This is pretty terrible; it reads more like the outline of a novel than a novel itself. Everything is summarized and nothing is demonstrated.
It has the common sf error of treating evolution as teleological, but while its evolutionary theory is nonsensical science, I can't help reading it as a trope for gender. The textual treatment of gender is very flawed -- sort of an easy 60s feminism, I guess, women on a more egalitarian level in society, in the background, but marginalized by the narrative -- but I can't help reading the relationship between Simes and Gens in gendered terms. Simes are perfectly normal people who just don't consider Gen humans and can turn on them and destroy them at any time (depend upon them for sustenance), and yet Gens live with them and support them and care for them -- it's like a really horrible take on misogyny as a social institution. But the gendering is mixed, androgynous -- Simes are much stronger than Gens -- but Gens are bigger and more muscular. Simes' moods and logic are profoundly affected by the monthly Need cycle (the resemblance to menstruation/PMS is actually spelled out by one exchange in First Channel). The books read like an unconscious attempt to re-define some despised stereotypes of femininity as simply human -- by projecting them onto male POV characters and by treating them as gender-neutral in the world-building (again, the narrative and the background world-building frequently impose contradictory results).
Very much of the Id Vortex, I think.