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HOME > PAST ISSUE > July-August 2009 > Article Detail

FEATURE ARTICLE

Human History Written in Stone and Blood

Two bursts of human innovation in southern Africa during the Middle Stone Age may be linked to population growth and early migration off the continent

Zenobia Jacobs, Richard G. Roberts

Figure 1. Artifacts left behind in southern AfricaClick to Enlarge Image Even by archaeological standards, Blombos Cave is a modestly sized shelter. Yet artifacts recovered from just 13 cubic meters of deposit inside transformed our understanding of when our species developed behavioral attributes we associate with “modern” humans. From this cramped hole in a sandstone cliff on the Southern Cape coast of South Africa, Christopher Henshilwood and his colleagues unearthed evidence of symbolic expression, in the form of abstract designs (carved ochre bars) and personal ornaments (shell beads) at least 70,000 years old. That is more than 35,000 years before anything comparable emerged in Europe.

When these discoveries were first announced earlier this decade, they stood out as extraordinary and provocative—at odds with the prevailing wisdom about the time and place of emergence of symbolic behavior, a trait unique to Homo sapiens . Our modern anatomical features can be traced back almost 200,000 years, based on fossilized remains found in Ethiopia, but the making of the modern mind apparently lagged behind by more than 100,000 years. The remarkable finds at Blombos raised several intriguing questions. What triggered this watershed event in human prehistory? How geographically widespread was it? Did it occur simultaneously elsewhere in sub-Saharan Africa? And what role, if any, did such innovations play in the first steps of the worldwide dispersal of our species?

Important clues come from the stone toolkit that accompanied the crosshatched ochres and deliberately perforated shells at Blombos. Stone tools commonly are the most ubiquitous items at archaeological sites because they survive longer than animal or plant remains. Archaeologists pay close attention to their method of manufacture and how they might have been used. Although much less heralded than engraved ochre and shell beads, the Middle Stone Age deposits at Blombos contained an important assemblage of stone tools known as Still Bay points. These finely shaped lanceolate, or narrow, points are flaked on both sides and probably formed spearhead parts. Discovered in 1866 by Sir Langham Dale near Cape Town, they were among the first type of stone tool described in South Africa. A. J. H. Goodwin, the father of South African archaeology, was the first to appreciate the technological sophistication of this stone-tool industry.

The Still Bay cultural industry is now widely viewed as a phase of precocious and innovative technology within the Middle Stone Age of Africa, preceded by 200,000 years of much less sophisticated stone toolkits. It was followed by another episode of technological innovation—the Howieson’s Poort industry—that includes bladelike tools made blunt on one side and attached to a wooden handle to produce a composite weapon. Like the Still Bay, Howieson’s Poort vanished too. Technology of similar sophistication does not appear again in the archaeological record until the Later Stone Age in Africa and the Upper Paleolithic in Europe, many tens of millennia later.

Figure 2. 72,000-year-old relics from Blombos Cave The importance of the Still Bay and Howieson’s Poort lies not only in their enhanced technological sophistication with what looks like hunting tools, but also with the range of associated innovative behavioral artifacts. These include the Blombos finds in the south, engraved ochre at Klein Kliphuis and decorated ostrich eggshells at Diepkloof in the west, and bone points and shell beads at Sibudu to the east. These relics of human cognitive advancement imply that an increasingly complex technological and social organization coincided with what some archaeologists now consider a period of expanded human population size and settlement density in Africa. Comparably sophisticated stone-tool technologies also existed in North Africa (most notably the bifacially flaked and stemmed Aterian projectile points found throughout the Maghreb) and, possibly, in East Africa, the suspected launching ground for early human forays off their native continent. Personal ornaments occasionally have been found at those sites as well, including perforated ostrich eggshell beads and pierced shells of marine gastropods.

Efforts to compare the timing of these technological and behavioral innovations to those in southern Africa have long been frustrated by uncertainties in the dating of evidence from each region. As a result, identifying the time and place of the emergence of modern human behavior has eluded us. So have the reasons for, and the immediate consequences of, our ancestors becoming “human.” Solving these puzzles will require more finely resolved dating and chronologies for key archaeological sites across the continent. We started this quest with a systematic dating study of several sites in southern Africa. Our results hint at the possible role of population expansions in Africa as a trigger for these Stone Age innovations—and, maybe, for early migrations out of Africa about 60,000 years ago.




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