This piece is part of my “Arguments” series. In this collection of posts, I examine and respond to some of the most common arguments used to defend the exploitation of animals or to criticise veganism.
These articles are not intended to be exhaustive treatments of each topic. Rather, they are designed as practical reference pieces, helping readers reflect on these arguments more carefully and respond to them in a thoughtful, informed way.
You can find other entries in this series here.
The Claim
It is often argued that eating animals is morally acceptable because it is “natural.”
Humans, after all, have evolved to be able to digest meat. We have teeth that can tear it, a digestive system that can process it, and our ancestors often hunted animals. From this, some people conclude that eating animals is simply part of human nature.
To a limited extent, this is true. Humans are biologically capable of eating animal products, and many societies have done so throughout history (1). This is not debatable.
However, this observation alone tells us very little about what we ought to do today.
The Short Answer
Humans are capable of eating animal products, but being capable of something does not make it ethically justified.
Major health organisations agree that people can be healthy on well-planned plant-based diets. This means that, for most people today, eating animals is a choice, not a necessity.
Appealing to what is “natural” is a recognised logical fallacy. Many harmful things are natural, and many beneficial things are not. Biology alone does not tell us how we ought to behave. Modern animal agriculture is an industrial system with serious ethical and environmental consequences; it is not simply an expression of human nature.
If alternatives exist (and they do), then tradition and biology are therefore no longer enough to justify continuing a harmful practice.
The Detail
Biological Ability Is Not Moral Guidance
An extensive body of research shows that humans can thrive on well-planned plant-based diets. Major dietetic organisations have concluded that appropriately planned vegetarian and vegan diets are nutritionally adequate for all stages of life (2)(3), and global public health bodies recognise the role of plant-based dietary patterns in reducing chronic disease risk (4).
This means that, for most people in industrialised societies, eating animals is not a biological necessity. It is a choice. Once something is a choice rather than a requirement for survival, it becomes open to ethical evaluation. We cannot justify it simply by pointing to biology – being able to do something does not mean that we should do it.
Humans are capable of aggression, territorial violence, and domination of weaker groups. These behaviours may once have had evolutionary advantages (1). Yet we no longer regard them as morally acceptable. Moral progress often involves moving beyond the behaviours and practices that once came natural to us.
The Appeal to Nature Fallacy
Philosophers and logicians describe this type of reasoning as an “appeal to nature,” or a form of the naturalistic fallacy: The idea that something is good or right simply because it is natural, and the related claim that something is bad or wrong simply because it is unnatural (5)(6).
This is a well-established logical error. Many things that are natural are harmful, and many things that are beneficial are artificial.
Disease, famine, and violence are natural phenomena. Vaccines, sanitation systems, surgery, and wearing glasses are not. Few people would argue that we should abandon antibiotics because they are “unnatural,” or accept suffering because it is natural.
Is it wrong to be reading this on your phone or computer screen, on the basis that doing so is not natural? If your arnswer is no, then you already recognise that “natural” is not a reliable guide to ethical behaviour.
Selective appeals to nature usually reflect convenience rather than principle.
Modern Meat Consumption Is Not “Natural”
Even if we accept that some form of meat consumption occurred in human history, this bears little resemblance to how most animal products are produced today. We are not discussing small-scale subsistence hunting for survival, we are discussing.
- Industrial breeding
- Intensive confinement systems
- Routine use of antibiotics and pharmaceuticals
- Mechanised slaughter
- Globalised supply chains
Billions of animals are raised and killed annually in highly controlled, technologically complex systems (7).
This production model has profound environmental consequences. Research published in Science demonstrates that animal agriculture is one of the most significant contributors to land use, biodiversity loss, and greenhouse gas emissions globally (8).
Whatever we think of prehistoric diets, or the meat-based diets of indigenous culures in today, modern industrial animal agriculture is not a simple continuation of “nature.” It is a large-scale technological enterprise. Calling it “natural” obscures the reality of how it actually functions.
Ethics Requires Reflection, Not Habit
The underlying problem with the “natural” argument is that it replaces moral reasoning with habit. It suggests that because humans have done something in the past, because it is part of our natural history, it does not need to be questioned.
Yet many practices that were once widespread and culturally embedded have since been reconsidered after moral reflection. Progress has often required people to ask not what is customary, but what is justified. When alternatives exist, continuing a harmful practice requires stronger justification than tradition or biology alone can provide.
Summary
Humans are biologically capable of eating animal products, but this does not make doing so ethically justified. Major health authorities confirm that well-planned plant-based diets are nutritionally adequate (2)(3). In most modern societies, consuming animal products is a choice rather than a necessity.
Appealing to what is “natural” in defence of ethical choices commits a recognised logical error (5)(6). Natural behaviours are not automatically good, and unnatural practices are not automatically bad.
Modern animal agriculture is an industrial system with significant ethical and environmental consequences (7)(8), not a simple expression of human biology.
Ethical questions require reflection, not habit. If alternatives exist, the mere fact that something once came naturally is not, by itself, a moral defence.
Bibliography
- Lieberman, D. E. (2013). The Story of the Human Body: Evolution, Health, and Disease. Pantheon Books.
- Academy of Nutrition and Dietetics. (2016). Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1970–1980. https://doi.org/10.1016/j.jand.2016.09.025
- British Dietetic Association. (2017).
https://www.bda.uk.com/resource/vegetarian-vegan-plant-based-diet.html - World Health Organization. (2015). Healthy Diet Fact Sheet.
https://www.who.int/news-room/fact-sheets/detail/healthy-diet - Moore, B., & Parker, R. (2017). Critical Thinking (12th ed.). McGraw-Hill Education.
- Stanford Encyclopedia of Philosophy. (2021). Naturalistic Fallacy.
https://plato.stanford.edu/entries/naturalistic-fallacy/ - Food and Agriculture Organization of the United Nations. (2018). Livestock’s Long Shadow. http://www.fao.org/3/a0701e/a0701e.pdf
- Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987–992.
https://science.sciencemag.org/content/360/6392/987
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