The taking of wives in another country by Rav and Rava is confusing. The Gemara assumes it was for purposes of seclusion.
1) Were the halachos of Yichud in place then? Perhaps these women were housekeepers?
2) Why would a woman place herself in such a position since her marriage chances would then be limited since she will not be allowed to the Kehuna?
3) Where in the Torah do we learn cowives are permitted? We see in the Torah (Acharei) 16:8 "Aravos asheis avicha lo sagalay" which would mean a woman other than your mother, but could mean your father's wife after he was widowed. Adam ha Rishon had one wife. When he separated from Chava things were not too good. Did Moshe Rabeinu have a cowife? Did Yitzchak?
4) Also, when did Rabeinu Gershon forbid the taking of cowives? We are grateful to the Kollel for their answers. It enables us to learn the daf in depth and encourages thinking beyond our study period.
Dov Ber Eliezer Krieger
1) The Gemara brings a machlokes whether or not the Amoraim actually lived with their temporary wives, but is clear that the purpose was marriage, for they were there to create a situation of Pas b'Salo. This is not created by a housekeeper.
2) True, they were no longer allowed to marry Kohanim. However, it is possible that they were already Pasul l'Kehunah or that they wanted the Zechus to be married to the Gadol, if even for one day.
3) Shemos 21:10, Devarim 21:15. As for Moshe and Yitzchak, no and no. See Yalkut Shimoni at the beginning of Shmuel with regard to the two wives of Elkanah.
4) Rabeinu Gershom lived in the Eleventh Century C.E.