I'm interested in the "old men will be more common than old women" part, from the perspective of birthing practices. Is the risk of death by farm injury for men (scythe through the artery, fall from a hay loft, horse kick to the temple) actually less than death by childbirth for women? I think about whether different clans guarded midwifery secrets that ensured greater longevity among the women. Also, in the clan structure you describe, I'd bet that rearing young children would also be the task of pods of women able to wet nurse for longer periods of time, as opposed to exclusively the elders, as after all the baby (up to age 2 or even beyond) must stay by the mother. Otherwise you've got a lot of sickly or dead babies. I've had this idea of writing a story in which the union of wet nurses is the most powerful underground power structure determining a society's continued success and any one family's longterm economic success. Although historically wet nurses were an underclass, akin to a kitchen maid, if the serfs can rise up...