sorry for the late response but here's what i meant by the whale mother issue.
See this whole time we worked under the assumption that fertility in earwa works that same as the way it does on earth, which is why the issue of whale mothers doesn't make sense, but in one line in chapter 2 of the unholy consult Kayutas states that women are soil for men's seed which is why Moenghus's assumption that he looks like Esmenet doesn't make since and also why he look mostly like Cnaiur and not Serwa. Everyone in earwa are their father's children.
in fact rereading the books there is almost never an example of a character looking like their mother, they always resemble their father. if we therefore follow with the assumption that men are the givers of life and women just carry the children to term than the conundrum we've been suffering makes sense. The reason why serwe and theli don't make sense in the face of our knowledge about the whale mothers is not because of some hereditary exception with them being half-dunyain allowing them to still be functional, instead there is no such thing as a half-dunyain. The children of Khellus are full dunyain born to poor soil i.e Esmenet, she is one of the few human to be fertile enough ground to carry one to term, most simply don't or are born deformed, but she is still poor ground for dunyain seed compared to a whale mother. In the case of the whale mothers the reason they can birth dunyain children without them so much as resembling whale mothers is because again children take on their fathers trait not their mothers. As for how whale mothers are made? i'm guessing there is one male germ amongst the duyain that carries the trait for wide hips and short limb and that germ is used to produce more whale mothers and nothing else, women born to whale mother but not having that trait i'm guessing are either made useful or disposed of. When you think about it, early in the series we have multiple people commenting on how khellus looks like celmomas, why is that? for the same reason as all the other people, they are their fathers children.
but one issue has been bothering me since following this train of thought, one splintering issue. the only person that i know of in the whole series to be described as looking like their mother is Mimara, and at first that was a hole in my reasoning. Then it hit me! Mimara does not look like Esmenet, she looks like Esmenet's father. Mimara is not just Esmenet's daughter she is also her sister, both are of the same father, it was even mentioned early in the series that Esmenet's father forced himself on her, Mimara is the child of rape/incest. This whole time the reason Esmi didn't want to tell Mimara the identity of her father is because it's her grandfather, and that realization would only be further heartbreak for Mimara, and in Mimara's mind another reason why Esmenet sold her, and another crime Mimara can levy on her. Worst if we follow that train Mimara is reenacting that very situation with Acha without even knowing it.