There is an interesting interview here on man's proper diet
The Politically Incorrect Diet Part I - Defying our evolutionary heritage
from our inception as a species until the end of our evolutionary glide-path, everyone everywhere ate variations on the same nutritional themes: we hunted and fished, we gathered and we ate whatever seasonally appropriate fruits and vegetables were available. Nothing was cultivated and domesticated livestock was unheard of. Regardless if primal man lived on the African Savanna, the Russian Steppes, the North American Plains, the South American jungle or the Australian Outback, wild animals, fish, shellfish, insects, fowl, eggs and wild fruits and vegetables constituted the sum total of man's available food sources.
There are some interesting comments:
All animals are not created equal. In primordial times, all during man's evolutionary ascent, land animals were outdoor creatures that ate plants, assuming they were omnivores. Nowadays the meat we purchase from the grocery store is obtained from animals that are raised without being exposed to sunlight, animals that are inoculated to prevent disease from ripping through the herd, animals that more often than not are injected with steroidal growth-inducers and fed a substandard diet of poor quality grain. These are sickly, pathetic animals; flaccid, pale and nutritionally impotent when compared their farm raised grass-fed brethren. These animals are chemically poisoned creatures that produce weak, unhealthy and impotent protein.