There's no one paleo diet -- there are many of them. They make no sense, but I'm sure you can find a lot of info on them. The theory behind this diet is that some time in pre-history humans ate mostly protein. That was never the case except in places where there was nothing else to eat, such as in very cold climates. Humans have always eaten mostly plant food if it was available except for the very wealthy in modern societies, who eat too much meat. High protein diets are a fad, but the statistics so far have not supported them long-term either for health or weight loss, but in the short term they can be valuable for losing weight and if you're trying to build muscle they can help with that as well, but that's not a health issue. Every time researchers dig into this, they still come up the same place -- the societies with the healthiest, longest-lived, and least obese people eat a diet high in veggies, fruits, grains, and moderate amounts of animal protein. Americans in general eat pretty high protein diets to begin with, though the protein has traditionally been high fat pork and beef. Personally, I think it's all marketing, but I know there used to be someone who is no longer on this forum who didn't follow one of these diets but always recommended it. Here's how silly this gets -- recently at my local health food store there was a product that was a "paleo" waffle alternative, claiming it was "plant-based" waffles. The main ingredient was yuca, a starchy tuber eaten in the countries south of Mexico, which has little nutritional value. But the funniest part was the "plant-based". Waffles are, of course, made of flour, which is, at my last count, made of plants.
I agree with Paxiled that there isn't a single Paleo diet... the so-called Paleo diet is based on the hunter-gatherer types of people and the food they ate depended on the food they could hunt and/or gather at a given time. In some areas that food consisted mostly of plants and very little meat, while in other areas (think Alaska, etc), a fish based diet would be prevalent.
Food was seasonal and during times the best food was plentiful, that's what was eaten the most, but when that food wasn't available, almost anything was eaten to prevent starvation. There was no way to preserve food, so it was eaten as it was gathered. New plants were grown from seeds strewn by the wind, birds, etc.
Studies have shown that it's possible to have too much protein in the diet and I can attest to that, myself, since my doctor had me on a high protein diet for nearly a year and instead of losing weight, I gained nearly 15 lbs...
I've tried a ton of "diets" over the years, and moderate protein, low carb and higher fat worked best for weight loss, but I think we all have to find the eating plan that works best for us. And of course, we can't leave out exercise. I know many say that diet is 80% of weight loss, but I can cut calories and if I don't exercise, I still won't lose weight. It doesn't have to be strenuous exercise, I do have to exercise.
Love you waffle story, Paxiled... I'm with you - I always considered waffles as plant based.