We Are What We Ate: The Diets That Fueled Human Evolution

Humans consume more meat than any other primate. We are also the only primate to regularly eat animals larger than ourselves. This is the human predatory pattern, but how, when, and why did this happen? What were the ecological and evolutionary circumstances that positioned our ancestors to become the first primate intruders into the carnivore guild? New fossil and archaeological discoveries dating between 4 – 2 million years ago continue to pull back the curtain on these questions, and new theoretical framing draws from nutritional and ecological literature to examine its consequences even today. The human predatory pattern had impacts across hominin anatomy, technology, and social behavior, starting with the first blow of stone on bone to access the marrow inside. This talk will summarize this new evidence and how it contributes to the changing story of human omnivory.

We humans are unusual in comparison to our primate cousins, regarding our penchant for consuming meat from large animals. Archaeological evidence of stone tools useful for butchery and cut marks on bone fossils indicate that this dietary shift predated the origin of the genus Homo about 2 million years ago.  Such foods are also rich in essential amino acids, certain vitamins like B12 (not made by plants) and trace elements. Iron is essential for almost all life forms, but it is also toxic in excess.  However, Iron is particularly important for women of child-bearing age, and the demands are even greater during pregnancy and lactation.  Elemental iron and iron present in plants are poorly absorbed. In contrast “red meat”, eponymously defined by its rich content of heme iron associated with myoglobin, is much more efficiently utilized, because of the presence of specific heme receptors in the gut––increasing the likelihood of successful pregnancies and breast-feeding in ancestral populations.  However, with the onset of agriculture, animal domestication and major increase in production and consumption, red meat is associated with major diseases such as cancer, atherosclerotic cardiovascular disease, obesity, and type 2 diabetes. Given that red meat is now sought after as prestigious food in most societies, its increasing large-scale production contributes substantially to environmental degradation and climate destabilization. This presentation (including some of our own work) discusses how “red meat”, once a valuable resource—has, in modern times, been partially transformed from “blessing” to a ‘curse”.

The human gut houses trillions of microbes from hundreds of species forming an ecosystem called the microbiome. This ecosystem not only aids digestion and gut health, but is wired into diverse physiological processes including immune system regulation, metabolism, and central nervous system function. Unlike our human genome, our microbiome can adapt to changes in its environment on a timescale ranging from days to weeks with diet being one of the most powerful influences on the microbiome. This plasticity enables adaptations to dietary changes, such as those associated with seasons or migrating into new environments; however, it also represents a vulnerability. Extreme or prolonged dietary change can drive microbial extinctions in the gut microbiome, as well as changes in composition and function that are deleterious to human health. Recent evidence has revealed that humans living an industrialized lifestyle harbor a gut microbiome that is radically different from that of our paleolithic ancestors. Adaptation of the gut microbiome to industrial, highly processed foods has resulted in a deteriorated ecosystem that may be causing and contributing to many chronic metabolic and inflammatory diseases.

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