Leiden archaeologists uncover earliest evidence of plant food processing
A new study carried out by Leiden archaeologists Hadar Ahituv and Amanda Henry, together with international colleagues, reports the identification and analysis of 650 starch grains preserved on basalt percussive tools (anvils and hammerstones) found at an early Middle Pleistocene site in Israel. These 780,000-year-old starch grains are the earliest reported from an archaeological context. The find gives us new insights into the dietary habits of our early ancestors.
Narratives
Narratives about the dietary habits of our early ancestors are often used as a justification for present-day diets. These emphasize the importance of animal foods, and only rarely have plants been considered as drivers of human evolution. Plant foods are less archaeologically visible, and it is seldom recognized that their consumption involved foraging skills, processing sequences, and advanced toolkits, making them an essential component in our evolutionary history. Furthermore, studies of modern hunter-gatherer societies indicate that plant foods occupy a central place in the diet, especially starch-rich plants. These played an important role in human evolution, as digestible carbohydrates were essential to support the increased metabolic demands of a growing brain. When processed (grounded, cooked), starch can increase energy availability as a source of preformed glucose.
Starch grains
The 780,000-year-old starch grains from the early Middle Pleistocene waterlogged site of Gesher Benot Ya’aqov are the earliest reported from an archaeological context. Previous excavations at the site revealed many occupational levels with rich assemblages of stone tools (basalt, flint, limestone), animal bones (e.g., elephants, fallow deer, fish) and plant remains (acorns, grains, seeds and fruits). Throughout the extraction process of the starch grains, other microscopic findings were discovered that include pollen grains, diatomaceous algae (diatoms), phytoliths, animal hair (rodents), and feathers (waterfowl).
Analyses of the starch grains resulted in the identification of acorns, grass grains, yellow waterlily rhizomes, legumes seeds, and water chestnuts (currently extinct in the region). The identified plants vary in their habitat (lake, lake edge, and upland areas), in their gathering and processing modes, and in their seasonality, suggesting that they were collected, processed, and consumed throughout the year.
The study indicates the advanced cognitive abilities of our early ancestors, including their ability to collect plants from a wide range of habitats, from varying distances, during different seasons, and to mechanically process them using percussive tools. The proximity of the tools to hearths indicates the possibility of using fire as an additional food processing step.
Overall, this project indicates that plants have been an essential part of the human diet since our earliest ancestors. ’All animals learn which plants are edible and which are not. At some point in our evolutionary history, our ancestors learned how to process potentially toxic plants to make them edible. This ability was a key element of our success as a species.’ explains Prof. Henry.
International Team
The research is part of Dr. Hadar Ahituv's doctoral dissertation written at Bar-Ilan University and co-supervised by Prof. Henry and Dr. Nira Alperson-AfilThe study is multidisciplinary and involved several academic institutions: Bar-Ilan University (Prof. Nira Alperson-Afil, Dr. Yoel Melamed), the University of Haifa (Dr. Hadar Ahituv), Leiden University (Prof. Amanda Henry), the Netherlands, the Hebrew University of Jerusalem (Prof. Naama Goren-Inbar), and other research institutes.