It’s an advertising staple:

http://contexts.org/socimages/2009/06/21/feed-fathers-man-food/

http://contexts.org/socimages/2009/05/20/for-men-only-vintage-campbells-soup-ad/

“Low-carbohydrate-high-protein diet and long-term survival in a general population cohort by Antonia Trichopoulou of the University of Athens Medical School published in the on-line version of the European Journal of Clinical Nutrition found that “…higher intake of carbohydrates was associated with significant reduction of total mortality, whereas higher intake of protein was associated with nonsignificant increase of total mortality… with respect to both cardiovascular and cancer mortality.”1

This study involved 22,944 healthy adults, under observation from 1993 to 2003, whose diets were assessed through questionnaire. The authors make a point of saying proteins of plant origin are not the problem and “…are generally considered innocuous, if not beneficial, to health.”

[Summary:] “…animal products shorten life—plant foods will help you live longer.”

http://www.drmcdougall.com/misc/2006nl/dec/fav5.htm

Anyway, Sue I think humans evolved primarily as animal eaters specifically fat eaters. Plant foods were seasonal foods of opportunity, not staples. I found an article I don’t have time to look up that shows based on our brain to body ratio and the amount of plant foods available that animal fat was the best bang for our buck and was mandatory to provide the calories our brains need to function. I think this article was on BeyondVeg.

As for eating plants, basically all plants have phytotoxins that bind minerals we eat and make them unavailable. Our digestive systems have no real way around this. Traditional cultures overcome this by sprouting seeds or washing them and undertaking various other preparation methods to cleanse the plants of their poisons. Clearly diseases like celiac and diabetes show that concentrated sources of sugar are very late additions to the food supply, and poor ones at that. Meat on the other hand is no problem and can be consumed raw without any issues.

Finally some anthropologists believe that language and our sense of time evolved out of a need to discuss and coordinate large game hunting activities. Since our apelike ancestors did not provide the physical strength or the physical tools to overcome prey we used organization and clever minds to create technologies to achieve success. These minds needed to communicate and understand each other and needed to be able to comprehend that some events happen before or after other events and talk about them. If it were not for our largely carnivorous nature I doubt we would be here today.