Stone Age Sustenance: How Meat and Animal Fat Shaped Paleolithic Diets

The short answer is no, 'the human diet’ as such does not exist. Human diets have evolved across a wide spectrum of regional, seasonal, and ecological contexts. Early hominins were opportunistic foragers, relying on both plant and animal resources for survival. However, as they transitioned from forests to open savannahs, the dietary role of red meat, marrow, and organ meats became increasingly important. Moreover, these foods provided an abundance of energy, fat, protein, and micronutrients that were crucial for brain expansion and led to a range of anatomical and metabolic adaptations, causing humans to diverge from other apes. It is likely that even young children, including older infants, became dependent on the supply of (premasticated) meat for adequate development.

Foraging shaped social structures, cooperation, and tool use, leading to technological innovations that improved dietary breadth. As humans dispersed globally, they adapted to diverse ecosystems, developing unique dietary patterns. Already one million years ago, during the Middle Pleistocene Transition, Homo erectus populations expanded into various African and Eurasian steppe-desert regions and beyond. In arid or icy environments, where plant resources were limited, humans relied heavily on large herbivores, prioritizing fatty cuts of meat. In tropical regions, diets incorporated more fruits, tubers, seeds, and nuts, while coastal populations included seafood and marine fats.

Cooking, fermentation, and other forms of processing improved the safety, digestibility, and nutrient availability of foods, further diversifying diets even within similar environments. Seasonal variations also played a role, with leaner times necessitating a reliance on preserved foods. Despite these variations, ancestral diets typically included a mixture of plants and animal-sourced foods, with macronutrient ratios tailored to local resources. In cold periods of the Eurasian Paleolithic, putrified meat and fish may have provided substantial nutrition as well. Such dietary flexibility enabled humans to thrive in a wide range of environments as dietary generalists. As a broad-spectrum species, the ability of humans to exploit a wide range of animal and plant foods via complex processing marked a major threshold in hominin evolution, and was a key driver of our global colonization of new environments. 

When we talk about a ‘natural’ diet, we are therefore really talking about an ever-changing buffet, tailored by time and place, rather than about a fixed menu. That said, and as is valid for all animals, there are some physiological boundaries that need to be respected. Understanding evolutionary diets and the biological limits of human nutrition can clue us in on what is good for us and what is not. Such knowledge also helps keep modern misconceptions about food in check. Today, the ability to thrive on plant-heavy diets long-term is not universal. It varies with genetic differences in lipid metabolism, brain function, and the conversion of plant precursors into bioactive forms. Notably, APOE ε4 carriers appear more dependent on animal-derived nutrients, likely a legacy of ancestral hypercarnivory, which can contribute to health issues in modern low-meat environments.

After transitioning into more open ecosystems, some three million years ago, hominins increasingly relied on aggressive scavenging. Grassland-derived nutrients, especially those from meat, fat, marrow, and organs, thus entered the ancestral diet, at first probably in modest amounts. A turning point was reached when improved hunting skills enabled access to large herbivores. The earliest evidence of stone-tool-assisted megafaunal consumption by hominins traces back to 1.8 million years ago, based on the discovery of modified elephant bones. At this point, early humans seem to have strategically adaptated to megafaunal resources, likely with profound implications for social organization. 

One million years ago, Homo erectus began to expand into the arid steppe-desert regions of Africa and Eurasia, acting as flexible ecological generalists. Both thermal and non-thermal processing helped to diversify dietary breadth. The controlled use of natural fire by hominins dates back 800,000 years ago or more, which eventually evolved into fire-making technology, at least 400,000 years ago. 

At least some of the upper-Paleolithic diets became dominated by red meat and fat, with mammoth protein comprising up to two-thirds of the intake of Neanderthals and early ‘modern humans’ in certain regions of Eurasia. Their ability to process and store large amounts of meat allowed them to manage seasonal shortages and enabled temporary group aggregations. However, the extinction of megafauna eventually pushed humans toward smaller, faster prey, driving advancements in agility and hunting techniques. 

During the late stages of the Pleistocene, humans adapted to ecological challenges by diversifying their diets to include more eggs, fish, seafood, and plants. The shift toward smaller game required greater precision, planning, and cooperation, advancing social complexity and innovation. Long-range weapons and improved food processing techniques also enhanced food security. 

Probably 30-70% of the caloric intake of early 'modern humans' came from animals, but this may have been higher in areas with mega-herbivores and during glacial conditions. Homo habilis likely consumed only around 10%, being still close to the Australopithecus lineage. For the obligate bipedal and larger-brained Homo erectus, arguably the first true representative species of Homo, the contribution may have been 60% or more, and for Homo neanderthalensis even up to 80%. Nonetheless, landscapes and food sources may have been more diverse and with a higher access to plants than often assumed, even in extreme cold conditions.

Populations were nonethless mostly heavily carnivorous in the presence of megafauna. As an example, the Clovis culture may have obtained up to 95% of calories from large herbivores, such as mammoths. After the megafauna extinction, especially during the Mesolithic ‘Broad Spectrum Revolution’, diets became more diversified while more sophisticated processing enhanced the role of foods like tubers and grains. Macronutrient ratios differed based on ecological factors, with some diets being low in carbs and high in protein, while others incorporated more starches. In any case, animal-sourced foods were essential in all pre-agricultural diets.

On average, modern foragers still derive more than half of their energy from hunting and fishing. In cold environments this even reaches higher shares (>90%), while the caloric budget is dominated by plants for only a minority of groups. Meat and animal fat consumption ranges from 5% to 90% of total caloric intake, with annual intake levels of 40-650 kg per person, depending on the group and region.

Taken together, it’s factually wrong to argue that today's consumption of red meat and animal fat is ‘unnatural’ or ‘unprecedented', even in wealthy countries. During 99% of human existence, our ancestors likely consumed more of these foods per person than we do now.