[Nevtalathiel]

I just read an article in Scientific american about how a certain parasite can only be transmitted in the eggs of the insects it infects. Consequently, if a male embryo is infected from conception with the parasite, the parasite is unable to be passed on. The parasite interferes with the growth of the embryo and makes it female. In some cases the parasite simply kils the male offspring which it infects. If dwarves had a similar parasite which worked the other way round and could only be transmitted in the sperm, this could lead to the gender distortion.