Humans have been eating grains for thousands of years. 

 approximately 15,000 years

and before that, what you think? 

 for some 185,000 years we did not eat this shit 

 Human adaption is slow. Not that slow. That's about 215 generations.

And humans have always been able to digest some starches, such as roots, vegetables, or fruit. We're omnivores. 

 Human adaption is slow. Not that slow. That's about 215 generations.

And humans have always been able to digest some starches, such as roots, vegetables, or fruit. We're omnivores. 

 Okay, I can agree with that. Many people probably can't correctly process seeds.
Or alcohol. 

 alcohol suppresses some of the effects of high blood sugar... i only just learned this recently, it increases insulin response 

 Ah, just searched for that. You appear to be correct. Interesting. 

 Perhaps there's a reason why alcohol tolerance and the ability to process seeds occurs together. 

 yes, beer and seed eating appeared at the same time 

 Ah, just searched for that. You appear to be correct. Interesting. 

 Perhaps there's a reason why alcohol tolerance and the ability to process seeds occurs together. 

 yes, beer and seed eating appeared at the same time