The evolution of the human brain may owe as much to fruit and honey as to meat, according to a new Analytical Review. Its findings challenge one of the dominant ideas about our ancestors' diet. “Although animal foods were clearly instrumental, changes in intake of sugars and starches also shed light on human development, health, and disease,” write the authors. “Our modeling provides new perspectives on evolution of the human diet over the course of 4 million years, highlighting the important role of carbohydrates, sugars, and sweetness.” Human evolution is often framed around the growing dietary importance of meat, protein, and omega-3 fatty acids in driving brain growth and development of human traits. However, early hominins likely also consumed substantial amounts of carbohydrates, like natural sugars from fruits and honey, which supplied glucose needed by the increasingly energy-hungry brain and other glucose-dependent tissues. The development of cooking later added starch-rich foods to this carbohydrate supply, while animal foods supported adaptations such as smaller teeth, jaws, and digestive tracts. However, the role of sugars in diets of early humans remains poorly understood.
In this Analytical Review, Jennie Brand-Miller and colleagues argue that carbohydrates were equally as important to our ancestors’ development as the consumption of animal-based foods. By modeling brain and body size alongside metabolic demands over 4 million years of human evolution, Brand-Miller et al. estimate that natural sugars provided roughly 20-35% of total dietary energy intake for much of human evolution. Human anatomy, physiology, and genetic adaptations related to glucose metabolism further suggest that carbohydrate-rich foods helped sustain the exceptionally high energy demands of a growing brain and increasingly active body, with cooked starch becoming important later. Moreover, the authors suggest that seasonal and climatic fluctuations in carbohydrate availability may also have shaped foraging strategies, brain development, and even population survival.
Podcast: A segment of Science's weekly podcast with Jennie Brand-Miller, related to this research, will be available on the Science.org podcast landing page after the embargo lifts. Reporters are free to make use of the segments for broadcast purposes and/or quote from them – with appropriate attribution (i.e., cite "Science podcast"). Please note that the file itself should not be posted to any other Web site.
