The transition from plant to meat-based diets implies an increased consumption of fat and protein relative to carbohydrate. Accordingly, modern humans have likely retained these nutritional adaptations to the consumption of meat and starchy plants.
Notably, isotopic carbon analysis suggests that certain types of plants, primarily starchy in-ground tubers (prehistoric potatoes), remained in ancestral diets following this proposed transition. Isotopic nitrogen analysis has suggested that the source of this meat was largely terrestrial animals. Meat is easily masticated compared to plants, removing the need for larger and more powerful mandibles, and its fat content makes it energy-dense, matching higher metabolic demands despite a reduced gut length. Scientists have argued that these morphological changes in hominins were made possible due to a transition from plant to meat-based diets. These two changes are seemingly paradoxical as our brains are metabolically demanding organs, yet a reduced gut length would mean less capacity for absorbing nutrients to fuel a larger brain. Another major morphological development, which occurred alongside brain expansion, is a reduction in gut length. As human evolution progressed, mandibles became more slender while brain size increased, akin to chimpanzees, which eat insects and small mammals in addition to plants. Our earliest hominin ancestor, Australopithecus, evolved approximately 4 million years ago, and is characterized by enormous mandibles (lower jawbones), akin to gorillas, which require their large mandibles to effectively crush plant matter. Similarly, features in hominin ancestors can be compared to evolutionarily related organisms whose diets are well characterized, such as vegetarian gorillas and omnivorous chimpanzees. As an example of this, a crab claw and pair of scissors share form, such that a person unacquainted with crabs but familiar with scissors could infer that a crab uses its claw to cut.
A major source of evidence comes from comparative morphology, which infers function through form. Reconstructing this Paleolithic nutritional environment can provide clues to the diet of our Homo genus ancestors, and what would have comprised the maximally healthy diet. Modern humans are believed to have migrated from Africa only 60,000 to 100,000 years ago, relatively recently in our evolutionary timeline, suggesting that modern humans have retained the nutritional adaptations of these early migrants. Anthropological evidence suggests that the majority of human evolution (approximately 2.5 of 3 million years) occurred in East Africa. Homo sapiens sapiens, the anatomically modern human, evolved from hominin ancestors over a period of approximately 3 million years during the Paleolithic Era. So, what does our evolutionary history tell us about how we should structure our modern-day diets? Examining how the human diet has evolved over time could provide insight into the origins of the diseases of affluence and what an optimal diet entails, as evolution likely selects for diets that maximize nutrition.
#Human evolution timeline free#
The observation that modern hunter-gatherer societies appear to be free from the diseases of affluence has led evolutionary biologists to hypothesize that our stone-age metabolism and modern nutritional environment are poorly matched, fostering the development of these diseases. However, these efforts have been hampered by the complexities of human nutrition. Widespread prevalence of these diseases of affluence has fuelled public interest in determining the optimal human diet. Nutrition plays an important role in so-called “diseases of affluence” such as obesity, diabetes, and cardiovascular disease – now epidemic in developed countries.