I was thinking that maybe this virus affecting the Y chromosome was made for population control in the pre-cascade era. If there are less males, then there will be less births. And it's not like everyone is into having multiple wives. Plus as we can see, the only way for the current species to maintain their numbers was by making drastic changes to the mating culture by coming up with the Mating Troupe thing.
Sooo, it's like shoot your load and go.
I can see that, but I also thought it could be a bioweapon. It is (apparently, judging by how alex got it) an airborn virus that doesnt express any symtoms except in the next generation, so it would be virtually impossible to notice it and react to it in time before everyone is already infected. If a robot wants to rebel, that would be a GENIOUS play. Slowly reduce the rate in which humans reproduce and when they notice something is wrong, finish them off. That way no one would suapect a rebelion until the very end.