But since Saruman was breeding half-orcs at Isengard, isn't that sufficient evidence that they simply reproduce like other races. Or might they have been male orcs breeding with female humans? And given that in several places Tolkien references breeding orcs I think it's safe to say he meant with females without going into the moronic logic employed by the idiots working on the execrable Amazon series.
We don't actually know how the creatures were created. Treebeard speculates that they're hybrids, but it's never confirmed.
And before you suggest "Saruman was letting his orc allies rape Dunlending women that he somehow acquired without raising any eyebrows," recall that Morgoth (and to a lesser extent Sauron and Saruman) was by our standards a master geneticist with similar capabilities to b-movie scifi mad scientists but with a fantasy aesthetic. He created demons, dragons, vampires, werewolves, etc. Tolkien wasn't a scifi writer or a geneticist, so obviously he wouldn't have the know-how to articulate that, but I imagine that if he did have the know-how then he would articulate that way. For propriety if nothing else. "Created in vats by mixing the essences of different creatures" sounds way less shlocky and exploitative than "abducting women and putting them on rape farms."
Tolkien is not the sort of writer who writes female characters being tortured or demeaned specifically for being female like a lot of writers do. The closest he comes to that is having a handful of minor female characters whose stories are footnotes in the background be forced to marry against their will (
all but stating that they were raped by their husbands), but Tolkien never dwells on violence or torture, especially not sexual torture. At one point he specifies that elves spontaneously
die if they're sexually assaulted, and since they're immortal this means they can just reincarnate later where it's safe. And the closest he ever comes to the monstrous feminine is Ungoliant, who happens to be one of the single most dangerous beings in the legendarium. Morgoth feared being eaten by her! Ungoliant is female and implied to be the progenitor of the giant spiders (presumably parthenogenically), but her monstrosity comes from being made of darkness and hungering to eat everything rather than any act of giving birth.
Tolkien was a hopeless romantic like that. His experiences in WWI and his marriage informed how he wrote his works. It's a far cry from the torture-porn, rape-as-wallpaper, and misogynistic
Handmaid's Tale of Gor-style sick pervert fantasies that characterizes modern fantasy. IMO, we need more men like him, men who aren't ravening sex fiends that hide their misogyny behind wokeness and "but muh realism!".
Sorry for the rant, I just really need to get that off my chest. Again.