Traditional cultures that we can observe today still exhibit good health even with a limited range of available plant and animal foods. NO, the Inuit don't eat only blubber - they have some selection of local vegetation that also bolsters their diet. The Kitavans function well on a variety starchy tubers, with a modest addition of fish and occasionally: pork. In other words, as long as you have complete animal protein sources, it would seem that other plant additions are gravy, and you do not really need a huge variety (or at least as huge as conventional wisdom dictates) to achieve very good health.

There is probably something to be said, however, for diversifying the colors of whatever vegetation is available/consumed as the differing colors are indicative of different phytonutrients and might offer coverage against vitamin/mineral deficiencies.

I think the main reason to prescribe/endorse variety in the context of paleo is for folks (especially those starting out) who might feel bored. Beginners may perceive paleo as being only eggs, beef, salads, etc. - so the variety laid out in Robb Wolf's Paleo Solution Food Matrix combats those misconceptions.

I read somewhere that the !Kung eat 100-something species of plants and 200-something species of animals. This would of course include insects etc.

One thing to consider though is that instead of eating 100 types of plants, you could eat spinach and save a huge amount of time. Similarly, if you eat pastured eggs and meat and good quality fish and fowl, the nutrient equivalency makes the consumption of lizards and grubs unnecessary from a health point of view.

I'm not convinced paleolithic people ate such a great variety. Eating a new, unknown food would have been very risky. I also think that cooking is an art that developed to make the unpalatable less so. I eat eggs every morning, steak every night, and food is becoming something I do for fuel only. For the first time in my life, having been on paleo for three months, I'm eating to live, rather than living to eat.

Conventional wisdom came about when industrialized society realized that goods like citrus could cure illnesses like scurvy. They rationalized that the best way to get all needed nutrients would be eat a varied diet. And to some extent I agree, assuming that one eats a varied diet of healthy foods. However, pitfalls abound. For instance, I just heard the checkout clerk at my healthfood store talking about how she planned to eat a healthy varied diet including tofu prepared with vegetable oil and seasonings for dinner. Oops!

I think, however, that it is very possible to eat a limited diet that is still totally as healthy as a varied diet, if not more so. The trick would be to completely understand nutrition and what a person's body needs ideally to survive (or to be smart and also get kinda lucky and hit on it with less information). And we would probably also have to know about individual epigenetics. I think over time, we will reach that point where we can say that spinach is good for one guy, but this other guy better eat collards instead, or whatever. And that each of us would not really need to eat a super varied diet as long as we knew what was good for us and ate those things. But I don't think, as a society, we are there yet.

On the flip side, those with severe allergy and gut problems may do better on very simple diets simply because what is good for a sick person is often not the same as what is best for healthy person. When sick, the priority is often to heal the illness asap before worrying about long term slowly progressing nutritional issues. So like many things, the answer to this question also depends on the situation of each individual.

I think a varied diet is excellent. Thinking paleolithically, it's extremely unlikely that societies - when not confined to say, an island- had to maximize the resources available to them. That is- they didn't go out everyday and get a leg-o-venison from the local herd- they'd also throw in smaller/other things, varying with the seasons. (Say, when they were getting to the end of a deer, they might make a deer-and-rabbit stew, if the deer lasted that long.)

That, and if a group of people was nomadic- which from what I understand is likely, even if it was "only" a seasonal thing (summer hunting grounds vs winter, for instance), different food would be available at each location- and even the "same" food- let's say apples- may have a slightly different nutrient balance due to location factors, like rainfall, soil type, etc.

However, I'd also take into account the issues of modern life before believing that you have to/should/whatever eat a varied diet, whatever that may mean. Perhaps you have a food allergy/intolerance (or lots of them), or even something as simple as there being no good spinach-grower near you, or you may even be recovering from an eating disorder. Take those sorts of personal environment factors into account, do what feels best and works for you, and rock on. It varies so much from person to person- I don't think I'd feel comfortable saying "yes, you can limit yourself to X, Y, and Z and that will BE AWESOME."

(and as an aside- I personally think that when transitioning to another way of eating for health reasons (not just weight loss) that an elimination diet, to whatever extent you're comfortable with, is the way to go, and gradually add in things as you sort out what works. Scientific method, n=1, etc etc.)