There is no evidence for behaviorally-limited early homo sapiens

(written by Lawrence Krubner, however indented passages are often quotes)

Here is an essay that captures much of what I’ve been thinking these last few years about human evolution. It is impossible to come up with a model that cleanly maps biological evolution to technological evolution. Therefore, it is probably better to assume that technological innovations, and retreats, represent variability in behavior, rather than “progress” in biology. There is no uniform trend to technology. If there is a trend in human evolution, it is toward a greater allowed degree of behavioral variability, and that is all.

In order to better understand human prehistory, I recommend another approach, one that focuses on behavioral variability. This trait, easily observed among recent humans, is becoming more apparent in the archaeological record for early Homo sapiens. Prehistoric people lived in different ways in different places at different times. We must seek out and explain those differences, for, in evolution, only differences matter. Thinking about prehistoric human behavioral variability in terms of various adaptive strategies offers an attractive way to explain these differences. But first, we need to discard an incorrect and outdated idea about human evolution, the belief that prehistoric Homo sapiens can be divided into “archaic” and “modern” humans.

…In fact, fossil evidence threatening the Upper Paleolithic revolution hypothesis emerged many decades ago. At about the same time the Paleolithic framework was developed during the 1920s and 1930s, European-trained archaeologists began searching for human fossils and artifacts in the Near East, Africa and Asia. Expatriate and colonial archaeologists such as Dorothy Garrod and Louis Leakey expected that the European archaeological record worked as a global model for human evolution and used the European Paleolithic framework to organize their observations abroad. Very quickly, however, they discovered a mismatch between their expectations and reality when Homo sapiens remains outside Europe were found with Lower or Middle Paleolithic artifacts. Archaeologists started assuming then that the remains dated to periods just before the Upper Paleolithic revolution. But in fact, those discoveries, as well as more recent finds, challenge the notion that the revolution ever occurred.

Early Homo sapiens fossils in Africa and Asia are associated with “precocious,” or unexpectedly early, evidence for modern behaviors such as those seen in the European Upper Paleolithic. They include intensive fish and shellfish exploitation, the production of complex projectile weapons, the use of symbols in the form of mineral pigments and perforated shells, and even rare burials with grave goods in them. But as Erella Hovers and Anna Belfer-Cohen of The Hebrew University of Jerusalem argued in a chapter of Transitions Before the Transition, “Now You See It, Now You Don’t—Modern Human Behavior in the Middle Paleolithic,” much of this evidence is recursive. It is not a consistent feature of the archaeological record. Evidence for one or more of these modern behaviors appears at a few sites or for a few thousand years in one region or another, and then it vanishes. If behavioral modernity were both a derived condition and a landmark development in the course of human history, one would hardly expect it to disappear for prolonged periods in our species’ evolutionary history.

For me, the most surprising aspect about the debate regarding when Homo sapiens became human is that archaeologists have not tested the core hypothesis that there were significant behavioral differences between the earliest and more recent members of our species. Because modernity is a typological category, it is not easy to test this hypothesis. One is either behaviorally modern or not. And, not all groups classified as behaviorally modern have left clear and unambiguous evidence for that modernity at all times and in all contexts. For example, expedient and opportunistic flintknapping of river pebbles and cobbles by living humans often creates stone tools indistinguishable from the pebble tools knapped by Homo habilis or Homo erectus. This similarity reflects the nature of the tool-making strategies, techniques and raw materials, not the evolutionary equivalence of the toolmakers. Thus, the archaeological record abounds in possibilities of false-negative findings about prehistoric human behavioral modernity.

One way to gauge early Homo sapiens’ behavioral variability is to compare their lithic technologies. Lithics, or stone tools, are nearly indestructible and are found everywhere hominins lived in Pleistocene times. Stone tools do not tell us everything we might wish to know about prehistoric human behavior, but they are no less subject to the selective pressures that create variation in other types of archaeological evidence. Lithic artifacts made by recent humans are more complex and variable than those associated with early hominins. Early Paleolithic stone tools are more complex and variable than those made by nonhuman primates. Thus, there is reason to expect that analysis of these tools will produce a valid signal about early Homo sapiens’ capacity for behavioral variability. Eastern Africa is an especially good place in which to compare early and later Homo sapiens’ stone technology because that region preserves our species’ longest continuous archaeological record. Restricting this comparison to eastern Africa minimizes the complicating effects of geographic constraints on stone-tool technology.

…Nor is there any reason to believe that behaviorally archaic Homo sapiens ever did exist. If there ever were significant numbers of Homo sapiens individuals with cognitive limitations on their capacity for behavioral variability, natural selection by intraspecific competition and predation would have quickly and ruthlessly winnowed them out. In the unforgiving Pleistocene environments in which our species evolved, reproductive isolation was the penalty for stupidity, and lions and wolves were its cure. In other words: No villages, no village idiots. If any such cognitive “winner take all” wipeout event ever happened, it was probably among earlier hominins (Homo ergaster/erectus or Homo heidelbergensis) or during the evolutionary differentiation of our species from these hominin ancestors.

Dividing Homo sapiens into modern and archaic or premodern categories and invoking the evolution of behavioral modernity to explain the difference has never been a good idea. Like the now-discredited scientific concept of race, it reflects hierarchical and typological thinking about human variability that has no place in a truly scientific anthropology. Indeed, the concept of behavioral modernity can be said to be worse than wrong, because it is an obstacle to understanding. Time, energy and research funds that could have been spent investigating the sources of variability in particular behavioral strategies and testing hypotheses about them have been wasted arguing about behavioral modernity.

Anthropology has already faced this error. Writing in the early 20th century, the American ethnologist Franz Boas railed against evolutionary anthropologists who ranked living human societies along an evolutionary scale from primitive to advanced. His arguments found an enthusiastic reception among his colleagues, and they remain basic principles of anthropology to this day. A similar change is needed in the archaeology of human origins. We need to stop looking at artifacts as expressions of evolutionary states and start looking at them as byproducts of behavioral strategies.