>>3586483Okay, lemma put in a way you'll understand a bit more easily:
There are two chromosomal types in the human body: X and Y. Since they are codominant traits only 2 types combinations can exist of them: homogeneous or heterogeneous. Since YY is an impossible combination by natural standard only XX and XY remain viable.
But when you have a third chromosome added, it's not a new gender, it's a disease; a differential from the norm which is detrimental to health the same way redundancy is detrimental.
Would you say that a person with Down Syndrome is "a new trisomy"? No, it's a goddamn genetic disease, not a helpful but rare evolution
