No humans were eating grains or beans 150K or 200K years ago. Probably nobody was eating them in any significant amounts even 10K years ago. Grain consumption only really ramped up around 5000 years ago, and many human groups only started eating them much more recently. North American Indians only started eating corn/beans around 1000 years ago.
1000 or even 5000 years is not NEARLY long enough to become really adapted to completely new foods that are VERY different from the normal diet.
"Debunk", indeed.