Can Humans Be Carnivores? A Biological Analysis

The term “carnivore” biologically defines an animal that feeds on the flesh of other animals. Humans are broadly classified as omnivores, consuming a mix of plant and animal matter. However, the increasing popularity of diets consisting exclusively of meat has sparked a debate about whether humans can sustain themselves as carnivores.

Human Physiological Traits for Meat Consumption

The human body possesses several features that accommodate the consumption of meat, though they differ from those of obligate carnivores like cats. Human teeth, for instance, represent a versatile toolkit. Incisors are suited for biting and canines for tearing, while flatter molars are efficient at grinding, a combination that points to an omnivorous diet rather than the specialized shearing dentition of a pure carnivore.

Our digestive system also shows adaptations for meat. The human stomach maintains a highly acidic environment, comparable to that of scavengers. This high acidity aids in breaking down complex proteins found in meat and helps to neutralize harmful pathogens. Compared to herbivores, the human digestive tract is significantly shorter, a trait shared with other meat-eaters, reflecting less need to ferment fibrous plant matter.

The structure of human fat cells, which are numerous and small, also aligns more closely with carnivores than with omnivores or herbivores, who tend to have fewer, larger fat cells. While these traits confirm humans are well-equipped to process meat, they exist alongside features suited for plant consumption, painting a complex picture of our dietary adaptability.

Nutritional Sufficiency on an All-Meat Diet

An all-meat diet can supply a wealth of certain nutrients. Animal products are complete sources of protein and provide fats that are a dense source of energy. Micronutrients like vitamin B12, highly bioavailable iron, and zinc are abundant in meat, and obtaining them from plant sources can be more challenging.

However, concerns arise regarding nutrients associated with plants. Vitamin C, for example, is not found in significant amounts in cooked muscle meats. To obtain sufficient vitamin C, a person on a carnivore diet would need to consume fresh or lightly cooked meats and specific organ meats. Similarly, folate can be deficient if the diet is not varied enough, though beef or chicken liver are rich sources.

The complete absence of dietary fiber is another significant aspect of an all-meat diet. Fiber supports digestive health by feeding gut bacteria and promoting regular bowel movements. While proponents of carnivore diets suggest that fiber is unnecessary, its absence leads to a different gut microbiome composition, and its long-term effects are not fully understood. Electrolytes like potassium and magnesium, also more commonly found in plant foods, must be carefully considered to avoid deficiencies.

Observed Health Impacts and Scientific Perspectives

Proponents of the carnivore diet report a range of benefits. Anecdotal accounts include significant weight loss, improved mental clarity, and relief from autoimmune conditions and inflammation. Some studies on low-carbohydrate diets, which share similarities with the carnivore diet, have shown improvements in markers related to metabolic health, such as insulin sensitivity and triglyceride levels.

Despite these claims, the scientific and medical communities raise several concerns about the long-term health implications of an exclusively meat-based diet. A major point of discussion is the high intake of saturated fat and its potential impact on cardiovascular health by raising LDL cholesterol levels. The lack of fiber can negatively affect the gut microbiome, and there are risks of nutrient deficiencies if the diet is not carefully constructed.

There is a significant lack of long-term, large-scale scientific studies specifically examining the carnivore diet in humans. Much of the current understanding is based on short-term studies, anecdotal reports, or research on similar low-carbohydrate diets. Therefore, while some individuals report positive experiences, the broader scientific consensus remains cautious about the potential long-term risks of such a restrictive eating pattern.

Evolutionary Context of Human Meat Consumption

Archaeological evidence, such as stone tools for butchering and cut marks on ancient animal bones, indicates that meat has been a component of the human diet for millions of years. The incorporation of animal foods into the diet of our ancestors, such as Homo erectus, is often linked to evolutionary changes, including the development of larger brains, which require a dense source of energy and nutrients.

This dietary shift was a departure from the diets of earlier primates and is believed to have been a driving force in human evolution, providing the calories to support a larger brain. The “expensive tissue hypothesis,” for example, suggests that as the human brain grew, the energy-demanding digestive tract became smaller, a change made possible by a higher-quality, more easily digestible diet that included meat.

While meat was an important part of our ancestral diet, the evidence does not support the idea that early humans were exclusively carnivores. Most findings suggest they were adaptable, opportunistic omnivores who consumed a wide variety of foods based on their environment and resource availability. Recent analyses also suggest that the explosion of archaeological evidence for meat-eating around 2 million years ago may be partly due to more intensive research focused on that period, complicating the narrative that “meat made us human.”