So when did the concept of gender even start to come into things? As I'm assuming that it wasn't really a thing until relatively recently?
Being able to make a distinction between sex (biological) and gender role (culturally & historically constructed & changeable) is central to any feminist critique of culture& society (patriarchy).
There's no clear originary point of the making of this distinction - Mary Wollstonecraft (in 1792) and John Stuart Mill (in 1868) both start describing what we'd now call 'conditioning' or 'socialisation' - they noticed that women were 'trained' by our society to act in certain ways which made it look as though because women had babies, therefore they were "naturally" the carers, and the nurturers, for example.
Heres Mill, with his wife Harriet Taylor, in The Subjection of Women on socialisarion:
All causes, social and natural, combine to make it unlikely that women should be collectively rebellious to the power of men. They are so far in a position different from all other subject classes, that their masters require something more from them than actual service. Men do not want solely the obedience of women, they want their sentiments. All men, except the most brutish, desire to have, in the woman most nearly connected with them, not a forced slave but a willing one, not a slave merely, but a favourite.They have therefore put everything in practice to enslave their minds. The masters of all other slaves rely, for maintaining obedience, on fear; either fear of themselves, or religious fears. The masters of women wanted more than simple obedience, and they turned the whole force of education to effect their purpose. All women are brought up from the very earliest years in the belief that their ideal of character is the very opposite to that of men; not self-will, and government by self-control, but submission, and yielding to the control of others. All the moralities tell them that it is the duty of women, and all the current sentimentalities that it is their nature, to live for others; to make complete abnegation of themselves, and to have no life but in their affections. And by their affections are meant the only ones they are allowed to have—those to the men with whom they are connected, or to the children who constitute an additional and indefeasible tie between them and a man. When we put together three things—first, the natural attraction between opposite sexes; secondly, the wife's entire dependence on the husband, every privilege or pleasure she has being either his gift, or depending entirely on his will; and lastly, that the principal object of human pursuit, consideration, and all objects of social ambition, can in general be sought or obtained by her only through him, it would be a miracle if the object of being attractive to men had not become the polar star of feminine education and formation of character
from the Project Gutenberg version: Subjection of Women
And I love this paragraph, where Mill & Taylor point out that we've only ever lived under patriarchy - so its superiority to other ways of running the world is merely theoretical:
The least that can be demanded is, that the question should not be considered as prejudged by existing fact and existing opinion, but open to discussion on its merits, as a question of justice and expediency: the decision on this, as on any of the other social arrangements of mankind, depending on what an enlightened estimate of tendencies and consequences may show to be most advantageous to humanity in general, without distinction of sex. And the discussion must be a real discussion, descending to foundations, and not resting satisfied with vague and general assertions. It will not do, for instance, to assert in general terms, that the experience of mankind has pronounced in favour of the existing system. Experience cannot possibly have decided between two courses, so long as there has only been experience of one. If it be said that the doctrine of the equality of the sexes rests only on theory, it must be remembered that the contrary doctrine also has only theory to rest upon. All that is proved in its favour by direct experience, is that mankind have been able to exist under it, and to attain the degree of improvement and prosperity which we now see; but whether that prosperity has been attained sooner, or is now greater, than it would have been under the other system, experience does not say