Final answer:
The author was surprised by a cultural practice regarding the duration of breastfeeding, which differs from Western norms. Biological factors, such as lactation adaptation and hormonal regulation, explain why sudden weaning can lead to breast engorgement and leakage as the body responds to changes in breastfeeding patterns.
Step-by-step explanation:
The question is primarily concerned with the duration of breastfeeding practices in different cultures and the biological processes involved with lactation. When the author's Mongolian friend mentioned she had to breastfeed up to a certain age that surprised the author, it refers to cultural expectations that may differ significantly from those in Western countries. For example, La Leche League International reports that the global mean weaning age is around four to five years, although in the United States the weaning age tends to be much earlier, with a mean of nine months according to a random survey.
Sudden cessation of breastfeeding can lead to breast engorgement and leakage due to the body's adaptation to the milk production cycle in response to the infant's demand. When breastfeeding stops, any remaining milk in the breasts will be reabsorbed after about a week, terminating lactation if not resumed. Breasts are initially prepared for lactation during pregnancy and immediately after childbirth, hormones such as prolactin and oxytocin regulate milk production and supply, which continuously adjust to the growing infant's nutritional needs.