I think that the Cavemen approach is flawed, because the food available at that time was limited by the primitive level of technology. Later on man was able to access important food sources through the discovery of new technology (i.e. fire), which are mostly high value foods such as potatoes and beans, which are important to human survival.
What I mean to say is that potatoes and beans and such are still whole, natural and valuable foods, however in their raw state they are poisonous and they are made edible by cooking, which broadens the spectrum of available food for humans and therefor increases their chances for survival.
Cooking meat also increases the chance for survival, because it kills parasites and bacteria that are very dangerous to us, so in this case technological development again increases survivability by altering raw food.
What is important though, is the fact that we are still dealing with whole foods.
Today food is often divided into it's micro-nutrients, like starch, protein, fat, vitamins, minerals etc. , some people tell you you should eat more of that or more of that, though usually you are not told to eat less of anything, because then someone would make less money. So you're told to eat less "saturated fat" what this actually means is that you should eat less meat and dairy, because those foods were naturally scarce in the past, which means that it makes sense that you have a strong craving for them as they contain nutrients that historically were not easily available, such as iron or calcium.
Today however there is an abundance of all foodstuffs, which means that you have to control that craving as it no longer serves the purpose of directing you towards a scarce source of nutrition.
In the past the environment dictated to you what food was available and your instincts and desires developed according to what was available, today this has changed, as all food is available in abundance your natural sensors so to speak, fail and it becomes necessary that you use conscious thought and willpower to resist your instinctual cravings to a certain degree. For example you crave fat and protein, because those things were historically hard to come by, but today you have to resist that craving because the food you are craving is no longer scarce and you will overeat consistently.
After a certain point processing of food becomes detrimental to human health, exemplified by the extraction of pure starch (white flour) from grains and such , which was based on the assumption that there were only three nutrients, starch, protein and fat and that by removing the "waste" and just keeping the good stuff the food could be more efficiently used by the human body. Of course this was wrong, as we now know that we actually need the waste (the fiber) for various processes in our body, not to mention that it helps to keep us slim by increasing volume of the food in our stomach and also helps with balancing blood sugar because the sugar is absorbed into the bloodstream less fast.
So I think we can say that one should focus on eating whole foods, and, since humans are omnivorous, eat as much species as possible, but should certainly not limit oneself to foods that are only available raw, as that would severely limit the amount of species and therefor nutrients and would in a natural setting decrease survivability, which would in turn be unnatural in the first place because it would endanger evolutionary success. Though food processed beyond the basic level (heating) should be avoided because it's nutritional balance has been altered in unnatural ways which makes it potentially harmful to the human body.
The most difficult part seems to be the balancing of food, as now we have everything available in basically infinite numbers. I think we should look at what was naturally scarce and what was available, and if we do that then we see that the classic food pyramid actually gives a fairly good picture of that, most available were starchy foods such as roots and grains, next are fruits and berries (those are easier to come by but they can't be stored well and are usually low in energy, so grains are superior in terms of assuring sustained survivability where subsistence agriculture is present.)
Meat is difficult to come by in most places and requires high amounts of energy input (for farming) or high amounts of individual energy input for a relatively low success rate (hunting), without conservation methods it also quickly perishes, so meat was certainly a rare and special dish historically, which shows why it is no wonder that eating meat every day is bad for you.
Eggs are probably better than meat, as those are fairly easy to collect.
Raw sugars are not available in nature at all except as honey, which means that one should not eat those at all (which can be done, even if it seems impossible for you now, once you've gotten rid of them you wont miss them.)
Dairy is a special case, as the ability to digest it is mainly an evolutionary adaption to the low amount of sunshine in Nothern Europe and other places (I still cant eat most of it even though I live there.) However historically dairy products require quite the amount of work to produce, as they require you to keep animals and feed them, which means that they were probably not abundant in the past and should not be eaten in large amounts, which also corresponds with what science knows about the actual composition of dairy products.