Todd> The usual rule is "no grains," and I do agree that a grain-based
diet is deeply problematic.

If it's deeply problematic, why leave that door even partially open?
Even non-gluten grains contain antinutrients.  And we've discussed ad
nauseum how the peptide structures in gluten grains are so structurally
similar to some human protein structures that autoimmune disease results
from their consumption.  And that's to say nothing of the high carb part
of the equation.  Maybe some people can eat them with no issues, perhaps
they can't.  Why roll the dice on what had to have been a rare dietary
adjunct?

Todd > My view is that hominids relied on food processing technologies
for survival, beginning with their exodus from the tropical forests.

Your use of the term "for survival" seems to imply a Hobbesian existence
for these new prairie beings.  You cannot deny at least that humans fare
very well on food that requires no processing whatsover save a rock
against a skull or a spear into a side.  No doubt in times of scarcity
we searched for alternate food sources -- and had to "process" them to
make them edible.  Doesn't make those food sources ideal.

Todd > The cultivation of grains, of all things, in the neolithic period
makes no sense if people weren't already eating them.

Somebody somewhere came up with the idea of sticking these grass seeds
in the ground and waiting around until they came back up.  No doubt
that person or group of people had consumed the seeds before.  But
agriculture swept the world, coming and going in waves but eventually
winning over the entire world, and found its way to people who had
probably never considered consuming grass seed.