Trees and ladders: a critique of the theory of human cognitive and behavioural evolution in palaeolithic archaeology

The modern biological model of (human) evolution is that of a branching tree. As the evolution of cognition can be expected to be closely tied to the biological evolution of the brain, it should be represented by a branching tree model as well. Instead, a linear, ladder-like model is used to represent cognitive evolution in palaeolithic archaeology. This mismatch between models for phylogenetic and cognitive evolution is largely the result of the way two primary frames of reference are employed by archaeologists. At the base of the ladder-model is a primate-like cognition, modeled after primate studies. At the top of the ladder is “modern behaviour”, largely inspired by ethnographic models. These are put in opposition, representing the two ends of what by definition becomes a linear line. The structure of this evolutionary model is not fundamentally based in either modern evolutionary theory or the archaeological record. Instead, it structures the archaeological record while itself being structurally immune to constraints from data. It forces all types of behaviour that are not considered fully “modern” to assume a position at a lower cognitive level. Adopting a branching tree model has serious implications for our views on hominin cognition and the meaning of being “behaviourally modern”. In a branching model, “modern behaviour” no longer has a unique status as being by necessity the most sophisticated level of cognition. It becomes just one of several possible expressions of highly sophisticated cognition. Not only is such a model in closer agreement with models of biological evolution, but another advantage is that it can be structured to pertinent archaeological data and is actually testable with archaeological data. The challenge it involves is that ways have to be devised to account for unique cognitive expressions that are not covered by the existing framework of ethnography and primatology. In addition, notions about the “superiority” of “modern behaviour” over other forms of cognitive expression have to be abandoned.