Home / C. Nature, biology and evolution / Part DIR
"We have canine teeth; we are omnivores."
being able to eat meat doesn't mean needing to eat it, let alone being obliged to. Humans are omnivores: we can digest both plants and animals. It's exactly that flexibility that makes it possible to live well on plants alone. Anatomy says what we can do, not what is right to do.
Short answer
We're omnivores, and that's exactly why we can choose: we can live well on plants or on animals. Being able to eat meat isn't needing to, and needing to isn't being obliged to. Our canines are small compared with a carnivore's and are also used for biting fruit and vegetables. And anatomy gives no moral orders: we're also capable of many things we choose not to do.
For children
Your teeth are for biting lots of things: apples, carrots, bread, nuts. Having strong teeth doesn't mean you have to bite everything you can. We can also climb trees, and that doesn't mean we have to live in them. The body shows what we're able to do, and we choose what's good to do.
"If we're omnivores, doesn't that mean we can also live on plants alone?"
Como pode aparecer
"Look at my teeth."
"We have canines."
"Our gut is an omnivore gut."
"If we were meant to be herbivores, we'd have four stomachs."
"What are canines for, then?"
"Humans are biologically omnivorous."
"My body craves meat." (which is C11)
The strongest version
"Look at my teeth. We have canines; we're omnivores. We were made to eat meat."
Strongest version (steelman):
- P1Human anatomy and physiology make it possible to digest and use animal foods.
- P2These traits evolved because our ancestors ate meat.
- P3What the body is adapted to is legitimate.
- CSo eating meat is legitimate for humans.
P1 and P2 are true. The problem lies in P3, which moves from describing the body to a rule of conduct.
The argument is valid. Its soundness fails at P3: it's an appeal to nature (C1) and a move from "is" to "ought".
Full answer
- a
Reconstruction and diagnosis
The argument runs three different claims together as if they were one:
Claim True? We can digest meat Yes We need to eat meat No, for anyone with access to a varied diet We ought to eat meat It doesn't follow from either of the above - b
Where the argument breaks
1. Omnivore means flexible.
Being an omnivore means being able to get nutrients from varied sources. That includes the possibility of getting them from plants alone, as the US Academy of Nutrition and Dietetics recognizes in considering well-planned vegan diets adequate.
2. Can isn't ought.
The human body is capable of many things we choose not to do. Anatomy describes abilities, not obligations. It's the move from "is" to "ought" (C1).
3. Human canines aren't a carnivore's.
Human canines are small and used for biting a variety of foods. Other primates with large canines, like gorillas, eat a mostly plant-based diet.
4. We eat meat cooked and processed.
Most of the meat we eat goes through fire, knives, seasoning and industry. The anatomical argument talks about the body but describes a practice that depends on technology, not on anatomy.
5. The argument ignores today's context.
The question isn't what our ancestors could eat, but what we, with supermarkets and alternatives, ought to eat.
- c
Data and sources
Source What it says Note Academy of Nutrition and Dietetics, 2016 Well-planned vegan diets are healthful and appropriate at all stages of life, with a reliable source of B12 Official position Gorillas: teeth and diet Gorillas have large canines and a mostly plant-based diet Summary of the primatological literature, with sources - d
The strongest counter-reply: adaptation points to the ideal diet
The most serious version says anatomy indicates the diet the body is best adapted to, and that ignoring it can carry health risks. A diet without meat would need supplements, like B12, precisely because it isn't the "natural" diet.
- e
Why the counter-reply doesn't reach the conclusion
It changes the subject.
It becomes a health argument (family G), and the evidence shows well-planned vegan diets are adequate.
Supplementing doesn't invalidate it.
Farmed animals also get supplemented B12 in their feed, and we use supplements and fortified foods in many other situations (G3).
Adaptation explains; it doesn't oblige.
Even if meat were ideal for the body, that wouldn't say whether it's just to get it at the cost of others' lives.
Reasoning errors
Logical
Is the form valid?
Hume's law (from is to ought)
Equivocation
Epistemological
Does the evidence support it?
Misread anatomy
Moral
Is the criterion coherent?
Appeal to nature
Biases
Illusory truth effect
The line about canines is repeated without anyone looking at gorillas
Extrapolations
The principle being tested is: "what the body can do is legitimate".
If it applied to…Physical violenceTap to see
It would be legitimate, because the body can do it
No one accepts this
If it applied to…Eating human fleshTap to see
It would be legitimate, because the body can digest it
No one accepts this
If it applied to…Plant-based dietsTap to see
They'd also be legitimate, because the body can manage them
The argument doesn't exclude a vegan diet
Contradictions
We can do many things we don't do.
The human body depends on fire and cooking to eat meat safely.
No one thinks an omnivore is obliged to eat everything.
What the argument gets right
What is true
The description is correct: humans are omnivores, can digest meat, and our anatomy carries the history of a varied diet. It's also true that nutrition matters and that a diet without meat takes some planning.
But
But anatomy says what we can do, not what we should. And, ironically, being an omnivore is exactly what makes it possible to choose to live on plants alone.
Connections
Usually comes before
Usually comes after