Throughout history when any two groups of humans have met the main factor in determining which group prevailed in the violence which almost always occured was the food that they ate. It was primarily a matter of luck in living near a food source that grew in the wild which could be domesticated and grown in such a manner that the ratio of calories to work hours was as high as possible. The main foods which accomplished this were wheat and rice. They originally grew in the wild in Asia and the Fertile Crescent. In North America corn was still tiny and not bred to be huge until relatively recently.
Wheat was able to expand to east and west, to relatively similar climates. The potatoes of South America couldn't so easily expand to the equator and then up into colder climes.
Basically there just wasn't much to work with in North America, in terms of a food that had a high ratio of calories to work hours. The best they managed was sunflowers actually.
In Africa also the options were not as good.
Same idea also held in terms of animals. African animals just weren't easily domesticated. Rhinos and cheetahs? They even tried actually to domesticate cheetahs but failed. There were no horses (zebras can't be domesticated). Now cows. Etc. Same in North America. A buffalo isn't quite as easy to work with as a cow...
Anyway, these cultures which had wheat and rice were able to specialize tasks. Fewer farmers, more beuracrats(sp), and professional soldiers.
Specialization in and of itself is a somewhat 'evil' thing. Furthermore this wheat, it's not actually all that healthy for you. The ratio of nutrients to calories in dark bread for example is roughly half that of what you get from a potato.
But so cultures like the Romans fed their peoples wheat. A crappy diet which probably lowered their life expectancy. But meant they could have a full time force of soldiers who just constantly went around attacking other peoples.
Wheat, especially, is a shitty food. Excuse me for talking about what is and isn't 'natural' but how less natural can you get than this grain which you have to grind up because it's completely impossible to otherwise digest?
One of the neat things that our wheat diet gives us, along with cancer from the resulting lack of nutrients is messed up bowels, as it sticks like glue. Hemorroids(sp), colon cancer... Hemorroids is particularly comical in that it affects a pretty sizable percentage of the population but it's largely a secret. And a primary cause is wheat products. Which are so overwhelmingly prevalent that few people have managed to remove them all and thus notice the role they play.
They also generally make people look like shit. They're fat, dumpy. And from the malnutrition their faces are pale. The food sits in their stomachs relatively like stones causing them to have less energy and generally sit around watching TV.
But they kill good. And it's efficient. Quality of life down the drain. But look who won?
All around us, it's the wheat world. Highly efficient, boring unvaried food, decreased life expectancy and feeling like shit. Other than meat, if ever there were an 'evil' food, it's wheat.
The Celts. They grew a ton of different foods. So many foods they regularly grew which are now lost to us. They had no chance against the Romans of course. Although they were more than a foot taller thanks in part to eating food that could actually properly nourish your body, they did not have a massive professional soldier class.
Joel Fuhrman advocates a diet which tries to maximize nutrient to calorie ratio. He points out that wheat has a bad ratio and starches in general do and should thus be minimized. John McDougal on the other hand (both advocate vegan diets as those are actually the healthiest(sp) way to eat) advocates far more starches. Why does he? Because everywhere he went in the real world he found only people that ate a lot of starches and in his genius he surmised that without all those starches you apparently would just sit around and starve to death or.. at least not have sufficient enery to bother reproducing.. (He actually argued this point with Fuhrman and that was why he thought Fuhrman was wrong.) Among other things he clearly hadn't read Jared Diamond's Guns, Germs and Steel. The reason we see only cultures that eat a ton of starches is because the growing of such 'efficient' foods meant more people could be devoted to killing. And so a more sane way of living was eventually murdered off.
In how we interact with one another and also in how we eat.