All grains are grass seeds including wheat, rice, barley, rye, and corn. Now, oddly enough these seeds are evolved to be eaten but not by us. They are meant to be eaten by grazing animals. The grazers eat the grass but the seeds are indigestible so they come out as droppings in a ready made pile of fertilizer.
Human beings had to figure out how to get the nutrition which is encased in that hard outer shell. First, we just parched it whole in a fire like we do to popcorn today. Ötzi the 5000-year-old stone age European mummified man had a pouch full of parched grain presumably to use as high starch travel rations. Later we learned that we could boil the grains into porridge. After that, we learned we could separate the grain from the shell, grind it up into powder, mix it with water and bake on a hot stone as bread.
No new method of eating grain was invented for 5000 years until the Kellog brothers learned how to flake it so it could be eaten with milk.