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I am a politically-progressive, ethically-herbivorous anthropoid pursuing a paleontology education in the Los Angeles Basin. I am largely nocturnal, have rarely been photographed, and cannot thrive in captivity.

12 July 2010

Deer Fangs & Deep Time: The History Of Your Teeth, Part I


You're not seeing things, and it hasn't been photoshopped. That really is a picture of a deer with fangs. It's a musk deer, and a photo of its skull gives you an even more ominous view of its frightening dentition:
Musk deer aren't considered "true" deer, however. They belong to the family Moschidae, and true deer to the family Cervidae.

But that doesn't let us out of this strange world of fanged deers. For among the Cervidae, there are three species of deer with fangs; the muntjac, the tufted deer and the Chinese water deer. And as many hunters can attest, sometimes even white-tailed deer sport a set of nasty canines.

So, what is going on here, and what the heck does it have to do with veganism? Well, if you're like me, you've been confronted with the argument that "humans have canines, therefore we must be meat-eaters"; or, more broadly, that "humans have meat-eating teeth." Our teeth are used as a defense of human carnivory, yet another piece of evidence that our critics insist means we must eat meat. It's part of our evolution, after all. Teeth don't lie.

What, I wonder, would such critics make of this argument if confronted by a fanged deer? Would they imagine that these deer eat meat? Or would they recognize that deer fangs are a primitive characteristic put to a new use, inherited from the deer's distant ancestors, many of whom were not highly-specialized herbivores? And if they can acknowledge this about deer, why can't they do the same for humans?

It's true that humans have canines, and teeth that are generally described as "omnivorous." Like other primates, we are equipped with a set of primitive characteristics that make us successful dietary generalists. But as I've noted before, that is only the beginning of a discussion, not the end of one. It tells us something about our capabilities, but nothing about our obligations, particularly to nonhuman animals.

Why, then, the big deal about teeth? Vegans and carnists both argue about them incessantly, apparently convinced that teeth are the key to proving our "ideal" (and therefore, it's often implied, our obligatory) diet. I used to do the same, insisting that because we don't have specialized carnivore teeth, we must therefore be natural herbivores. But since I started studying evolution and paleontology, I've come to understand that both "sides" are right. Or perhaps, that neither of them is. Human teeth are generalist, specialized neither for herbivory (like deer) nor for carnivory (like lions).

In short, they're not nearly as profound to either sides' ethics as they both like to think. I no longer argue that our teeth prove we aren't meat-eaters by nature. I now simply point out that our teeth really aren't useful in figuring out what our "ideal" diet should be. Vegans and carnists both make the same mistake in marshaling tooth evidence for their side.

To help put this debate point in its proper context, I'll spend the next few posts discussing the history of human teeth, going all the way back to our pre-mammalian ancestors in the Permian, before dinosaurs walked the earth. It's a history few people know, and one that I have come to find eminently fascinating.

To start, we should understand that teeth are one of the defnining characteristics of mammals. Mammals are heterodonts, meaning that we have teeth of many different shapes. Other kinds of animals aren't like this; reptiles and fish, for instance, have teeth of different sizes in each individual, but all of them are basically the same shape. The University of Michigan's Animal Diversity Web has an excellent primer on mammalian teeth, and I won't reproduce its work here. Instead, I'll focus on how mammal teeth got to be this way, and show that human teeth are just a variation on the generalist pattern most mammals possess. And thus, that they can't really be used to define the ethical debate over veganism, one way or the other.

6 comments:

  1. I love that you're discussing this.

    It should also be pointed out that long, large canines in herbivorous animals are often believed to be present for defensive/intimidation purposes. More closely related to us than deer, gorillas too have very prominent canines and eat an almost exclusively vegetarian diet. So yes, canines in some animals (along with other characteristics) indicate carnivory, while in others they can serve the very different function of warding off predators or asserting dominance.

    To add to the conversation, I think differences in gut morphology almost tell us more about what an animal's optimal diet "should" consist of. Humans do not have the short digestive system of a "carnivore", nor do we have the multi-stomach setup of many "herbivores." But just because we're not specialized in one direction, it does not mean we MUST eat everything.

    So I agree with you that human dentition (and even gut design) does not necessitate an omnivorous diet--it allows for one, but we're in an interesting position of being aware of and having many choices. The most recent science and most of the major health organizations would actually lean away from veggie naysayers, concurring that a more heavily plant-based diet is optimal for human health. While we CAN digest meat, eating it in excess can lead to serious digestive and bowel complications--a much more compelling argument than those canines, I feel.

    I'm not vegan myself, but I very much enjoy the fact that you're speaking to this issue from this angle. The moral, social, economical, and environmental aspects are all important, but we often disregard or incorrectly invoke the evolutionary points. I'm looking forward to your future posts on this.

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  2. Thanks, Britt! :)

    You're spot-on in most of your observations. I'm actually planning, long-term, to do a series about gut morphology, too. But that will be a bit more speculative than this one, since soft parts rarely fossilize.

    Your point about the usage of canines by different mammal species hints at one of the big misconceptions about evolution: that everything is an adaptation to a given species circumstances. In fact, this isn't true at all. Most traits are adaptations to your deep ancestors' conditions, not your own.

    In other words, canines don't exist either for carnivory or defense, specifically. We have them because our distant ancestors did. We may put them to many primary uses depending on our species, but that doesn't mean they evolved FOR those uses.

    Please keep reading, as I will be going into further detail about mammal evolution and the story of your teeth. I hope you will both learn from and enjoy it.

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  3. I am totally with you on that. I think there is a misconception that certain traits evolved FOR a specific purpose. Every trait that we possess has endured because it occurred in one of our ancestors, was advantageous, and selected for, not because Nature waved a magical wand and said, "You get canines for eating meat!" What I was rather saying is that it is believed that long canines have remained present, or been selected for, in certain modern, primarily herbivorous mammals because they offer a defensive/social advantage. It can be assumed that large canines phased out in humans because things like bipedalism and larger brains were more advantageous in this department.

    Of course this is all gross over-simplification, but it's a bit hard to avoid when speaking with any sort of brevity about such a complex issue. I was a minor in Anthropology at NYU with a focus on evolution and primate ecology, so I have a great appreciation for what you're speaking to here and the effort that you're making to ensure that people have a clear comprehension of evolutionary biology. Few things are so tragically misunderstood as our own evolutionary history!

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  4. http://www.care2.com/greenliving/good-nutrition-for-healthy-vegan-dogs.html don't forget the lies that dogs need meat!

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  5. While I accept the interesting nature of these (vestigial) teeth, I wonder if their use is in defence or mate selection and not in diet (like the Narwhal "tusk" (elongated canine tooth). By having the matching lower canine tooth, humans and other omnivores (ie bears, raccoons) have the grasping ability that is one of the main purposes of the canines. The deer skull shown is interesting but as it is a vegetarian, it lacks the lower canine because its prey doesn't run away and need to be grasped.

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  6. Humane Hominid, I noticed that you follow Scott Sampson's blog. I enjoyed his insightful essay on The Whirlpool of Life.

    My seven-year old daughter is a big fan of Dinosaur Train on PBS. I happened to catch the end of the episode on Troodons and noticed Dr. Scott explain how Troodons were omnivores like us humans who "eat fish, chicken and beef" (http://www.youtube.com/watch?v=ZqYZtzSfEi0). I don't disagree that we are omnivores but to categorize human omnivorism by what modern humans eat didn't quite sit right with me. So I wrote to him and asked him whether fossil evidence alone could in fact reveal what manner of omnivore humans are or should be. His response seemed to say that teeth are definitive indicators of our diet:

    "Teeth are perhaps the single best indicator of diet, and it's remarkable how similar the teeth of pigs and humans are. (Paleontologists often confuse them when found as isolated fossils in the field.) Pigs are one of the best examples of omnivores, and our teeth too reveal a lengthy history of mixed diet that included both plants and meat (including fish, fowl, and mammal). So eating plants and meat is wholly "natural" for our species, and an alien visiting Earth might well conclude based only on bony and dental evidence that humans fall within this mixed-feeder category known as omnivores."

    Anyway, I wrote back to him and asked him what the alien visitor might make of the fossilized skulls of other primates such as gorillas, organutans, or chimpanzees - all who are primarily vegetarian - and for some of them (gorillas and orangutans) the only "meat" that they eat is insects. Would the alien visitor conclude that they are meat eating omnivores or would the alien visitor be able to tell that the gorillas and orangutans were almost exclusively vegan with the exception of some insects? He did write back but did not offer any thoughts on my question/observation.

    In my opinion even the most brilliant and thoughtful among us (humans) quite often let the culture of meat eating colour our professional insights. I'd appreciate any insights from you.

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