I've been watching an anime series called SIMOUN, in which I'm struck by some parallels to Jacqueline's Sime-Gen universe.
SIMOUN takes place in a world where all people start life as female. At the age of seventeen (normally) they choose a permanent, adult sex—just as in the Sime-Gen series everyone undergoes a biological transformation at maturity. Just as Gens look superficially a lot like children, but aren't, women in the SIMOUN universe look like adult versions of the girls all children start out as. One interesting feature of this species, however, is that the change from girl to man isn't near-instantaneous like the changeover from child to Sime. There's a period of transition in which the new adult male looks rather hermaphroditic (with breasts, for example). The big difference between this species and Sime-Gen humanity, of course, is that the girls in SIMOUN get a choice about their adult sex. A child in Jacqueline's universe establishes (becomes Gen) or changes over (becomes Sime) involuntarily. It's also implied that the eventual development into Sime or Gen is determined prenatally, perhaps at conception. Girls in SIMOUN may decide beforehand what choice they plan to make, but nothing is irrevocable until they actually take that step. The universal experience of having been female must surely give men of this species a different view on the world from that experienced by real-life human males.
Another similarity involves the Simouns, the two-seater aircraft for which the series is named. Mysterious artifacts left over from a vanished civilization (there's another Sime-Gen parallel!), they are powered by huge, green gems. Apparently the energy source of these gems comes from human life-force. Each Simoun is piloted by two Sibyllae (an order of priestesses), who first kiss each other, then press their lips to the gem to activate it. Very reminiscent of transfer! A Sibylla, alone among all the citizens of this country, has special dispensation to postpone her choice of a permanent sex. This exception is necessary because only girls who haven't yet changed into adults have the ability to pilot the Simouns. Sibyllae range from preteen children to young women well past the age when they would ordinarily have chosen their adult gender. At the time the series takes place, Sibyllae are encouraged to retain their positions because the country is entangled in a seemingly endless war with a neighboring nation that wants the secret of the Simouns. To the Sibyllae and most of their fellow citizens, the Simouns are mystical, divine devices. Using one or more Simouns to inscribe a Ri Majon, a symbol in the air that produces magical effects, is often referred to as "praying to the skies." The Ri Majons remind me of the Endowment in later installments of the Sime-Gen series. A small minority, however, holds the heretical view that the aircraft are merely machines. As Arthur Clarke famously said, "Any sufficiently advanced technology is indistinguishable from magic."
A Simoun operates best when the two pilots, the "pair," have a deep emotional connection. Because of the desperate circumstances of the war, though, it's becoming necessary to pair up girls who have no such feelings or may even dislike each other. I was reminded of the Tecton bureaucracy in UNTO ZEOR FOREVER.
Another significant difference between the two series is that changeover and establishment confer new powers on the young adult Simes and Gens. In SIMOUN, on the other hand, children (a select group of them, anyway) have the unusual powers, and adults are no more extraordinary than men and women in our own world. It's not uncommon in Japanese anime and manga to encounter this motif of children or adolescents having special gifts they lose upon the threshold of adulthood. For example, in NEON GENESIS EVANGELION, only teenagers within a narrow age range have the ability to form a symbiotic relationship with the giant battle robots called EVAs. I wonder what the cultural significance of this motif is? Or is it only a result of the marketing fact that teenagers are a major target audience for anime and manga, so that child and teen heroes naturally play a central role and are the ones with special powers? That theme appears in Western fiction, too. For example, in the Mary Poppins books, babies understand the language of birds, but older children have forgotten it. In Diane Duane’s Young Wizards series, the newest wizards (adolescents) are the strongest in terms of raw power (but not refined skill).
Wikipedia has a detailed entry on SIMOUN, in case you'd like to get more information than my rough summary. This series contains many provocative elements, and I've only skimmed the surface.
Margaret L. Carter (www.margaretlcarter.com)