Vegeterian Human?

In my writing I often rely on our distant past of humans to determine what we should eat and how we should behave. The adaptations come extremly slowly, and rapid changes are usually not healthy, if you don't believe then feed your cats cooked cabadge and you will see how long it will live.
There are exceptions however, species that are normally carnivorous develop sub-species that eat vegetables. The example would be a panda bear, or certain apes.
Humans have had the sidekick species that ate vegetables too. Paranthropus boisei who lived 2.3 million years ago in Africa had jaws that were massive by today's standards. The muscles around the face were buldging as in these days the fire was not known for these primitve ancestors or ours. We cannot say for sure how different was their digestive system, the stomach might have been bigger than ours as vegetables have very little nuritional value and take long to digest. Otherwise, we have to assume the they still had the basic ominvore digestive system and did not pass the termite hill, or a bird nest when they found one. They were not vegeterian as we think of it.

Hunter gatherer (or rather scavenger) lifestyle and diet

Ever since university times (Cultural Anthropology major), I was thinking about the lives and the diets of our ancestors. 

After all, the last 10,000 years of agriculture, is just a drop in the bucket comparing with 5 million years of evolution of our body and digestive system.

What is human bipedalism optimized for?

Our ancestors have spent most of their days traveling their territories in search of edible nuts, seeds, plants small animals, and rarely a carcass of the kill. The travel distance was varied depending on the climate, there are hunter-gatherer communities that have to do very little actually for subsistence, maybe few of hours per day, but most likely it was something like 10 to 15 miles per day. We are built for distance travel - search and slow, long pursuits of wounded animals, on the other hand humans are terrible sprinters, slower than almost any animal out there.

What was the diet of our pre-agricultural ancestors?

Our diet was definitely composed largely of VARIOUS seasonal nuts, fruits, edible plants which were on average low in starch and sugars, otherwise we would not develop such craving for sweets, but high in fiber and proteins, in addition a portion of the diet were small animals ranging from insects to rabbits. Yes, for many of our ancestors it was "taste like rabbit" not "like chicken", at least judging by the number of rabbit bones found. Fatty foods were considered premium in every culture. 

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I came across this article, which I found thought-provoking:

Like many New York bachelors, John Durant tries to keep his apartment presentable — just in case he should ever bring home a future Mrs. Durant. He shares the fifth-floor walk-up with three of his buddies, but the place is tidy and he never forgets to water the plants.

Béatrice de Géa for The New York Times

NEW ICE AGE Meat storage for John Durant's paleo diet.

The one thing that Mr. Durant worries might spook a female guest is his most recent purchase: a three-foot-tall refrigerated meat locker that sits in a corner of his living room. That is where he keeps his organ meat and deer ribs.

Mr. Durant, 26, who works in online advertising, is part of a small New York subculture whose members seek good health through a selective return to the habits of their Paleolithic ancestors.

Or, as he and some of his friends describe themselves, they are cavemen.

The caveman lifestyle, in Mr. Durant’s interpretation, involves eating large quantities of meat and then fasting between meals to approximate the lean times that his distant ancestors faced between hunts. Vegetables and fruit are fine, but he avoids foods like bread that were unavailable before the invention of agriculture. Mr. Durant believes the human body evolved for a hunter-gatherer lifestyle, and his goal is to wean himself off what he sees as many millenniums of bad habits.

These urban cavemen also choose exercise routines focused on sprinting and jumping, to replicate how a prehistoric person might have fled from a mastodon.



Resources

http://www.nytimes.com/2010/01/10/fashion/10caveman.html?sudsredirect=true