Mike Eades, on the money wrt physiology and meat eating. If you really want a deep look at this topic, Lierre Kieth’s book, The Vegetarian Myth, will open your eyes. No way to get inside the head of a vegan than via an ex-vegan! And beyond the health issues, Lierre makes it clear that in terms of ethics and sustainability, annual monocrops are the scourge of humankind, animal kind and the ‘earth’.
“At a more general level, this exercise has demonstrated other important points. First, diet can be inferred from aspects of anatomy other than teeth and jaws. For example, an indication of the relative size of the gastro-intestinal tract and consequently the digestibility of the food stuffs being consumed is provided by the morphology of the rib cage and pelvis. Second, any dietary inference for the hominids must be consistent with all lines of evidence. Third, the evolution of any organ of the body cannot be profitably studied in isolation. Other approaches to understand the costs of encephalization have generally failed because they have tended to look at the brain in isolation from other tissues. The expensive-tissue hypothesis profitably emphasizes the essential interrelationship between the brain, BMR, and other metabolically expensive body organs.
I hope you are now armed with enough knowledge to be able to see through these articles and/or charts that are all too common showing how the GI tract of humans is closer to that of a gorilla than it is to that of a cat or some other carnivore. It seems to me that Aiello and Wheeler have pretty thoroughly demolished the notion that humans are actually designed by the forces of natural selection to be vegetarians. Based on the data and the argument they present, it is actually the opposite: we evolved to be meat eaters.
It was our gradual drift toward the much higher quality diet provided by food from animal sources that allowed us to develop the large brains we have. It was hunting and meat eating that reduced our GI tracts and freed up our brains to grow. As I wrote at the start of this post, the evidence indicates that we didn’t evolve to eat meat – we evolved because we ate meat.
Lierre Keith had it right in The Vegetarian Myth:
The wild herds of aurochs and horses invented us out of their bodies, their nutrient-dense tissues gestating the human brain.
If we evolved because we ate meat, why would we want to stop now?”