That's an interesting thought. I was running last week along the beach and was thinking about how early primates/hominids might have decided what plants could be eaten and what plants should be avoided when I saw a stalk of grass with its seeds/flowers. It seemed clear to me just looking at it that the seeds might be extremely edible, and I wouldn't be surprised if many other hungry hominids(and other herbivores) came to same conclusion. What I didn't know was how recent the first grass was nor did I realize how important it might have been for the evolution of land mammals. Here's an interesting fact about grass I just learned (from Wikipedia[1][2]):

> They provide, through direct human consumption, just over one-half (51%) of all dietary energy;

[1] https://en.wikipedia.org/wiki/Poaceae [2] http://www.fao.org/rice2004/en/f-sheet/factsheet3.pdf