Over millions of years, the human lineage evolved from wetland forest-dwelling primates to open grassland and forest-dwelling bipedal hominins, of which homo sapiens is the only remaining species. Several key anatomical adaptations occurred during this transition, many of which were driven by the consumption of animal-source foods (ASF), including meat. Anthropological evidence from multiple fields of research has repeatedly confirmed the critical role of ASF consumption in the anatomical, cognitive and social development of our species. 

As early as four million years ago, early bipedal hominins scavenged ASF, as evidenced by cut marks on animal bones, examination of the stable isotope composition of ancient hominin remains, and findings from physiological and paleo-anthropological research. 

Then, the transition towards proactive exploitation of large animals marked a key milestone in early human development. This dietary shift marked a transition from a predominantly forest dwelling frugivorous diet to an open rangeland existence. It drove numerous biological adaptions, including significant increases in brain size and alterations to gut structure as the more nutrient dense and bioavailable ASF in the diet enabled a reduction in gut size and gave our bodies the ability to support the energy demand of a larger brain. This process of evolutionary adaptation meant the human gut composition is now more aligned with a wolf, lion or bear than with the great apes. 

Other evolutionary adaptions relate to the relatively early weaning of human infants compared to the great apes. Research suggests that the prolonged early brain growth of human infants, which is the neurological foundation for human intellectual ability, requires more energy than can be sustained by human mothers’ milk alone. Researchers suggest the introduction of adult foods at a young age was an adaptation response supporting brain development, despite the additional survival risks of weaning infants. In this way, evolutionary selection’s primary direction favoured the intellectual development of the new generations, rather than simply survival of the body.