Maybe people are suppose to write-in their own observations and experiences with women?
?
No. It means there's nothing we know about women. In other words, we don't know anything about women. That's why the author can't even write anything down.
I think the author is referring to a woman's behaviors though. There are things we do know about women: women conceive and give birth, proliferating life of that kind; women eat foods and drink liquid just as men do. Um...that might be it.
