The diet of known human ancestors varies dramatically over time. Strictly speaking, according to evolutionary anthropologists and archaeologists, there is not a single hominin Paleolithic diet. The Paleolithic covers roughly 2.8 million years, concurrent with the Pleistocene, and includes multiple human ancestors with their own evolutionary and technological adaptations living in a wide variety of environments. This fact with the difficulty of finding conclusive evidence often makes broad generalizations of the earlier human diets very difficult. Humans' pre-hominin primate ancestors were broadly herbivorous, relying on either foliage or fruits and nuts and the shift in dietary breadth during the Paleolithic is often considered a critical point in hominin evolution. A generalization between Paleolithic diets of the various human ancestors that many anthropologists do make is that they are all to one degree or another omnivorous and are inextricably linked with tool use and new technologies.
Background
Due to the variety of environments inhabited, physiologies of the humans and human ancestors alive during the Paleolithic over 2.8 million years, we can’t ascribe a single set diet to any species, regional or cultural group. Larger brain sizes required a greater caloric intake. In colder climates meat might be necessary due to the decreased availability of plant based foods, and in hotter tropical climates a wider range of plants would be available.
Evolution of hominins
Recent estimates of the last common ancestors of humans and chimpanzees are around 12 million years ago. After this split the first bipedal hominins appeared around 4 million years ago in the genus Australopithecus. The first appearance of genus Homo takes place around 2.8 million years ago with Homo habilis, followed by Homo erectus at around 1.8 million years ago, Homo neanderthalensis by 400,000 years ago and finally the first appearance of Homo sapiens by 200,000 years ago. In each new species of hominin, particularly genus Homo there is a general trend of increasing brain size and decreasing dentition, these patterns are inextricably linked with an evolving diet.
Lines of evidence to uncover the diet of human ancestors There are numerous difficulties in detecting and understanding the ancient diet of human ancestors. The Paleolithic begins around 2.6 million years ago and ends only around 12,000 years ago with the onset of the Holocene and Neolithic. The enormous time scale, variable environments inhabited by human ancestors and issues with preservation ensure that direct evidence is often very difficult to come by.
Evolutionary anthropologists who study the evolution of human origins and diet use a variety of methods to determine what human ancestors ate. As a starting point comparative analysis of the diets of humans closest living relatives, great apes such as chimpanzees, bonobos and other great apes, though these comparison are limited. Through environmental reconstruction of the areas ancient humans lived, inferences of available resources can be made. A common method of analysis is through the study of dentition and toothwear, as different foods will leave different markers that can be studied. There is also direct archaeological evidence, different types of tools would be used to process and consume different types of food and often be associated with faunal remains and evidence of fire. Human coprolites can also reflect direct evidence of diet.
More recent techniques have been introduced such as carbon isotopic analysis of recovered bones, which can be used as direct evidence of diet, and life history traits. An example would be the expensive tissue hypothesis, linking a decrease in gut size with an increase in brain size. Recently genetic studies of differences between Homo sapiens and other related hominins to determine adaptations related to diet.
Hominin diet before the Paleolithic Generally speaking, inferring feeding adaptations in fossil hominins is not a simple task, and hence diet reconstructions have relied on diverse techniques (e.g. microwear, stable isotopes, functional morphology, etc.) that have provided different or even contradictory results. The direct predecessors to genus Homo, Australopithecus are thought to have broadly been frugivores or herbivores. The dental and jaw morphology of Australopithecus afarensis have often been assumed to indicate a diet of harder brittle foods, however tooth wear analysis from some specimen reflect a diet of tough grasses and leaves. This is corroborated by stable carbon isotopic evidence indicating the consumption of plants found along riversides and under tree cover. A recent study that analysed several hominin taxa has shown that they were probably not hard-food specialists, most likely relying on a softer diet.
Homo naledi, Homo habilis, Homo floresiensis and Homo erectus
Homo naledi Almost half of H. naledi teeth have one or more chips on the enamel surface, caused by teeth coming into contact with hard foods or environmental grit during life. These antemortem enamel fractures are predominantly small and on the surfaces between molars, suggesting either a small hard dietary item was commonly consumed, or, more likely, environmental grit was incorporated into their diet when eating foods such as tubers. Two other studies support the suggestion that H. naledi consumed large quantities of small hard objects, most likely in the form of dust or grit. Crown shape supports this finding, with taller crowned and more wear resistant molars, potentially evolving to protect against abrasive particles. Microwear on the molars of H. naledi also suggests they regularly consumed hard and abrasive items. Overall, it is likely H. naledi differed substantial from other African fossil hominins in terms of diet, behaviour, or masticatory processing.
Homo habilis By 3 million years ago the broad pattern of human dentition was in place with reduced canines and a jaw morphology implying heavier chewing. Stone tools and butchered animal remains dating to 2.6 million years ago have been found together in Ethiopia. This finding provides both the clearest evidence of meat eating by early human ancestors and the association of earliest stone tools with the butchering of animals for meat and marrow. This co-occurrence of stone tools is clearly linked with the butchering of animals and earliest identifiable appearances of Homo habilis. Tooth wear from Homo habilis indicates a relative lack of hard foods such as nuts, tubers or other hard brittle plant material being consumed. This is not to say that no tougher foods were eaten by H. habilis, only that it was likely not a regular part of the diet. By contrast, Homo erectus teeth generally reflect a much higher degree of wear, indicating tougher plant foods being eaten. While likely able to consume a variety of plant and animal resources, it seems that H. habilis was not able to exploit the wide array of resources and ecological niches its descendants would be able to.
Homo erectus In contrast to Homo habilis, H. erectus left its ancestral environment of Africa and spread through much of the old world. Homo erectus appears to have avoided other large predators. Several interpretations of Homo erectus diet have been made, usually contrasting between primarily plant based foragers and scavengers or opportunistic hunters. However, as H. erectus dispersed across Eurasia some behaviors in some areas appear to have changed. The trajectory of diets between Homo habilis and Homo erectus can be described as a diversification of diet as Homo erectus spread within Africa and beyond into Asia. Meat played a critical role in the evolution of H. habilis, but as Homo erectus evolved the diet broadened to include tougher foods that H. habilis did not consume regularly. A broad diet alone however is not Homo erectus''' sole contribution to evolution of the human lineage. Genetic evidence of reduced jaw muscles implies the adoption of cooking by humans prior to the branching of H. sapiens and H. neanderthalensis, placing the first use of fire for cooking firmly during the time of Homo erectus. Fire presents clear advantages to a species diet, in that cooking allows a greater range of foods to be eaten and improves the caloric content of both animal protein and plants. Another hypothesis is that H. erectus used tools to slice up their food even before they started to cook it, making it easier to chew.H. erectus cut, chewed way through evolution - Science News
Homo floresiensisHomo floresiensis is thought to have diverged from humanity's ancestral branch prior to the evolution of Homo erectus. The direct ancestor of Homo floresiensis is currently thought to be Homo habilis, but this is subject to change with new information. Tooth wear from Homo floresiensis implies a tough, fibrous diet requiring powerful mastication. There is some evidence of meat eating associated with Homo floresiensis, but current evidence indicated that a plant based diet dominated. The specific plant species available to H. floresiensis is currently unknown. This complicates H. floresiensis relationship to H habilis, due to the latter’s association with intensive meat eating diet. That being the case, more than enough time passed for H. floresiensis diet to specialize to its given environment.
Homo heidelbergensis and Homo neanderthalensis Homo heidelbergensisHomo heidelbergensis, the likely predecessor of Homo neanderthalensis, has few direct clues to its diet. Two adult incisors, likely from H. heidelbergensis have been found in England in an environment that at death would have been a spring fed wetland. The teeth themselves are heavily worn, implying heavy wear in the individual’s diet. Wooden spears dating to between 380,000 and 400,000 years BP were found in Germany, indicating that H. heidelbergensis was a big game hunter with sophisticated technology.
Homo neanderthalensis