It sounds like the so called "paleo diet" you are talking about. It's not really scientific. Like hardgain said, survival and bodybuilding is too different things. Also survival and optimal is too different things. It is also a big mistake to try and correlate anceint hunter-gatherer diets to modern times of food surplus.
The reason fat and animal protein was so important was because it gave the biggest bang for the buck. Which means that you feast on it when you can get it but you can by no means get it everyday. High amounts in those times has a differnt meaning than it does today. You want to have a paleo diet then you better eat really small amounts most of the time or else all that high fat is gonna kill you.
But if you want to bodybuild I would rely on modern nutrition. But these are fat loss diets. They have nothing to do with optimal health. I can assure you that high fat in a truly paleolithic diet would have been high saturated fat. The people that promote this stuff are pseudo-scientists who twist facts to promote a dietary view. You want to eat paleo put some insects in your diet. Try to eat only the fattest blubber filled animals when your can get them and eat the whole thing, innards and all. Don't be afraid of eating what you find under a rock either. And forget about the nice mixed greens with balsamic vinegar dressing
One thing I would point out is that so many of the assumptions made are based on the health decline seen in "modernized" tribal societies vs. their original living conditions. Or basically the higher incidence of acute health problems, infections, and lower mortality seen in a shift to an agricultural existence for some populations. Diet can be blamed for some of that but not for everything. One of the BIGGEST difference between the two is OVERCROWDING. Basically the more people you have living in one unchanging area, the better chance you have of getting sick.
Pretty much everything about this kind of "science" is stupid to me. They lump different times, different parts of the world, and different peoples together. Native americans and "cavemen" are viewed as part of the same picture, which is absurd. They ban certain foods that would have been a staple for some people, such as tubers, while promoting others that would have hardly been available at any time. Corn is outlawed although it was a staple at certain times and for certain native americans. It's really rediculous.