or, could it possibly be, that ‘lactose intolerance’ (or the fashionable claim of having lactose intolerance) is more widespread in populations outside those of Northern European descent, so less dairy is being consumed by a specific population that is producing fewer children?
” According to a May 2002 article in the “American Family Physician,” some ethnic groups have high levels of lactose intolerance including up to 100 percent of Asians and Native Americans, 60 to 80 percent of blacks and 50 to 80 percent of Latinos. Conversely, only up to 15 percent of those with northern European ancestry have symptoms of lactose intolerance.
“Approximately 65 percent of the human population has a reduced ability to digest lactose after infancy. Lactose intolerance in adulthood is most prevalent in people of East Asian descent, affecting more than 90 percent of adults in some of these communities. Lactose intolerance is also very common in people of West African, Arab, Jewish, Greek, and Italian descent.
“The prevalence of lactose intolerance is lowest in populations with a long history of dependence on unfermented milk products as an important food source. For example, only about 5 percent of people of Northern European descent are lactose intolerant.
https://ghr.nlm.nih.gov/condition/lactose-intolerance#statistics
https://www.foodbeast.com/news/map-of-milk-consumption-lactose-intolerance-around-the-world/
Cheese, esp. the harder types, has little or no lactose. Which is why it is popular on low-carb/keto diets.
Aging breaks down lactose I believe
The more you age it, the less lactose there is in it.