Some people say that our anatomy is closer to that of an herbivore and that we don't need meat. Others say we would never have evolved a larger brain with-out the extra protien from an omnivorous diet. Which side is correct?
Great question as always. You are really asking about the need for meat long term over many millenia and the effect of that on brain development, rather than whether an individual human can live without meat (the answer is obvious). We know from rodent studies that chronically restricting protein intake over a number of generations does indeed reduce brain size and its development. Whether the converse is true is debatable and I suspect will have to stay conjecture since I do not see how it can retrospectively be proved or disproved.
Do others have comments/thoughts?
Certainly if an organism is adapted to have a high protein diet then restricting it will negatively affect its health, though of course that's not the same as 'a lack of protein is bad' - it hardly bothers things like koalas which have little protein in the diet. Certainly some birds are for example very intelligent and not all have high protein diets so it would be hard to argue that protein is essential for intelligence.
I would say that while our anatomy might be closer to that of a herbivore than a carnivore - we are not herbivores but omnivores. Those canines and incisors (our front teeth) are far closer to those of carnivorous animals than herbivores while the molars (back teeth) are more 'herbivorous' looking. In short we have a genuine mixture a good indication that we are adapted to an omnivorous diet. Of course that's not a total indicator of diet (look at pandas - very bear-like dentition [obviously] but are primarily herbivores) when you take into account things like our reduced appendix (which is large in herbivorous animals) and of course the fossil record of ancienct humans killing and eating animals. Taken together the evidence points to an omnivore and if anyhting I would say errs on the side of carnivory - you don't need specialised teeth to eat meat when you have evolved the ability to cut it with tools and cook it first.
Thanks Dave, to restate ambulocetus's orginal question in a slightly different way - do you think that a high protein diet was needed, or contributed to, man's greater intelligence as we evolved from primates?
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