Comparative physiology debunked

If people want to follow plant based or plant centric dietary patterns, I really don’t care. I care even less when such people recognize the importance of producing their plant food in regenerative agroecological systems of food production especially integrated systems like pasture cropping, cover crop grazing, and dynamic agroforestry. Why? Because these ways of producing both animal and plants food are the least destructive, require the least amount of inputs, and greatly enhance soil health as well as produce the most nutrient dense food (Montgomery et al 2022).

But where I draw the line is when dietary patterns become quasi religion that zealots try to impose upon others by any means necessary. This includes commentaries like the one in this video clip where a popular vegan advocate claims to use “science” while actually referencing ideas originally espoused and promulgated in the vegan cybersphere by a creationist.

These ideas known as comparative physiology [CP] are widely cited and often repeated in the vegan cybersphere to “prove” humans aren’t suppose to eat meat based on a wide array of physiological factors compared to other meat eating animals. These factors include teeth, gut length, chewing patterns, speed, lack of claws, stomach acidity, etc. These ideas were largely formulated by Dr. Milton Mills in his 1987 treatise on comparative human physiology. Mills continues to champion these ideas. Now does Dr. Mills have a PhD in paleo-anthropology? No, he’s an emergency room medical doctor without any background or understanding of paleo-anthropology.

Mills is also a creationist. So he doesn’t even believe in evolution. Thus comparative physiology is based on the premise that features humans and other creatures now possess are what we’ve and they’ve always possessed from when we were created by God six thousand or so years ago. However, when you recognize evolution and understand paleo-anthropology, you quickly realize that hominin/human evolution has made human physiology quite unique in a variety of ways.

For example as Harvard’s Daniel Lieberman noted in his book, The Story of the Human Body, humans are the only routinely bipedal species without a tail or feathers. Unlike other primates, humans also are not knuckle walkers.  Being routinely bipedal (on two feet), freed up hands and allowed homo sapiens ancestors to become tool users. And guess what? Hominins were and humans are one of the only creatures that also routinely uses tools. In contrast to knuckle walkers like other apes, bipedalism also expanded the range of hominins out of forest into savannas where over 3 million years ago, hominins used rocks to smash open bones to access brains and bone marrow scavenged from other animals’s kills in those savannas as discussed in this below video. The fats from these scavenged brains and bone marrow helped to fuel hominin brain growth.

Then hominins started to sharpen those stones into honed surfaces that they used to slice leftover meat off of those scavenged carcasses. This sliced meat also helped increase brain size by providing more energy dense food in fewer meals. Read this Science article, How sliced meat drove human evolution, for more details.

So bipedalism freed up our hands to use tools, and those tools allowed us access to fats and meats which provided a nutrient dense energy source that led to bigger brains and also the need for smaller colons. And since hominins used tools to pre-process their food before putting it into their mouths, our ancestors also lost the need for massive claws and sharp teeth to tear apart food. Thus comparing the teeth of other animals to humans is silly. Those animals all evolved along different evolutionary pathways. Not to mention, there are a wide array of other meat eating species with very different dental physiology.

Later as hominins further evolved into hunters rather than scavengers, our ancestors lost their body hair and developed sweat glands. Thus our ancestors became persistence hunters literally running other faster animals without sweat glads and with fur to the point of exhaustion. Humans are one of the few animals with sweat glands. Persistence hunting made it possible for hominins/humans to kill swifter animals despite their/our lack of speed. Thus not only did we evolve not needing big jaws or claws, we also evolved without the need to be faster than the prey being pursued thanks to sweat glands.

Funny though, since we originally evolved as scavengers, our stomach without food have a very low pH of 1.5-3. The pH is only 4 to 5 when our stomachs are full of food, Vulture stomachs function the same way. So when vegan evangelicals claim that a human’s pH is higher than other predators, they’re filtering and selectively misrepresenting data as such vegans evangelicals often do. 

Now as our ancestors learned to become better hunters, they also developed weapons as well as ways to preserve (with salt) and cook food. This further increased the energy density of food our ancestors consumed. And again, our hominins ancestors were pretty much the only species to routinely cook food with fire. So are modern day humans.

Note bipedal hominins, that scavenged, migrated to other places following the kills of cave lions & other predators as those animals also migrated for food. These migratory patterns further increased with hunting following large megafauna herds like mammoth now extinct (Ben-Dor & Barkai, 2020). So, contrary to prevailing myths about scarcity, meat was actually quite abundant. Though hominins also ate insects, shellfish & plants when hunts were unsuccessful. Plants were also largely consumed seasonally due to drought or cold weather depending on the places hominins migrated to across the globe. In general, early humans evolved in ecosystems unlike any found today.

Furthermore, hominins, both scavengers & hunters, ate the brains of their kills. Brains, and to a lesser extent liver, spleen and bone marrow, are a very good source of DHA. This offal was a huge energy source. Hominin & human brains largely consisted and consist of DHA. So shellfish & fatty fish weren’t the only sources for preformed DHA (EPA & DPA). Regardless, in paleo-anthropology, the evidence for meat eating is a lot more persistent than that for plants meaning meat eating is better recorded. But hominins still ate plants when in season. Though not by any means, as vegan evangelicals claim, were hominins herbivores.  

Being omnivorous is reflected in our physiology, and more specifically our metabolic flexibility. So for example, we can derive energy from fat or carbs, and our liver can turn carbs into fats (via de novo lipogenesis) and proteins into carbs (via gluconeogenesis) as required. These abilities are also regulated in the pancreas by the production of either alpha or beta cells. Again, a lot of this metabolic flexibility was necessitated by seasonal availability of different foods. This flexibility also allow the homo genus to live in a wide range of environments unlike other primate species confined to specific ecosystems.

This flexibility is why humans can also use fiber, amino acids or ketones to create short or branch chain amino acids to support our gut and intestinal linings (Oliphant & Allen-Vercoe, 2019). This flexibility again is the result of evolving in places where plants or meats weren’t always available. Lucy Mailing PhD, an expert and researcher in the human gut microbiome, explained how ketones support the gut lining in this below video clip:

Needless to note, dietary religion gets very tedious very quickly especially when purported “science”arguments are in fact rooted in creationism rather than paleo-anthropology. This is clearly the case with comparative physiology. So over zealous vegan evangelicals should be embarrassed promulgating such nonsense. But that’s the thing with too many abolitionist and absolutist vegan evangelicals, no matter how many times you correct them or put their out of context stats back into context, they continue to repeat the same half truths & lies ad nauseam. For them “truth” is whatever helps them accomplish their goals. They also seem to follow the idiom that if you repeat a lie often enough, that lie will somehow become a truth. Some are so fanatical, that these lies become their “truths”. So ultimately, in their minds, it doesn’t matter what’s being truthful since for them, the ends justify the means. 

Now the truly sad thing with such deceitful absolutism is that all it does is further division. So rather than find any common ground and work toward common goals to improve animal welfare, mitigate climate change and improve our food system, all absolutism ultimately does is preserve the status quo. And not only does absolutism preserve the status quo, it reinforces the status quo. So absolute vegans ultimately are nothing more than pawns building market share for the patented IP food tech of VC’s, oligarchs, globalists & multi-national corporations. That’s the sad reality 

Well, finally, if you want to read a great book on how human physiology is connected to our evolution and paleo-anthropology, I highly recommend the book I mentioned above by Harvard paleo-anthropologist Daniel Lieberman, The Story of the Human Body. For people who don’t have the time or inclination to read Lieberman’s book, Lieberman has a number of good presentations on YouTube like this one just below:


Montgomery, D.R. et al 2020. Soil health and nutrient density: preliminary comparison of regenerative and conventional farming

Ben-Sor, M & Barkai, R. 2020. The importance of large prey animals during the Pleistocene and the implications of their extinction on the use of dietary ethnographic analogies

Oliphant, K. & Allen-Vercoe, E. 2019. Macronutrient metabolism by the human gut microbiome: major fermentation by-products and their impact on host health.

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