An immensely long time ago, somewhere between two and three million years in the past, some of our earliest hominid ancestors, known as Homo erectus, began to explore new foraging grounds far beyond the savannas of tropical eastern Africa. Some of these explorations may have been driven by simple curiosity, others perhaps by population pressure that stretched resources too thin in the familiar home territory. Others may have been propelled by the desire to escape conflicts. If Homo erectus had much in common with modern human beings, a complex range of economic and sociocultural motivations may well have propelled the early explorations.

Some groups dispersed widely into the vast expanses of Afro-Eurasia. There they made tools and clothing and colonized a surprisingly wide swath of tropical and subtropical landscapes. These early migrants had extremely modest and primitive technologies, and it is remarkable that any of their remains and artifacts have survived. Much later, around 300,000 to 200,000 years ago – at roughly the same time that modern Homo sapiens emerged in tropical Africa – one of our hominid cousins, Homo neanderthalis, was colonizing parts of western Eurasia. Over time, across broad reaches of Eurasia, Homo erectus and Homo neanderthalis both succeeded in a widening array of physical environments and climatic conditions. Surprisingly, these broadening experiences were not to be the root source of the accelerated cultural and physical evolution that distinguishes modern humankind.