NO...people have not eaten grains for thousands of years....actually it’s a fairly recent habit...
“It’s not surprising that grains still make up such a large portion of the calories people in the developed world consume. Our entire food culture has been underpinned by the need to eat grains for thousands of years. Everything about food — our recipes, our tastes, our idea of what’s appropriate for breakfast, lunch and dinner, our idea of an appropriate number of meals per day, our idea of an appropriate quantity of food to eat — has developed and evolved around a grain-based diet.”
http://supplementsos.com/blog/why-do-we-eat-grains/