I think your assertion that havesting grain led to civilization is the most likely hypothesis but, I'm not convinced we started harvesting grain for food. We've discovered cups with trace amounts of beer that pedate plates with trace amounts of bread by 3,000 years. Again, absence of evidence is not evidence of absence but the theory that we brewed beer before we baked bread is well supported. But, just because we may have invented civilization around beer does not make it the cornerstone of a healthy diet.
