Looking backwards, being able to produce the enzyme lactase seemed to be an evolutional advantage for people from Anatolia and South East Europe 7500 years ago and made it possible to settle Northern Europe. What 'natural' is, seems for me today to be a kind of a success story, beeing told different for different cultures, ages, places.
Let us just having fun, watching old philosophers fighting for majestic dignity for concepts like 'natural';-)
It is just a imagination, how things *should* be. But, every imagination rules only the people believing in it. No one else...
Wherever there is an imagination, today called rule, there will be poeple trying to make you follow them.
But not everyone believes...;-)