Maybe. I mean, both types of genitals were probably disgusting back then. Sexual attraction is extremely powerful, as is any form of kink/fetish- which it probably took to even consider anal a viable option back then. By our modern standards, even just plain bare skin from back then was filthy and disgusting back then. Even something as innocuous as sucking a nipple from the Middle Ages or earlier would probably make you puke from smell and taste and put you at risk for parasites. What is a disgusting, ushowered, unwiped butthole to us was probably just as viable to an early assman as a modernly clean butthole is now to a modern assman. 

As a side note, I figure that people in the past had much more firm, inoffensive shit than we modernly have.  Even though their exteriors were horrendously dirty by our standards, less frequent meals with less rich foods probably had them pinching twigs more often than mud logs.