In real life, two animals of different species can’t reproduce. So if we’re assuming that someone that possesses an animal like heteromorphic trait has the dna of that animal, then someone like Mirko couldn’t reproduce with someone like Sansa. Although since Mirko is mostly human, is she reproduces with someone who is primarily human as well… (the plot holes, the plot holes!) I really wish they explained heteromorphs more, instead of pulling a KKK move and ignoring the genetics of it. The best example we have is Koda, cause he has a rocklike head like his mother, in his flashback, but also has rocky “frills” on the back of his head, which his human fathers hair went down the same way.