Here is an article that very briefly sums up a few anatomical similarities and differences between carnivores, omnivores, herbivores, frugivores, and humans.
https://www.uiargonaut.com/2018/11/09/humans-are-herbivores/
Here is a comment I found on that article that sites a whopping 40 anatomical differences between carnivores and humans, as well as similarities between humans and herbivores and especially between humans and frugivores:
“From: Humans Are Herbivores*
A Scientific Case For Veganism
~Adam Riva
40 Anatomical Features That Classify Humans As Herbivores
There are several types of features that help biologists determine the feeding behaviors of animals. For instance, digestive abilities, “hunting or gathering” abilities, reproductive habits, locomotive abilities, and circadian rhythms are all taken into consideration. To illustrate this better, here are two examples. Stomach acidity differs greatly between herbivores, omnivores, and carnivores, which would demonstrate an animal’s evolutionary adaptation to digest simple carbohydrates such as fruit or complex proteins and fats such as meat. Additionally, whether or not an animal has claws will likely determine if it uses them for hunting or not.
It is important that a conclusion is not reached after reviewing one or two data points. Rather, we must make our conclusion by assessing the totality of all available data. To conclude humans are anything other than herbivores is to ignore the following striking pieces of evidence.
1. Carnivores have facial muscles that are reduced to allow a wide mouth gap to swallow large chunks of meat or entire animals whole. Omnivores’ facial muscles are also reduced. However, herbivores and humans have in common well-developed facial muscles for chewing plant matter.
2. Both carnivores and omnivores have a jaw angle that is acute. Both herbivores and humans have an expanded jaw angle.
3. The location of the jaw joint in carnivores and omnivores is on the same plane as their molar teeth. The location of the jaw joint in herbivores and humans is above the plane of the molars.
4. The jaw in carnivores and omnivores is designed to shear and has minimal side-to-side motion. The jaw in herbivores and humans is very dextrous and moves side-to-side and front-to-back.
5. The major jaw muscle in carnivores and omnivores is these temporalis. The major jaw muscles in Herbivores and humans are the masseter and pterygoids.
6. The size comparison between mouth opening and head size is very exaggerated in carnivores and omnivores. However, in herbivores and humans the mouth opening to head size is quite small.
7. In carnivores and omnivores, the incisor teeth are short and pointed. In herbivores and humans, the incisor teeth are broad, flattened, and spade-shaped.
8. In carnivores and omnivores, the canine teeth are long, sharp, and curved. In herbivores, the canine teeth are dull and usually short, although sometimes they are long for defense. Other times, herbivores have no canines at all. In humans, they are short and blunted. It is worth pointing out that just because we refer to our own teeth as canines, does not mean they have anything in common with actual canines in carnivores and this name has more to do with their location on the jaw.
9. In carnivores and omnivores, their molar teeth are sharp, jagged, and blade-shaped. In herbivores, they are flattened with cusps or have a complex surface. In humans, they are flattened with nodular cusps.
10. Carnivores do not chew their food, they swallow it whole. Omnivores swallow food whole or perform simple crushing before swallowing. Herbivores and humans require extensive chewing before swallowing food.
11. The saliva in carnivores and omnivores contains no digestive enzymes whatsoever. The saliva in herbivores and humans contains carbohydrate digesting enzymes.
12. Carnivores and omnivores have what is called a “simple” stomach. Herbivores can have either simple stomachs or stomachs with multiple chambers. In this case, humans have simple stomachs. However, the pH of carnivore and omnivore stomachs is less than or equal to 1. In herbivores and humans, the stomach pH is between 4 and 5.
13. The stomach capacity of carnivores and omnivores is roughly 60% to 70% of the total volume of the digestive tract. In herbivores, it is less than 30% of the total volume of the digestive tract. In humans and frugivores, or animals that eat only fruit, it is 21% to 27% of the total volume of the digestive tract.
14. Carnivores have a liver that is proportionally 50% larger than others. Omnivores have a liver that is proportionally larger than herbivores. Herbivores have a liver that is proportionally larger than frugivores. Frugivores and humans have the smallest livers.
15. In carnivores and omnivores, the length of the small intestine is 3 to 6 times the body length, measured from neck to anus. In herbivores, the length of the small intestine can measure 10 to 12 times the body length, and sometimes more. In humans, the small intestines are 10 to 11 times the body length.
16. Carnivores and omnivores have colons that are simple, short, and smooth. Herbivores have colons that are long, complex, and may be sacculated. Humans have colons that are long and sacculated.
17. Carnivores and omnivores can detoxify preformed vitamin A from food with their liver. Herbivores and humans cannot and require pro-vitamin A carotenoids.
18. Carnivores and omnivores have kidneys that produce extremely concentrated urine. Herbivores and humans produce moderately concentrated urine.
19. Carnivores and omnivores have bile flow that is comparatively moderate to heavy. Herbivores and humans have bile flow that is comparatively weak.
20. The kidneys of carnivores and omnivores produce urate oxidase, or uricase. The kidneys of herbivores and humans do not.
21. The colons of carnivores and omnivores are alkaline. The colons of herbivores and humans are acidic.
22. For carnivores and omnivores, peristalsis does not require fiber to stimulate. For herbivores and humans, it does.
23. Carnivores and omnivores can metabolize large amounts of cholesterol efficiently. Herbivores and humans can only metabolize phytosterols efficiently.
24. Carnivores require approximately 2 to 4 hours to digest a meal. Omnivores require approximately 6 to 10 hours to digest a meal. Herbivores require approximately 24 to 48 hours to digest a meal. Frugivores and humans require approximately 12 to 18 hours to digest a meal.
25. Carnivores and omnivores cannot convert short chain fatty acids into long chain fatty acids. Herbivores and humans can.
26. Carnivores and omnivores have sharp claws. Herbivores have flattened nails or blunt hooves. Humans have flattened nails.
27. Carnivores and omnivores have zonary-shaped placentas. Herbivores and humans have discoid-shaped placentas.
28. Carnivores and omnivores cool themselves by panting and only have sweat glands in their paws if they have paws. Herbivores and humans have sweat glands all over their bodies.
29. Carnivores and omnivores are 100% covered in hair. Herbivores and humans have pores with extensive hair covering their bodies.
30. Carnivores and omnivores have multiple teats for nursing litters of offspring. Some herbivores also have multiple teats. Frugivores and humans have dual breasts for nursing one or two offspring.
31. Carnivores, omnivores, and herbivores walk on all fours. Humans and frugivores walk upright or at least have the ability to do so.
32. Carnivores, omnivores, and some herbivores produce vitamin C endogenously. Frugivores, some herbivores, and humans must consume vitamin C through their diet.
33. Carnivores require taurine in their diet which is found in most animal tissues such as muscle, viscera, and brain, but is not found in plants. Humans and most omnivores and herbivores synthesize taurine endogenously.
34. Carnivores and omnivores do not have prehensile arms, hands, feet, or tails. Herbivores and humans do.
35. The brains of carnivores and omnivores are fueled by fats and proteins. The brains of herbivores and humans are fueled by glycogen.
36. Carnivores and omnivores do not have full-color vision. Herbivores and humans have full-color vision.
37. Humans and herbivores sleep approximately 8 hours per 24 hour cycle, whereas carnivores and omnivores spend approximately 18 to 20 hours sleeping per 24 hour cycle.
38. Carnivores and omnivores drink by lapping their tongue. Herbivores and humans drink by sipping with their upper lip.
39. Carnivores are generally adapted for short sprints to catch their prey. Herbivores are generally adapted for endurance to outlast and outrun their predators. Humans are adapted for endurance (with these assistance of the aforementioned sweat glands).
40. Male carnivores do not have seminal vesicles as part of their reproductive anatomy. Male herbivores and male humans do have seminal vesicles. Erectile dysfunction is more often seen in men with elevated cholesterol levels and high levels of LDL “bad” cholesterol.
