Looking at our Past to Gather our Future
I am sometimes asked "Why do you spend so much of your time talking about kindness to animals when there is so much cruelty to men?" I answer: "I am working at the roots." ~ George T.Angell (1823-1909)
The features of human beings, our physical appearance as well as our physiology and anatomy can be understood as an adaptation to our environment, which over time becomes encoded into our dna so that even if or when our environment changes, we still maintain the adaptive appearance and physiology of our ancestors.
Taking skin color as an example, skin color is determined by the amount and type of melanin, the pigment in the skin. The more melanin, the darker the skin. Melanin protects against ultraviolet light waves from the sun. (Wikipedia) Usually people with anscestors from tropical regions and higher altitudes (hence greater UV light exposure) have darker skin than people with ancestors from subtropical regions.
If this is true, by looking at the early humans, their environment, the types of foods they consumed, we can deduce what adaptions were made and transferred to us through our dna. This will inform us as to what our current bodies are designed and equipped to consume, digest and assimilate in a healthy, natural and appropriate manner.
In The Beginning ~ Gatherers, Not Hunters
Though it is commonly thought that early humans obtained their food through hunting and gathering, the latest anthropologists such as David Pimmel, Donna Hart and Robert Sussman are now concluding that early humans were gatherers yes, but hunters, decidedly not. On the contrary, after studying conclusive evidence, they state that humans were hunted, not hunters. We were prey, rather than predators.
In the book Man the Hunted: Primates, Predators, and Human Evolution by Donna Hart and Robert Wald Sussman they share the recent discoveries of human skulls with holes in them the exact size and placement of predatory animals such as tigers and lions.
Vegans then, Vegans Now
From this we can further deduce that if early humans were gatherers and ate mostly like their primate ancestors, then we humans were originally and still are herbivores. We would therefore fare best on an herbivorous diet, completely comprised of selections from the abundance of the plant universe (rice, beans, lentils, split peas, nuts, seeds, sprouts, broccoli, carrots, apples, peaches etc).