Saturday, 12 November 2011

“We have canines, we’re meant to eat meat!”

Having been vegetarian for six years and read a considerable amount of relevant discussion online during this time, I’ve noticed that those who attempt to defend the killing or exploitation of animals for food typically do so with highly simplistic arguments. One such argument is that human beings possess canine teeth and are therefore meant to eat meat. Stated in this form, this is of course not a valid logically deductive argument, for the conclusion does not follow necessarily from the premise. Further premises are clearly required in order for this argument to be logically valid:

  1. Human beings possess canine teeth.
  2. Mammals which possess canine teeth are meant to eat meat (or All mammals with canine teeth eat meat).
  3. Human beings are mammals.
  4. Therefore, human beings are meant to eat meat.
Formulated in this way, the conclusion necessarily follows from the premises. The problem with this argument, however, is that the second premise is false. There are a number of examples from nature that show this statement to be false and therefore provide a powerful defeater for the argument.

One such example is the Western lowland gorilla. The natural diet of the Western lowland gorilla consists almost entirely of fruits, leaves, and other plant matter. Popovich et al (1997) found them to consume over 200 species and varieties of plants and 100 species and varieties of fruit. Importantly, there is a “virtual absence of foods of animal origin” in their diet (Popovich et al, 1997). It is surprising, therefore – on the view that possessing canine teeth entails eating animal flesh – that the Western lowland gorilla not only has canine teeth, but has canine teeth which are considerably larger than the rather small and feeble human examples.

This absence of foods of animal origin is something that the Western lowland gorilla shares in common with all other great apes apart from the chimpanzee, which occasionally hunt and consume small vertebrates (Popovich et al, 1997). The large canine teeth of Western lowland gorillas are also characteristic of other primates. Plavcan and Ruff (2004) were able to demonstrate that “relative to skull length and body mass, primate male canines are on average as large as or larger than those of similar sized carnivores”, that “the range of primate female canine sizes embraces that of carnivores” and that “male and female primate canines are generally as strong as or stronger than those of carnivores”.

In short, the fact that the Western lowland gorilla has considerably larger canine teeth than humans and eats a diet devoid of foods of animal origin provides a straightforward refutation of the idea that having canine teeth means that humans are “meant” to kill and eat animals. Even if such a straightforward refutation did not exist, there are other powerful objections to deriving behavioural obligations from such basic anatomical facts. I discussed these objections in more detail in a previous post, but suffice it to say that while evolution has given us canine teeth barely worthy of the name, it has also endowed us with the capability for moral thought, higher-order cognitive faculties, and a tremendous amount of behavioural plasticity. Moreover, it has seemingly provided us with a physiological makeup which allows for a diet not containing food of animal origin to be at least as healthy, but probably healthier, than one containing such foods. 


  1. Excellent points! Especially about our very insignificant "canines" - Certainly inferior for taking down prey or ripping flesh from their bodies...

    It is for this reason that I refrain from calling them canines and prefer instead to name them as most in the medical field do: cuspids. It's my understanding that canines refer to nonhuman animals and cuspids belong to man.

    In any case - Canines or not... We certainly should as the thinking (ethical) species attempt to evolve beyond our dentures.

    Thanks for your thoughtful blog... Have subscribed and looking forward to reading more of your posts.

  2. While you're right in destroying this argument, the argument you've presented is a strawman. Being charitable is an important part of having a well-informed discourse. It's a nice blog, though, when this sort of thing isn't happening. Cheers.

  3. If I've 'presented a strawman', feel free to articulate the actual argument for human dentition indicating that meat is a requisite part of our diet.