Homosexuality (or any non-straight orientation) is not an invention, recent or otherwise. It's a natural part of the animal kingdom and is just as normal, valid and integral as heterosexuality.
Some theorists say that bisexuality is the default state of humanity (with pure heterosexuality being as rare as pure homosexuality) and that the reason so many people have a problem with same-sex sexual interactions is a result of heteronormativity and sexism, the idea that gender roles are rigid and that men who display attraction to other men (or other traits associated with the female gender) are unmanly and therefore inherently wrong and disgusting. That theory would explain why bisexuality, bicuriosity, "experimenting" and homosexuality are seen as more acceptable among women than among men (because of the sexist notions that men who do traditionally feminine things are disgusting because femininity itself is a bad thing, and that same-sex interaction for the pleasure of men is encouraged, while women's pleasure is dismissed).
I don't know if I necessarily agree with that theory as a whole, but I definitely agree that homophobia and the tolerance of lesbianism or female bisexuality are almost certainly the product of heteronormativity, sexism and rigid gender roles.
Your theory is actually very problematic, in many different ways, because it implies that female sexuality revolves around men or childbirth. According to what you're saying, women are straight for reproduction purposes (and are also invariably attracted to male aggressiveness, as if aggressiveness was a male biological trait and not part of the social gender construct. Also you imply that women are biologically attracted to protectors (and that only men are capable of being protectors), ignoring the fact that the whole myth of women seeking protection from men is a sexist construct perpetuated by the patriarchy as a way to sell women that the presence of a man is necessary in their lives because they are incapable of taking care of themselves), and then turn to bisexuality or lesbianism to conveniently absolve men of responsibility for their child (also implying that men "cannot help themselves" when it comes to aggressiveness and other undesirable traits), and that while men are able to explore their sexuality as they see fit without consequences, for women their sexuality is either a form of reproduction (heterosexuality) or birth control (homosexuality), and they switch back and forth as is most convenient for men. It also makes the awful, awful assumption that homosexuality started exclusively with women and then was "passed down to men" as if homosexuality in men was so inconceivable that it needed to be "passed down" from the other gender. That is actually kind of sexist, if you think about it, because it implies that women are solely responsible for homosexuality, regardless of whether you mean "pass down" in terms of genetics or behaviour.
That is... I really would never agree with that theory. It has a lot of problems on a feminist level and it really does not sit well with me as a member of the LGBT+ crowd.
Also I'm actually not a fan of biological or evolutionary explanations for any aspect of society or human behaviour, as it is very, very easy to slide into biological determinism and eugenics (which are quite possible the most horrible misapplications of science I've seen). While I am neither for nor against the genetic explanation for homosexuality/bisexuality/etc (as there are evidence that go in both directions), I think that your theory in particular has a lot of problems that indicate you might want to educate yourself on feminism a little.