Commentary for Yevamot 125:5

"This time, bone of my bones and flesh of my flesh" (Bereishit 2:23) teaching that Adam had sex with each beast and animal and his mind wasn't cooled until he had sex with Chava. Behold, there is a great mistake at the hand of the Rav Chizkuni of blessed memory and of his people who explain the intent of this statement literally - that Adam literally had sex with (God forbid!) a literal sex act with every beast and animal. And heaven forfend to say this about that righteous one, handiwork of the Holy Blessed One, whom the angels trembled before him - that he should have sex with every beast and animal before he had sex with Chava! And that which the Mahar"sha wrote in the name of the Ba'al haNitzachon, that this isn't literal etc. see there - this statement still doesn't sit well with that. It's clear to me that this statement is settled when one perceives that in every species there's male and female -- [Adam] understood in his wisdom that it was made so in order that male and female could mate and produce new life like themselves. He entered a great meditation and investigation: how, from the joining of two bodies, can an entire new creature emerge? When he saw with his eyes that beasts and animals mate, the male with the female, body to body, and the seed of either of them is invisible and imperceptible and unrecognisable, when this conception is in coveredness - then, his mind wasn't cooled with regard to this matter, how a new thing can come from only the union of two bodies. And even though he was very wise, before he'd eaten from the Tree of Knowledge of Good and Evil he had no reach or knowledge or recognition of these matters which are appropriate to sex and desire for copulation, since he hadn't experienced them himself. He would think of angels to settle his mind in this investigation, and his mind wasn't cooled with them until he had sex with Chava his wife. Then he knew that with the union of two bodies a conception is conceived, he was satisfied to understand that from conception the baby emerges as a new and whole creation, like the parent, and it isn't just bodily uinion. And because of this it says "Adam had sex with [lit. came unto] every beast and animal" (ibid.) - that is, he came in investigation and concentration, to know how procreation happens and shall happen. And this line of reasoning can be found in the Talmud.