First off, I really enjoyed reading this book; in my opinion it does a far better job of presenting an alternative view of gender than Left Hand of Darkness did. I don't know that I'd necessarily want our civilization to evolve in this direction gender-wise, but clearly Oankali society functions quite smoothly even with a lack of duality. The message is that this kind of functioning is possible for us. Lilith's Brood is a feminist work in the best sense because it promotes and presents a model of true gender equality.
Interestingly enough, the ooloi or "third" gender, who are both male and female integrated, seem to wield most of the power and influence in Oankali society, They take the primary role in procreation and are respected as "treasured strangers" (pp.106). The female Oankali follow just behind them in status, and the males are actually the calmest and most passive. Ultimately, however, an Oankali's gender is of little consequence; though ooloi, those of the gender that would be most unfamiliar to humans, are the ones specifically bred to work with humans.
The structure of Oankali society forces the reader (and the human characters) to confront and accept functional androgyny, and possibly even respect it. It is interesting that even with this degree of control and extra ability, ooloi are still called "outsiders"; perhaps to gradually get the reader audience used to such an idea? I'm not certain.
I loved how among the Oankali, sex is not demonized, it is embraced, and yet made very scientific at the same time. Sex is "shared" rather than being "had". Possession has nothing to do with it; the experience is either sensual and about pleasure, or neutral and merely biological. The process of maturing sexually has an almost-sacred significance and is referred to as a "metamorphosis". Oankali do not have a separate set of sexual organs; sensory arms are "very flexible, very versatile, but only another limb" (pp.110). Oankali do not struggle with sexuality and obsess over pleasure to the same degree that humans do, and yet, it is what they live for in a way.
The only part of the gender model in this book that maybe doesn't work so well is the "demonizing" of the human male. I'm sure that most human men probably would go a little bonkers after not having sex for months, but I doubt that it would drive them all to violence and total dehumanization of women in their minds. In other words, Paul Titus bothers me. It's interesting that the Oankali treated two humans the way that we treat animals today; put 'em in a cage and wait until they mate. However, what do animals do if they don't want to mate? They just don't! No killing or injury involved. I think that human men are being deliberately portrayed as "out of control" but it's an unfair generalization.
There is a conversation between Lilith and Tate Marah, the first woman that she Awakens, where many interesting things show up:
"Who are you Awakening?"
"Leah Bede and Celene Iver."
"Two more women? Why don't you wake up a man?"
"I will eventually."
"You're still thinking about your Paul Titus, aren't you?"
"He wasn't mine." She wished that she had not told Tate about him.
"Awaken a man next, Lilith. The guy who was found protecting the kids."
"On the theory that if you fall off a horse, you should immediately get back on?"
"Tate, once he's Awake, he stays Awake. He's used to ordering people around. He can't save us or protect us but he can damn sure screw us up."
"So what, you're going to wait until you can Awaken him to a kind of harem?"
Tate seems to be driven by typical female desires: the wish to be protected, and sexual desire. Lilith is thinking of the whole group and who will be the most useful, not worrying about her own ability to function sexually. However, they are almost turning some tables and treating the man in question like an object, an animal who would be unable to control himself simply because he is outnumbered by women. This is an interesting experiment to look at, but it is basically reverse-sexist, and probably wouldn't work so well in our human society.