I have been trying to dig up research on whether or not humans are supposed to be herbivores or omnivores, however the literature is seriously lacking on this subject. It is not difficult to come across pro-vegan websites listing off the many morphological and physiological congruences between humans and herbivores, and disparities with carnivores and omnivores. They all seem to be getting their information from Dr. Milton Mills' paper entitled "The comparative anatomy of eating". It is a fascinating, well-written and logical account that is enough to convince anyone. Well, anyone with an untrained eye.
While I do not refute any of the facts of this article (as an entomologist I do not have the expertise to ascertain its validity), however there are a few crucial flaws that raise red flags for me. First, this article is completely devoid of references. Any good scientific review should include the sources of its information. Even Wikipedia articles come with an often lengthy list of citations.
The second red flag is that this article was not published in a peer reviewed journal. I'm sure we've all heard the sage advice "You can't believe everything you read on the internet". Which is precisely why I try to obtain my information from reputable sources, the best of which is a peer-reviewed journal. For those of you who are unfamiliar, peer-reviewed simply means that the paper has been scrutinized by other scientists (the identity of whom is unknown to the author) prior to publication. This limits the chance that the content is complete rubbish. In other words, quality control.
A little searching reveals that Dr. Mills is in fact a real doctor who graduated from Stanford university, practices in Northern Virginia, and is on the advisory board for the Physicians Committee for Responsible Medicine. This suggests to me that the information in this paper has a higher likelihood of containing accurate information. That being said, I am still disappointed that a published doctor would fail to cite his sources in an essay with profound implications for the vegan community.
All things considered, it is a recommended read. If you're not in the mood for reading, he has concisely summarized all his arguments in a table at the end.
As I was trying to find reputable evidence for the human-herbivore connection, it dawned on me "Why does it matter?" Think about it, even if we were meant to eat meat, the meat we eat now, and the way we eat it, is certainly not how nature intended.
First of all, I don't think anyone will negate that we are certainly not meant to consume the breastmilk of another species, so lets do away with that right from the start.
Secondly, if we were supposed to eat meat, I imagine it would be in the same way that chimpanzees eat it. Although chimps do eat meat, it does not constitute a major part of their diet, nor does it seem that there is a nutritional need that necessitates hunting in chimps, as a group of 10 or more will cooperate to hunt a 1kg juvenile monkey. I will note, that of the great apes, only chimps and humans eat meat, suggesting that this behaviour has only recently evolved, therefore supporting the anatomical similarities between humans and herbivores. A recent reversion to hunting in chimps and humans, paired with the limited presence of meat in the diet, would provide insufficient selective pressure to alter our herbivorous characteristics.
Thirdly, and most importantly, the meat we eat is not natural. Domesticated livestock have been selectively bred for productivity and plumpness. Selective breeding deprives the gene pool of important traits that protect against disease and otherwise improve the health of the animal. As a result, the meat in the grocery store has been filled with antibiotics, not to mention growth hormones, steroids, and other things that I'm sure I'm not even aware of.
From a nutritional point of view, the animals we eat are a far cry from their more robust, wild counterparts. Let's take beef as an example. Beef cattle belong to the same Genus as yaks, making them the closest related animal that is regularly consumed by humans that I could find any information on. A fact sheet found on the DelYaks website informs us that yak meat contains only 3-5% fat compared to 8.5% fat in lean beef or over 12% in a lean t-bone steak. DelYaks also claims that yak meat is a higher source of protein, vitamins and minerals, while having less cholesterol and triglycerides than beef. As an aside, from an environmental and economic perspective, yaks (and the ancestors of cows) subsist totally on grass that is grazed from pastureland, reducing their environmental footprint and costs required to raise them. Which again comes back to the chemicals in our meat: the grains fed to livestock were also produced using pesticides, further increasing their load of unnatural toxins.
The same exercise could be done with chickens, but I think you already see my point. Whether you want to argue that humans are meant to eat meat or not, most people would agree that the way our society eats meat is not supported by our evolutionary past.