We seem to be combining different factors that probably don't fit all that well together. Happiness is subjective. Taste is subjective. Genetics play different roles.
No doubt, the diet of cattle influences their flavor. The microorganisms that are chewing on us during the winter cold season might be able to identify our brand of coffee, if'n they have the communication skills.
Human diets are only one part of a healthy or unhealthy lifestyle. The CDC tells us: "The prevalence of obesity for adults aged 20 to 74 years increased by 7.9 percentage points for men and by 8.9 percentage points for women between 1976–1980 and 1988–1994, and subsequently by 7.1 percentage points for men and by 8.1 percentage points for women between 1988–1994 and 1999–2000." Further, the CDC says: "diagnosed diabetes increased from 0.93% in 1958 to 7.40% in 2015."
We can conflate many different issues. Maybe we should talk about trivial things like hair loss or very serious problems like opioid addiction or why American farmers have such a very high suicide rate.
Diet. Pre- "modern" diets fit within lifestyles and cultures of human societies. These tendencies, habits, choices and requirements for life continued in some cases for thousands of years. Uh oh, we may drift into genetics and evolution!
Anyway, comparing a native of a tropical Central American environment with a nearly total vegetarian diet to the native of the Arctic with very little opportunity to harvest wild plant foods let alone, grow a garden, is problematic. Just what is a "paleo-diet?"
A "modern" diet might be easier for us to define despite the complexity of the food industry. Our food is very much tampered with ... (should I have put that in quotes?) Anyway, this tampering, modifying, processing, and whatever -- begins before the living food organism even exists and goes into the feedlot or incubator or the seed drill. And, it continues ...
At least, we have choices. Some human populations do not.
Steve
Although I don't know that I've ever paid any attention to the diet of the beef that I've eaten. Or.. actually.. that I've even KNOWN what it's eaten.. Is that posted somewhere on the package of 'Food Lion' brand meats????? 
Surprised that he doesn't say "He he" when I do it.
