‘And where does this study imagine that protein and essential amino acids will come from - the building blocks required for advanced brain development?’
protein contents would have to be combined between sources like grains and legumes in order to be sufficient, abetted by starchy carbohydrates sources like tubers...a satisfying, nutritious diet of this sort is possible, but difficult to adjust to our lifestyles...good point about the water, btw...
plant proteins and chemicals are not going to do it. There is a reason that civilization advanced by leaps and bounds once man changed to a steady meat-based diet. Something in meat that’s just not in plants, as evidenced by the reality that vegans, in general, have less robust immune systems. To wit:
4 Reasons Why Some People Do Well as Vegans (While Others Fail Miserably)
https://www.healthline.com/nutrition/4-reasons-some-do-well-as-vegans#section5