Historically when there weren’t enough women in the group they would raid another group and kidnap women in order to have enough children to continue their group. With cooperation, groups began to trade girls for goods with other groups. It is likely that this caused the decline of matriarchal households, because the new girls were foreign to the group and living in the home with her new husband and the husband’s mother.
And concerning population collapse, it’s possible for a population to disappear if there’s under a thousand isolated people. Disease, inbreeding, loss of crucial knowledge, climatic change, extreme weather, are all existential risks that a small population are exposed to.
Historically when there weren’t enough women in the group they would raid another group and kidnap women in order to have enough children to continue their group. With cooperation, groups began to trade girls for goods with other groups. It is likely that this caused the decline of matriarchal households, because the new girls were foreign to the group and living in the home with her new husband and the husband’s mother.
The reality is much more complex that that.
And concerning population collapse, it’s possible for a population to disappear if there’s under a thousand isolated people. Disease, inbreeding, loss of crucial knowledge, climatic change, extreme weather, are all existential risks that a small population are exposed to.