“Humans Are Omnivores with Canine Teeth and Front-Facing Eyes.”

The case for veganism has nothing to do with this issue. Simply put, the case for veganism is that it’s ethically wrong to cause unnecessary harm to animals. Because it’s not necessary to eat animal products for nutrition, any claims that we are natural omnivores are rendered meaningless in this context.

As we discussed earlier, the argument for veganism does not depend on humans having any specific physical traits. Canine teeth are discussed here only because it is a frequently voiced objection to veganism.

Hippopotamuses,¹ gorillas,² camels,³ and saber-toothed⁴ deer all have sizable canines, and all are herbivorous. Herbivores use canine teeth in various ways. Sizable canines in herbivores are often for defense.

The relatively short, blunted canines in humans can assist in biting into hard, crunchy plants (such as apples) and ripping vegetable matter, preparing the food for grinding by the other teeth.

One thing seems obvious—human canines are not adequate to kill prey or tear raw flesh for eating.

According to Dr. Milton Mills in his paper, “The Comparative Anatomy of Eating,” we more closely match herbivores in nineteen traits, as summarized below.

Note: Whether this adequately demonstrates that humans are herbivores is open to dispute, and we are not making that claim here.

From Dr. Milton Mills
Comparative Anatomy of Eating⁵

Dr. Colin Barras, a paleontologist and science writer, believes that “archaeologists tend to emphasize the role of meat in ancient human diets, largely because the butchered bones of wild animals are so likely to be preserved at dig sites. Edible plants may have been overlooked simply because their remains don’t survive so well.”⁶

Rob Dunn declares in Scientific American that “human ancestors were nearly all vegetarians.” In making that assertion, and in questioning the validity of paleo claims, he deems it important to look at the diets of our ancestors at the time our guts were evolving. He states that for primates, a group to which humans belong, plants “were our paleo diet for most of the last thirty million years during which our bodies, and our guts in particular, were evolving. In other words, there is very little evidence that our guts are terribly special and the job of a generalist primate gut is primarily to eat pieces of plants.”⁷

The concept of a natural diet might make some sense in the context of gatherers and hunters. But since the invention of agriculture, with its selective breeding of both plant and animal species, the label loses its meaning.

Also, to make the claim that humans are natural omnivores, one needs to define what is meant by “natural” in this context. If by “natural” you are referring to the ability to obtain nutrients, then humans are omnivores, as we can digest both plants and meat. But, as shown earlier, that still cannot negate the case for veganism.

If you mean it’s natural because it’s nutritionally the best diet for humans, then you are on shaky ground. There’s an increasingly large body of research, as mentioned and cited above, supporting the contention that the closer we are to a varied herbivorous diet, the greater our general health and the lower our risk for a multitude of chronic diseases.

Finally, the claim that humans are natural omnivores can be thought of as an example of the naturalistic fallacy. That is to say, being natural doesn’t make something ethically or nutritionally sound.

Carnivores have the athletic prowess and anatomical features necessary to not only catch and kill their prey but also to tear and rip apart the carcass and process it for eating. Humans lack these features and must use sophisticated tools, such as spears and knives, to accomplish these tasks.

The claim is made that since many prey animals have eyes on the side of the head and many predator animals have eyes on the front of the head, it follows that humans, who have eyes on the front of the head, are designed to eat copious amounts of meat. The point is made moot, however, not only by the fact that the argument for veganism does not depend on physical traits but also by the fact that our closest relatives in the animal kingdom, the primates, have eyes in the front of the head.

At least three advantages of frontal eyes for primates have been proposed.

• Binocular vision is crucial for the manipulation of plant foods. A study titled “Binocularity and brain evolution in primates,” published by the National Academy of Sciences, concludes that “fine-grained stereopsis [binocular vision] is likely to be critical for the visually guided, delicate manipulation of plant foods.”¹⁹
• The ability to “see through” foliage is advantageous. The ability to “see through” foliage is advantageous. Theoretical neurobiologist Mark Changizi and Professor of Experimental Psychology Shinsuke Shimojo propose in the Journal of Theoretical Biology the “X-ray vision” hypothesis. According to Changizi and Shimojo, front-facing eyes gave our ancestors the advantage of being able to “see through” the cluttered foliage in the forest. You can see this effect, he states, by placing a finger in front of your eyes and noting that the finger does not block the view of anything behind it.²⁰
• Arboreal locomotion requires accurate depth and distance perception. The depth and distance perception afforded by front-facing eyes was useful to our ancestors in jumping from branch to branch and tree to tree. This idea was proposed in 1922 by Edward Collins and has subsequently been expanded and refined.²¹