Quote Originally Posted by PArcher View Post
Other big problem with anything X Au Ra/Mi'qote is their tails...this probably prevents crossbreeding in-and-of-itself...
Not necessarily. Even humans, early in embryonic development, have things such as tails and webbed fingers and toes; it's just that they're reabsorbed/destoyed later on for the vast majority of us. There are people out there who are legit born with webbed fingers or vestigal tails. I'd imagine in Eorzea, such cross bredding cases might cause issues, for example something like a Hyur being born with a small vestigal tail, or a manx-like Mi'qote. Not every major difference would automatically make every embyro non-viable, but I will say it's highly likely to be a factor, and I am of the mind the rareness of Hybrids in this universe isn't soley due to cultural taboo, and that chromosomal differences play a role as well.

Take breeding of Donkeys and Horses, who have different numbers of chomosomes. A mule is easier to produce than a hinny, and they are differences between them, even though the only difference at the breeding level is the parent's genders. The different physiology in the various races of Hydaelyn might end up with similar results among potential offspring; not all embyos are viable, some pairings may have higher conception rates (and possibly related to parent's gender), and the final offspring may very well end up sterile.

To add to that, physical size between pairings may not even be a major factor in viability in and of itself. Take the Savannah cat; a serval is about twice the height and weight of the average domestic cat (maine coons and norwegian forest cats notwithstanding). The difficulties in breeding an F1 Savannah come not from sheer size difference, but from the different gestation periods (combined with pickiness with mates). So an offspring between a Roe and Lala may not necessarily be out of the realm of possibility by sheer size default, for example.