Breast milk production is a supply and demand process, the breasts will eventually stop making milk, and the milk already in your breasts will dry up once there is no longer nursing, pumping, or hand expressing.
For women who don't breastfeed at all, their body begins to secrete prolactin inhibiting factor (PIF) which gradually shuts down milk production
Engorgement, or when your breasts are painfully overfull with milk, can happen if you're producing breast milk, but the baby is drinking infant formula.
A population that has been isolated, especially a smaller one, could have a high level of homozygosity and therefore not a lot of genetic variation. Gene flow between such populations can increase the level of heterozygosity, and therefore up genetic variation.
