What exactly does 'natural' mean to you? Is drinking milk somehow alien behavior that breaks laws of nature? You might find it interesting that most animals are unable to digest milk after a certain age. They lack the enzymes to break down the lactose. There are also humans who have this inability. They are called lactose-intolerant. Humans have been drinking milk for so long that the mutation that allows us to drink milk past our infancy has spread throughout almost the whole human population. Why do you think that it is permissible to extrapolate what is natural human behavior from observing animals other than humans. How is it unnatural if it has been our natural behavior for tens of thousands of years? Because all Americans are fat, wealthy pigs. Right? No one ever goes to sleep hungry in America. Right? No one can ever appreciate food in America because we're all such gluttonous pigs. Right? No one ever works hard for their food in America. Right? No one hunts for their food. Right?