Lots of good ideas in this thread. I have pondered and researched this subject for years. This is what I’ve come up with:
Our ancestors from 10 million years ago (actually much longer but my research starts here) until a few million years ago predominately or entirely ate vegetation. The easiest way to explain this is that proto-humans were very poor at hunting as they had no tools; no spears, knives, or even fire to chase animals off of cliffs. They were also very poor at stealing other animals’ prey. Imagine small proto-humans taking a leopard’s prey from her. Proto-humans probably ate meat when the opportunity presented itself. Like other apes today, that would include small amounts of insects and other small animals.
Some millions of years ago, when we became masters of fire, and much more recently when we became masters of tools, we became more daring in taking other animals’ prey.
Some tens of thousands of years ago, we began eating a lot of meat. We were more effective at communication. That combined with spears and fire we were more effective at hunting.
Fire was important because we are prone to parasites and diseases from raw meat. How could humans be ‘natural’ meat eaters if we have to cook it first? Only after we mastered fire could we become accomplished meat eaters.
Suggestions that eating more meat gave us more calories to grow larger brains, and thereby eat more meat, fails to address why lions, tigers and bears didn’t send a rocket to the moon before we did. No one is clear what caused our brains to grow over the last millions of years but it was not to eat meat. Communication, memory, art, and other intellectual pursuits probably influenced our brain growth – but don’t get arrogant about it. Hummingbirds have the largest brain proportionally to body mass; orcas have a fourth lobe (humans have three). Any way you look at it, their brains are more evolved than ours.
What is clear is that the human body has committed to an herbivorous diet like birds have committed to egg-laying. Changing from plant to animal eating is a huge evolutionary event and not likely ever to take place. We have too many systems committed to an herbivorous diet to expect them all to evolve to omnivorous or carnivorous. The human body tolerates small amounts of meat and small amounts of many things (we tolerate small amounts of narcotics, but that does not make us natural drug users). A tolerance for other things does not change us away from herbivorous. Cats eat some plants but they are anatomical carnivores. Similarly, humans are anatomical herbivores, despite some meat eating.
References to the Inuits who are nearly carnivorous overlooks the early ages that they die. If they were evolutionarily adapted to so much meat, they would not die of kidney failure and other meat-based diseases in their 30s and 40s. Comparatively, vegetarians suffer from the fewest diseases and enjoy the longest lives of any human group.
There are exceptions among individuals, especially in nations with excellent health care. George Burns lived to be over 80 but that has more to do with affluence than smoking cigars. Most smokers die of cancers or heart diseases, most meat eaters die of heart attacks (approx. 50% of American omnivores die of heart attacks, compared to 5% of American vegetarians). George Burns’s long life does not nullify epidemiology.
I trust epidemiology studies. With a trusty protocol, they are more trustworthy than any other science as to what humans should eat. Try this recent study that concludes herbivores tend to have a healthier weight. There are tons of more studies out there. Write to me if you can’t find them.
-Jerry