I just realized that I think my ‘proof’ from the Gemara in Chullin may have been misunderstood.
I was not attempting to prove from R’ Mesharshia’s maskana that Chazal’s knowledge of scientific matters was based on observation. It was from the way he got there. He was trying to figure out a purely halachic sheila: If an animal has an unkosher foot, and then it gives birth, does the non-kosher status of the mother’s foot transfer to the child and in what way? He therefore said, let us figure out what happens when a child is conceived. Does a child’s foot come from the parent’s foot, and therefore the child’s foot will be unkosher too, or does the seed get mixed up, and the foot is coming from other body parts of the parent as well. Later on he retracted his question, because he said that if it were true that a foot bears a foot then every cripple would only bear cripples, and we see this isn’t true. If his science did not come from observation then what in the world was his hava amina and how did he retract it in his maskana?
The answers you are giving are not mistavra and take the gemara out of context. Besides, I have a mefurashe Rambam on my side.
I have a question: Why do you, or some acharonim and maybe even rishonim for that matter, assume in the first place that Chazal’s knowledge was from anything but observation? Where in the gemara is any tanna or amora quoted as saying that his knowledge of the physical world was perfect? For me the most compelling reason to accept what the Rambam says is that why must I bend over backwards to say mind bending and seemingly out of context pshatim in so many gemaras when the most pashute explanation is to simply that their scientific knowledge was based on observation?