Reproduction.

People are born either male or female. If a female lives to an extended old age, and is "initiated" through a secret process, she may metamorphose into a bag-mother.

This is how reproduction happens: The bag-mothers collected genetic material from all passing individuals through a process similar to filter-feeding (they have the equivalent of a built-in PCR and can get usuable genetic samples from something as small as an airborne skin cell, though it's customary to make an offer of blood or hair if you meet one.)


Inside the bag-mother, the bits of genes from dozens or hundreds of individuals are mixed together until an extremely cross-compatible and viable combination is created, which becomes the "empty egg". This empty egg does not contain any of the equivalent of "nuclear DNA", but it has a full complement of "organelles", each with their own genetics. The empty cell contains none of the bag-mother's genes.

When an adult female encounters a bag-mother who has an empty cell prepared, she uses her oviceptor to recieve it. Inside her, it is partially fertilized with her own genetic material, and will remain quiescent until she mates with a receptive male. When she finds the male, she uses the oviceptor to deposit the prepared egg into his breeding-pouch, where it will again remain quiescent, until he mates with another male. Then, he will recieve the other male's spermatozoa, and the act of intercourse will also stimulate his own internal genitalia, and the egg will recieve its final two consignments of genetic material, and begin growing in the male's breeding pouch. After almost a year, the mature fetus will then eat its way out of its bearing-father's  pouch.

In the dominant culture, the sex ratio is about four males to every female, and ten females to every bag-mother; however, the numbers of bag-mothers are artificially kept down by the bag-mothers themselves, and a natural ratio might be closer to one bag-mother for every sixteen males.

Offspring are usually raised in a nuclear family by their fathers, with both females and bag-mothers living alone or in small, single-sex groups. Males tend to divide, by early adulthood, into "bearing males", who have sex with females, and "non-bearing males" who stick with other males, pairing off accordingly, and it is considered slightly perverse for males to switch roles within a partnership, although there is no biological reason not to. In some cultures two males and one female will form a stable triad, but it is more common for the bearing male to go out on his own to seek an egg-carrying female when the pair decide to reproduce.