But evidence for the emergence of behaviorally modern humans is murkier — and controversial. Recent discoveries establish that the Homo sapiens groups who arrived in Europe some 45,000 years ago had already attained the self-awareness, creativity and technology of early modern people. Did this behavior come from Africa after gradual development, or was it an abrupt transition through some profound evolutionary transformation, perhaps caused by hard-to-prove changes in communication by language?
Now, the two schools of thought are clashing again, over new research showing that occupants of Border Cave in southern Africa, who were ancestors of the San Bushmen hunter-gatherers in the area today, were already engaged in relatively modern behavior at least 44,000 years ago, twice as long ago as previously thought. Two teams of scientists reported these findings Monday in the journal Proceedings of the National Academy of Sciences.
Since this early date for the San culture is close to when modern humans first left Africa and reached Europe, proponents of the abrupt-change hypothesis took the findings as good news.
Richard G. Klein, a paleoanthropologist at Stanford University, said in an e-mail from South Africa that the new evidence “supports my view that fully modern hunter-gatherers emerged in Africa abruptly around 50,000 years ago, and I remain convinced that the behavior shift, or advance, underlies the successful expansion of modern Africans to Eurasia.”
Dr. Klein was not an author of either of the papers, but was cited as editor of the main report by a group led by Francesco d’Errico of the University of Bordeaux in France.
In their research, Dr. d’Errico and colleagues re-examined organic artifacts from Border Cave and their refined radiocarbon ages, concluding that “key elements of the San material culture” place “the emergence of modern hunter-gatherer adaptation, as we know it,” to more or less 44,000 years ago.
Previous discoveries revealed that other cave dwellers in southern Africa were experimenting with pigment use, body adornment, and advanced stone and bone tools more than 75,000 years ago, but that many of these artifacts seemed to disappear by 60,000 years ago. Dr. d’Errico’s group said this suggested that “modern behavior appeared in the past and was subsequently lost before becoming firmly established.”
At Border Cave, which lies in South Africa near the border with Swaziland, the international team of scientists analyzed a wealth of organic artifacts in the sequence of their development: bead and shell ornaments; notched bones, perhaps for counting; bone awls; thin bone arrowheads tipped with poison from toxic castor bean oil; and residues of beeswax, resin and possibly egg, which were probably used for hafting wooden handles to stone or bone tools. This may have been one of the earliest known human uses of beeswax.
Regardless of the contending evolutionary interpretations, Chris Stringer, a paleoanthropologist at the Natural History Museum in London, who was not involved in the research, said the evidence from Border Cave provided “the clearest links yet found between Stone Age materials more than 20,000 years old and the culture of extant hunter-gatherers.”
Dr. Stringer said the findings “suggest at least a degree of continuity” in the development of modern human behavior over the last 40,000 years or so.
In a companion article in the journal, researchers led by Paola Villa of the University of Colorado in Boulder described the cave’s stone tools and evidence of changes in hunting technology, including what appeared to be the bow and arrow. Dr. Villa said the contrasting cultures between these people and those who arrived in Europe about this time, leaving graphic traces on cave walls, showed that “the two regions chose very different paths to the evolution of technology and society.”
Asked if the new research strengthened the case for Dr. Klein’s hypothesis, Dr. d’Errico said: “I am not sure it does. Apart from Australia, the spread of modern humans outside Africa is not well documented archaeologically and may have been a more complex process than just a single shot.”
In an earlier paper written with Dr. Stringer, Dr. d’Errico said that in his view, present evidence “does not support a gradualist scenario nor a revolution scenario, but a nonlinear process during which key cultural innovations emerge, are lost and re-emerge in different forms before being finally adopted.”
This process, he continued, “does not happen everywhere at the same time,” and the material culture at Border Cave is “not necessarily valid elsewhere.”
Source: NY Times