Two comments
[1] The Shakers (and not only them, among experiments in communistic communalism) were sexually segregated and celibate. Not a lot of chance to expand -- let alone perpetuate -- their numbers through making children and raising them in the system.
[2] If you haven't yet, you might be interested in reading Ursula K. Leguin's The Disposessed.
[That latter is directed to REB and to Mary Anne, and to anyone else interested.]