theme rather than period or geographical location, so it's easy to see who had discovered what, in relation to everyone else. And it is fascinating. Modern people have such a skewed grasp of history and what our ancestors were capable of. We short change them in so many ways and on so many topics.
It would be great to see fantasy books (and SF when relevant) reflect more of what history was actually like. And perhaps adding an addendum of 'this is what's true' would help educate readers, making them less likely to question similar historical accuracies the next time they encounter them in books. Because the only way to change beliefs is to educate people into new ones. And the only way to show the real contributions of women in the past is to represent them accurately, and then make readers understand that they were accurate portrayals.