Accommodating Opposing Perspectives in the “Modern Human Behavior” Debate

Abstract

Two recent papers in Current Anthropology (Henshilwood and Dubreuil 2011; Shea 2011) highlight a divide between those who still believe that “modern human behavior” can be accounted for by neurocognition and those who claim that this can be better explained by behavioral ecology. Unfortunately, each paper tended to remain within its own terms of reference and did not address the other’s concerns. This may have been because of the perceived incompatibility inherent in the opposing positions, but as is demonstrated below, there is much to be gained by taking a more conciliatory line. If human behavior is signified by an ability to produce a range of artifacts from the “rudimentary” to the more complex, then the flexibility that underwrites this variance has to be specified. Although ecological factors may be able to account for such variance, there must also be some neurocognitive substrate on which this flexibility depends (Hodgson 2010) that is able to define the underlying mechanism involved. It has recently been confirmed that mirror neurons are present in the human brain and are more extensive than in nonhuman primates. These neurons appear to facilitate social interaction (Keysers and Gazzola 2011), and they provide a way of addressing this issue. Unlike those in nonhuman primates, mirror neurons in Homo sapiens allow the copying of actions, even when pantomimed, and also permit unrewarded imitation. This mechanism seems to be part of a frontoparietal network that operates at a sophisticated level in humans, in not being tied to the prevailing situation, and it is directly linked to brain areas mediating theory of mind, which allows the world to be seen from the perspective of others. The mirror/theory-of-mind system is fundamental to copying actions in an informed way, in that it allows a person to see things from the position of the instructor and therefore promotes learning. Importantly, this system is acutely sensitive to socially derived input in that, should the level of input decline, skills will be lost (Heyes 2003, 2010), because such learning depends on associative processes that require sustained intervention to be maintained (Catmur, Walsh, and Heyes 2009). This means that, because the copying of skills as a function of the mirror system is based on associative learning, expertise can rapidly be lost should socioecological circumstances change. Thus, the more one engages visuomotor skills, the easier it becomes to imitate actions in several domains. Accordingly, when there is greater interaction between subgroups, which is more likely with higher population densities, the mirror/theory-of-mind network is more able to be exploited—a process that can be further engaged through the dynamic interaction between the system itself and interacting individuals within the group, thanks to the “ratchet effect.” As most skills are difficult to acquire, not least because of the sophistication that accrues as a result of this effect, when population rates decline or become more dispersed, skills will be lost because of a lack of input on which the mirror/theory-of-mind system can act. This will eventuate whether learning occurs through straightforward observation or is more structured, although the latter will entail more devastating effects because of the level of expertise required. Note that, especially for skills involving visuospatial/motor capacities, that is, procedural abilities, considerable training is needed before an individual is able to acquire the necessary competence. It is thus concluded that the mirror/theory-ofmind system, which is linked to working memory, was already in place before the appearance of H. sapiens and that the ebb and flow of the archaeological record during the Middle to Upper Paleolithic reflects the various ecological conditions that affected behavior as function of this neurocognitive substrate.