Welcome to Chapter 6, the world of a million years ago. We are now holding one gold bar of time in our hands. It’s time to learn another round of technical terms. The present-day geological period is called the Quaternary. The lengthy first epoch of the Quaternary, the Pleistocene Epoch, lasted from 2.6 MYA all the way up to Chapter 4. These terms no longer gibe very well with their etymologies. The term “Quaternary” originally meant “fourth” and “Pleistocene” meant “the most recent”. Now they have both been redefined to coincide with Earth’s current cycle of ice ages.
For the first time in Chapter 6, we encounter time scales that are used by archaeologists instead of geologists. Archaeology is the study of humans and their artifacts. In fact, archaeologists define “humans” as distinct from earlier hominin animals by their use of tools. The first tools were made of stone, so the earliest archaeological age goes by the well-known moniker of the Stone Age, or in Latin Paleolithic. Of course, scientists like to divide and subdivide their timelines. Chapter 6 coincides almost perfectly with the old or “lower” Paleolithic. This layer encompasses the three oldest phases or “industries” of stone technology. Those few stone tools known from 3 MYA are called Lomekwian. The tools in use 2 MYA belong to the Oldowan Industry, and those from 1 MYA fall into the Acheulean Industry. Not all scientists agree that these classifications are meaningful, 1 but they are the preferred archaeological terms for now.
As in earlier chapters, planet Earth itself set the stage for its natural history. Climate and geography directed plant evolution, which affected animal life and human ancestry. For the last few million years, global climate has been characterized by a series of ice ages. Section II of this chapter discusses the overall causes and effects of these ice ages. For our purposes, the most important consequence was the evolution of what we now call the Homo genus – early humans. The paleontological and archaeological record of that evolution – the “hard” data of bones and stones – is the subject of Section III.
Chapter 7 was the point of departure for the hominin clade from the rest of the great apes. The commonalities of humans with other apes were discussed in Chapter 7. Chapter 6 focuses on the differences, which are harder to date but are reserved for this chapter as a practical matter. Aside from the skeletal anatomy, Section IV discusses the major soft-tissue and behavioral traits that set the hominins and humans apart from chimpanzees.
- John Shea, Stone Tools in Human Evolution, Cambridge University Press (2017). ↩
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