Fire and Shelters The control of fire and the building of durable shelters were critical means by which mid-Pleistocene hunter-gatherers altered their immediate environment and this also occurred long before the emergence of agriculture. The oldest definitive hearths have been dated at approximately 790 ka (Goren-Inbar et al., 2004), and shelters that were sufficiently durable to be preserved in the archaeological record date from approximately 400 ka (deLumley, 1969; Schick and Toth, 1993). The construction of hearths and shelters enabled hominins to modify the temperature of their immediate surroundings, alter the digestive properties of cooked food, and to distance the group from harsh conditions beyond the shelter. These developments coincided with a period of heightened amplitude of glacial/interglacial oscillations, and thus may reflect the ways in which altering the immediate environment proved beneficial physiologically to individuals and socially to groups (Potts, 1996b). Ultimately, the use of fire also led humans, mainly after 100 ka, to modify entire landscapes as a means of hunting or land clearance to promote new plant growth (e.g., Lentz, 2000; Miller et al., 2005).
Sophisticated Symbolic and Cognitive Behavior The evolution of complex mental capabilities and language had a strong impact on how our species interacted with its surroundings. These developments provided an adaptive advantage in Homo sapiens by enabling social groups to trade resources over long distances and to cope with variations in food, water, and other critical resources in the face of climate change. These cognitive capabilities are indicated by early symbolic artifacts, such as pigments used for coloring, simple etching of objects, and the presence of decorative shell beads. These types of objects indicate an ability to code information symbolically—the essence of language. These artifacts first occur in the African archeological record between 285 ka and 70 ka, associated with the early evolution of Homo sapiens (Barham, 2002; Henshilwood et al., 2002; d’Errico et al., 2005). By approximately 130 ka, artifacts made from rocks from at least 300 km away suggest that human social networks were sufficiently complex to engage in long-distance exchange of high-quality stone and other resources (McBrearty and Brooks, 2000). By at least this date, therefore, our species manifested complex mental behavior and highly coordinated social activity. These developments laid an important part of the foundation for large-scale human impacts such as agriculture, trade, and cities, which have profoundly altered the relationship between humans and natural environments.
The major features of human evolution and the major features of Earth’s climatic evolution over the past 8 million years can be integrated to form a chronological summary, summarized in Table 2.1. This provides the context for the recommendations for the future research and outreach activities that are presented in subsequent chapters.