I cannot think of a single society that did not know that women got pregnant and gave birth. If you study anthropology every society in the world has or has had roles defined by sex.
True. Every human society past and present has understood the sex binary and as far as I'm aware every society has also ascribed specific social roles to the two sexes. Some societies have 'third genders' for gay men, which is a way of tolerating male homosexuality by pushing gay men out of the social category of 'man'. See the Hijira of India and Pakistan, the Muxes of Mexico, Thai Ladyboys, the Fa'afafine of Samoa.
But these 'third gender' males are not understood to be actually women. That's why they have a separate word to define them, and the social rules governing their behaviour are very different (less restrictive) to those that apply to women. The claim that transgender males are literally women is unique to the modern Western trans movement.
One thing trans activists avoid mentioning when they weaponise third genderism is that 'third genders' in past and present non-Western societies are almost exclusively male. The societies in which they arise are invariably patriarchal, with strict adherence to sex roles. Unlike men, women in these societies aren't usually granted the opportunity to opt out of their gender. 'Third genders' for women are very rare and tend to arise only under extreme circumstances, such as the Sworn Virgins of Albania, where blood feuds so reduced the numbers of men that many families found themselves without a patriarch or male heir, and women were obliged to step up, by declaring themselves 'not women'.
This also points to the inherent conservatism of third genderism, in that it preserves sex roles by declaring that anyone who steps out of theirs is not really a man or woman at all. My understanding of the 'Two Spirit' tradition in some Native American societies fits into this broad pattern of third genderism being essentially a way for a male-dominated society to cope with male homosexuality. Most nations that did have Two Spirits recognised them only in men (although a few also recognised sex-role non-conforming women), and according to this piece, Two Spirit people were found in patriarchal tribes like the Lakota, but were unknown among the more egalitarian Iroquois. (I'm happy to be corrected on this by someone who knows more. The piece I link to above is well written but unfortunately not referenced, so it might contain some inaccuracies.)