Historical evidence suggests that early herders were more likely herders were more likely to eat their cows than drink their milk. At that time, most people could not digest cows milk. It became strong and healthy. Their babies often survived because they drank cows milk, which is full of protein, fat, and vitamins. In addition, humans who were abie to digest milk produced more children than those who could not and, as result, passed on their genes for milk digestion.