In this article we’re tackling a big question that stirs up a lot of debate: Are humans built more like carnivores or herbivores? We’re going to compare gut to body length ratio, stomach acidity, digestive enzymes, and the actual structure of the GI tract to see which side humans really lean toward. Spoiler: the answer is a lot more interesting than you think.
Let’s start with gut length—one of the most common arguments in this debate. Herbivores like cows and gorillas have very long digestive tracts, often 10 to 12 times their body length to accommodate the relatively slow fermentation process.
Carnivores, on the other hand, have short guts—typically 3 to 6 times their body length—so meat can move through quickly before it putrefies. Humans overlap carnivores with a gut around 5 to 7 times our body length- placing us much closer on the spectrum to carnivores than herbivores. But there’s more to the story than just gut to body length ratio.
Next, let’s look at stomach acid. Note that pH is exponential so 2 pH is 10 times more acidic than 3 pH. True carnivores have very acidic stomachs, usually around 1 to 2 pH, strong enough to break down raw meat and kill pathogens. Herbivores generally have much weaker acidity—around 4 to 7 pH—because they rely on fermentation. Humans? We have a fasting stomach pH of about 1.5, which is right in the carnivore range.
This brings us to the actual digestive processes each species depends on. Carnivores digest food primarily through acid proteinase enzymes like pepsin that break down muscle tissue. Herbivores rely on slower microbial fermentation, using gut bacteria to break down cellulose. Humans digest the majority of our nutrients through acid digestion, not fermentation. We do have some fermentation capability in the large intestine, but it’s tiny compared to herbivores.
Anatomy tells the same story. Carnivores have a single-chamber stomach, a small cecum, and a short colon. Herbivores usually have either a multi-chambered stomach—like cows and sheep—or an enormous fermentation colon like gorillas and horses. They also have a large, functional cecum to ferment plant fibers. Humans have a single stomach, not multiple chambers. Our cecum is small, and vestigial. And our colon is proportionally much smaller than that of herbivores.
So where do humans land? Based on gut length, stomach acidity, digestive enzymes, and the physical structure of our GI tract, humans lean anatomically much closer to omnivores with strong carnivorous traits than to herbivores.
That doesn’t mean you have to eat only meat—but it does mean our biology is clearly adapted to digest and thrive on animal foods.
If you found this breakdown thought provoking, please leave your thoughts in the comments section below. Thanks for your interest!
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