What are humans originally supposed to eat?: Unpacking the Ancestral Diet

October 20, 2025 •

4 min read

For millions of years, human ancestors relied on a highly adaptable, omnivorous diet that shifted with geography and climate. This historical perspective directly addresses the question of what are humans originally supposed to eat?, revealing that there was no single "original" human diet but rather a flexible eating pattern of whole, unprocessed foods.

Quick Summary

Early human diets were not uniform, but varied mixtures of plants and animals, shaped by environmental availability and marked by the transformative advent of cooking. Evidence suggests a flexible omnivorous pattern prioritizing unprocessed, whole foods, rather than a single prescriptive diet.

Key Points

No Single 'Original' Diet: Early human diets were diverse and regional, consisting of a flexible mix of plants and animal products.
Cooking Transformed Our Diet: The control of fire and cooking increased nutrient absorption, shrank our guts, and fueled brain expansion.
Agriculture Introduced New Foods and Adaptations: The shift to farming brought grains and dairy, and human genetics adapted, exemplified by lactase persistence.
Ancestral Principles are Key: Emphasizing whole, unprocessed foods, lean protein, and healthy fats is more important than mimicking a specific ancient diet.
Modern Diets are a Mismatch: Many modern health issues are linked to the disparity between our evolutionary diet and today's heavily processed foods.
Flexibility is Our Legacy: Human evolution has favored adaptability; our most optimal diet is likely one that is diverse and nutrient-dense, not strictly restrictive.

The Evolutionary Roots of Human Nutrition

The concept of an ancestral diet is fascinating, but our understanding has evolved beyond the simplistic "caveman" image. The premise is that modern chronic diseases stem from a fundamental mismatch between our contemporary diet and the foods humans are biologically adapted to consume, based on millions of years of evolution as hunter-gatherers. Modern scientific techniques, including isotopic analysis of fossilized teeth and bones, dental microwear patterns, and even paleoproteomics and paleogenomics, are painting a much more complex picture of our ancestors' eating habits. This research reveals that dietary patterns were incredibly diverse and flexible, shaped by regional climates and available resources.

The Paleolithic Era: Beyond the "Caveman" Stereotype

The Paleolithic era, spanning from roughly 2.5 million to 10,000 years ago, is often cited as the period reflecting our "original" diet. However, there was no single Paleolithic diet. A group of hunter-gatherers in the Andean highlands 9,000 years ago, for example, primarily ate plants like tubers, with meat making up only a small fraction of their energy intake. In contrast, isotopic analysis of Neanderthal remains suggests they were apex carnivores in Europe. The diet of early hominoids likely began with frugivorous (fruit-eating) habits before evolving to include tougher plant materials, tubers, and seeds. A common thread was reliance on whole, natural foods, including:

Wild plants: fruits, berries, leaves, nuts, seeds, and starchy tubers.
Animal protein: meat from hunted animals, fish, shellfish, birds, eggs, and even insects.
Unprocessed fats: from nuts, seeds, and animal sources.

The Role of Cooking: A Culinary Revolution

One of the most significant events in human dietary evolution was the control of fire and the subsequent advent of cooking, which may have started as early as 1 to 2 million years ago. Cooking had profound effects on our biology and anatomy. By softening and breaking down food, cooking increased the energy yield from both meat and starchy plants, making digestion easier and more efficient. This increased energy availability is hypothesized to have fueled the expansion of the human brain, which is a metabolically expensive organ. The development of smaller teeth and jaws, as well as a smaller gut, also reflects our adaptation to a softer, cooked diet. Genes related to immune response and starch digestion were also impacted by the shift to cooked food.

The Agricultural Shift: A Double-Edged Sword

Roughly 10,000 years ago, the Agricultural Revolution marked a massive dietary change, introducing grains, legumes, and dairy as staples. This enabled settled societies and population growth but also led to a reduction in nutritional diversity and potentially poorer health outcomes compared to hunter-gatherers. However, human populations have also adapted genetically since this shift, with one notable example being lactase persistence, which allows adults in many populations to digest lactose in milk. This demonstrates that human evolution is ongoing and that we are not solely adapted to a single ancient diet.

Ancestral Principles vs. Modern Interpretations

Today's popular "Paleo diet" is an interpretation of this ancestral pattern, focusing on lean meats, fruits, vegetables, nuts, and seeds while excluding grains, legumes, and dairy. While a whole-food approach has merit, critics highlight that a true Paleolithic diet is impossible to replicate. The foods available today, even organic ones, are vastly different from their wild ancestors. Rather than strict replication, an evolutionary perspective on nutrition suggests focusing on key principles:

Prioritize whole, unprocessed foods.
Consume a wide variety of nutrient-dense plants and high-quality proteins.
Minimize processed sugars, refined grains, and industrial seed oils.
Cook and prepare foods to increase nutrient availability.

Ancestral Diets vs. Modern Western Diets: A Comparison


Feature	Ancestral Diet Principles	Modern Western Diet
Food Focus	Whole, unprocessed foods: diverse plants, lean wild game, fish, nuts, seeds	Processed foods, refined grains, added sugars, industrial seed oils
Carbohydrates	Variable, from wild fruits, tubers, and vegetables; low glycemic load	High, often from refined grains, starches, and sugary beverages; high glycemic load
Fats	Healthier profile from wild animals and nuts; higher omega-3s, lower omega-6s	Imbalanced ratio, high in omega-6s and often saturated and trans fats
Protein	Higher protein intake from lean, wild-caught sources	Often lower percentage of calories from protein, and often from factory-farmed animals
Fiber	Very high from plant matter; beneficial for gut health	Often low due to processed foods and lack of fruits and vegetables
Nutrient Density	High, naturally rich in vitamins, minerals, and phytochemicals	Lower, despite fortification; stripped of many natural nutrients
Processing Level	Minimal or none (e.g., cooking)	Extensive, including additives, preservatives, and artificial ingredients

Modern Nutrition Through an Evolutionary Lens

Applying these ancestral principles to our modern lives doesn't require hunting mammoth. It means prioritizing quality and minimizing ultra-processed foods that our bodies are not equipped to handle in large quantities. Focus on filling your plate with a variety of colorful vegetables, seasonal fruits, and lean protein sources. Good fats from avocados, nuts, and quality oils are also beneficial. While the exclusion of entire food groups like grains and legumes is debatable and not universally supported by science, emphasizing whole-food sources over refined ones aligns well with our evolutionary history.

Conclusion: Embracing Nutritional Flexibility

So, what are humans originally supposed to eat? The answer is not a single, prescriptive list but a dynamic, omnivorous diet built on flexibility and whole foods. Our ancestors were opportunistic eaters, and this adaptability is encoded in our genes. By understanding our evolutionary dietary journey—from early plant-eaters to opportunistic carnivores and cooked-food consumers—we can make more informed choices today. Rather than obsessing over a strict "Paleo" blueprint, we can take lessons from our past: prioritize whole, minimally processed foods, embrace cooking, and listen to our bodies. The goal is a dietary pattern that supports long-term health and reduces our reliance on the processed foods that contribute to modern health problems.

Frequently Asked Questions

While the consumption of meat and marrow was a significant evolutionary shift for early hominins, the amount varied greatly by region and time period. Some groups ate a substantial amount, while recent studies show other hunter-gatherer communities relied heavily on plants.

The carbohydrate content of Paleolithic diets varied. Hunter-gatherers relied on wild fruits and starchy tubers, which were often cooked to increase their digestibility, indicating a varied intake, not necessarily low-carb.

Cooking made food easier to chew and digest, increasing the net energy gain from both meat and plants. This allowed for a smaller gut, fueling the development of our larger brain and significantly altering our dietary capabilities.

Grains and legumes were introduced with agriculture, and some modern humans have adapted to digest them. While many modern diets rely heavily on refined versions, whole grains and legumes are considered healthy sources of fiber and nutrients by most major health organizations.

No, modern fruits and vegetables have been cultivated and selectively bred over centuries, making them much different from their wild ancestors in terms of size, sweetness, and nutritional content. A true replication of the ancient diet is impossible.

The health benefits some people report are likely due to the emphasis on whole, unprocessed foods and the avoidance of added sugars and unhealthy fats, rather than the elimination of entire food groups like grains and legumes.

Yes, human gut morphology has adapted to a higher-quality, more digestible diet compared to other primates. However, the human gut microbiome is complex and influenced by a variety of factors, and maintaining a healthy gut today requires a varied, fiber-rich diet.