Hi Dr. Jeffery Tucker, 
The answers to your questions are quite variable. There are probably as many
legitimate answers to your questions as there are subscribers to this list. 

For my part, here are a few thoughts: 
Paleo, hunter-gatherer diets began to be displaced in the Fertile Crescent
about 12,000 years before present. But who knows how long it took to make a
complete shift? Further, these people formed only a tiny part of the world's
population at that time. In some parts of the world, the Paleo,
hunter-gatherer diet persisted in human populations well into the Twentieth
Century. Vilhjalmur Stefansson wrote several books about the diet of the
Inuit with whom he lived for about 11 years early in the 20th Century. 

The agricultural revolution made grain-based foods more affordable to
everyone. Those who cultivated these crops had historically grown them as
cash crops and enjoyed such foods only on special occasions. A variety of
perspectives identify the agricultural revolution in Great Britain at
different times. The Agricultural revolution is usually seen as occurring in
the 18th and 19th centuries following several inventions that made
cultivating, sowing, and harvesting more efficient and less labour
intensive. However, others point to the use of an internal combustion engine
combined with the use of chemical fertilizers as constituting the largest
leaps forward in agricultural production. 

As for the "fast food" diet, there are a variety of ways of seeing that as
well. When I was a child growing up in Canada, after World War II and during
the 1950s, we rarely had money for, or were even aware of fast foods. The
closest I got was a trip to the corner grocery store with a dime that I was
sometimes given by a visiting relative. I could have a 6 oz bottle of Coke
for 5 cents + a 2 cent deposit on the bottle. Then I would have only 3 cents
with which I could buy a dozen jaw breakers or 30 candy coated marshmallow
treats. A decade later saw the arrival of the first A & W drive-in
restaurant in our part of the city. It was soon "The" place to hang out. But
when I talk to people my age who grew up in the US, they were eating A&W
much earlier in their lives, and candy was more commonplace for them.
Further, Fish and Chip places in the UK were already a cultural icon by the
time WW II broke out. To further complicate the issue, I know a few British
citizens who would be most offended by my characterizing fish and chips as
fast food. 

I doubt that there will be much agreement on just what constitutes the
nature or the historical beginning of each of the periods you have asked
about. Nonetheless, the general notion that drives this forum is that if we
evolved eating a particular food, we are more likely to thrive eating this
same food. In broad terms, that eliminates refined sugar, dairy, and gluten.
Some people insist that legumes be completely eliminated from a paleo diet,
while others are less rigid about legumes. Still others argue that only raw
foods are truly paleo, while others harken to archaeological proofs of when
humans harnessed fire (although nobody really knows when we began to cook
our food).  

I think that if we can stick to eating more fresh fruits, vegetables, and
meats, our chances of being close to human eating habits prior to the
Neolithic are pretty good. I hope that my rambling proves helpful. 

Best Wishes, 
Ron
     

Ron Hoggan, Ed. D.
co-author Dangerous Grains ISBN: 978158333-129-3 www.dangerousgrains.com 
author: Get the Iron Edge: a complete guide for meeting your iron needs
ISBN: 978-0-9736284-4-9 www.ironedge.info
author Smarten Up! ISBN: 978-0-9736284-3-2 www.smartenup.info           
editor: Scott-Free Newsletter www.celiac.com

"Objectivity is the prerogative of objects."