The Importance of Aquatic Foods and Environments for the Early Hominin Brain

Abstract

Abstract Diet was critical to the growing early Homo brain, which required brain-selective nutrients such as docosahexaenoic acid (DHA), iodine, and iron for growth. Fish and shellfish were optimal sources of these nutrients. The fruit and vegetal diet of the earliest hominins, however, contained few of these nutrients. Early Homo and the australopithecines emerged along with changing environments including spreading grasslands and extreme temperatures. Their requirements for drinking water and shade meant archaeological sites were frequently located near wooded streams and rivers, lakes, and springs, ensuring hominin familiarity with edible wetland vegetation and freshwater-dwelling animals. Archaeological excavations and isotopic evidence indicate that early Homo procured spawning fish, probably crabs and shellfish, and scavenged meat. Fish was an invaluable food in the hot, dry seasons—predictable, easily caught, fatty, and, significantly, containing brain-specific nutrients. Fish—and likely nutritious crabs, shellfish, and scavenged meat—therefore fueled the ongoing encephalization of early Homo (including early H. erectus) and provided hominins with seasonally reliable food sources, complemented by carbohydrate-rich plant foods and scavenged mammal meat. Later in hominin development, consumption of marine food resources similarly provided DHA and other brain-specific nutrients.