Mother Jones has an interesting article about how humans might first have learned about the nutritional value of cheese.
Kindstedt, author of the book Cheese and Culture, explained that about a thousand years before traces of cheese-making show up in the archaeological record, humans began growing crops ... for the first thousand years, toddlers and babies were the only ones consuming the milk. Human adults were uniformly lactose-intolerant, says Kindstedt. What's more, he told us that "we know from some exciting archaeo-genetic and genomic modeling that the capacity to tolerate lactose into adulthood didn't develop until about 5500 B.C."—which is at least a thousand years after the development of cheese.
... we now know that the real dawn of cheese came about 8,500 years ago, with two simultaneous developments in human history. First, by then, over-intensive agricultural practices had depleted the soil, leading to the first human-created environmental disaster. As a result, Neolithic humans began herding goats and sheep more intensely, as those animals could survive on marginal lands unfit for crops. And secondly, humans invented pottery: the original practical milk-collection containers.
In the warm environment of the Fertile Crescent region, Kinstedt explained, any milk not used immediately and instead left to stand in those newly invented containers "would have very quickly, in a matter of hours, coagulated [due to the heat and the natural lactic acid bacteria in the milk]. And at some point, probably some adventurous adult tried some of the solid material and found that they could tolerate it a lot more of it than they could milk." That's because about 80 percent of the lactose drains off with the whey, leaving a digestible and, likely, rather delicious fresh cheese.
With the discovery of cheese, suddenly those early humans could add dairy to their diets. Cheese made an entirely new source of nutrients and calories available for adults, and, as a result, dairying took off in a major way. What this meant, says Kindstedt, is that "children and newborns would be exposed to milk frequently, which ultimately through random mutations selected for children who could tolerate lactose later into adulthood."
There's more at the link.
It's fascinating to study the archaeological record like that and work out how a human population that was almost uniformly lactose-intolerant made the switch to become lactose-tolerant, leading to the consumption of gallons of milk per person in today's world (for those who can afford it). I learned a lot from this article, and I'm going to read the book to learn more.