From single neurons to social brains

The manufacture of stone tools is an integral part of the human evolutionary trajectory. However, very little research is directed towards the social and cognitive context of the process of manufacture. This article aims to redress this balance by using insights from contemporary neuroscience. Addressing successively more inclusive levels of analysis, we will argue that the relevant unit of analysis when examining the interface between archaeology and neuroscience is not the individual neuron, nor even necessarily the individual brain, but instead the socio-cognitive context in which brains develop and tools are manufactured and used. This context is inextricably linked to the development of unique ontogenetic scheduling, as evidenced by the fossil record of evolving hominin lineages

Rethinking Phylogeny and Ontogeny in Hominin Brain Evolution

Theories of hominin and human cognitive evolution have traditionally focused on the phylogeny of the human brain, and on comparisons of human and primate brains in relation to social or ecological variables. Far less attention has been paid to ontogenetic processes, despite the recognition that experience has a profound influence on adult cognition. In this paper we discuss the interplay between phylogeny and ontogeny by examining relationships between human brain size, developmental scheduling and cognition. The correlates of large brains include not only altered subsistence and life-history strategies to meet associated energetic costs, but also on macro- and micro-scale structural adaptations required to meet increased processing costs. This means that larger brains are of necessity more highly interconnected brains, with higher degrees of folding of the neocortex (gyrification) and higher ratios of myelinated connections between neurons (white matter) to neurons themselves (grey matter). Here we argue that the combination of these evolutionary trends underpins the complexity of human behaviour, as the neural circuits involved in cognitive mechanisms such as the mirror neuron system (the system governing motor emulation and imitation) and theory of mind (fundamental in social cognition) mature only slowly, and require considerable socially-scaffolded experience to develop to their full potential. These abilities are likely to be fundamental in characteristically human behaviours such as the cultural transmission of complex forms of tool manufacture and use, attested to in the archaeological record. Their elaborated modern human forms, we argue, are possible only in the context of the evolution of relatively slower trajectories of brain growth and hence longer periods during which the growing brain can be influenced by experience among modern humans relative to other primates. Here we review some of the differences in ontogenetic brain development between humans and other primates, and compare the rates and trajectories of neural development between ourselves and our closest living relatives the chimpanzees to suggest that the human pattern of expanded periods of growth coupled with slower trajectories of neural development is likely to have been of huge significance during hominin evolution. In addition, we discuss fossil and archaeological proxies which might allow the reconstruction of evolutionary patterns of development, suggesting that it is only post-Homo erectus and specifically among Homo heidelbergensis and Homo neanderthalensis populations that developmental patterns approximate those of modern humans, arguing for a similar – but not identical – role for socially-scaffolded learning of complex technical skills as among modern groups in these species

Metaphor and Materiality in Early Prehistory

In this paper we argue for a relational perspective based on metaphorical rather than semiotic understandings of human and hominin1 material culture. The corporeality of material culture and thus its role as solid metaphors for a shared experience of embodiment precedes language in the archaeological record. While arguments continue as to both the cognitive abilities that underpin symbolism and the necessary and sufficient evidence for the identification of symbolic material culture in the archaeological record, a symbolic approach will inevitably restrict the available data to sapiens or even to literate societies. However, a focus on material culture as material metaphor allows the consideration of the ways in which even the very earliest archaeological record reflects hominins’ embodied, distributed relationships with heterogeneous forms of agent, as will be demonstrated by two case studies

Palaeolithic Social Networks and Behavioural Modernity

In this chapter, we discuss some of the challenges researchers face when using formal analysis methods to study Palaeolithic social networks. We also present alternative and complementary methods that can mitigate those challenges; in particular, we argue that agent-based models are useful tools to test formal methods and explore network questions that cannot be answered solely from the archaeological record. We use such a model to show how different social behaviours are reflected in material networks, and to evaluate the accuracy of a popular method to reconstruct Palaeolithic networks. Finally, we identify a number of fruitful areas that could be targeted by Palaeolithic network analysts, as well as questions for which social network analysis techniques may be particularly well suited

Human perception of symmetry, raw material and size of Palaeolithic handaxes.

It has often been assumed that handaxes were crafted and used primarily by adult males (Hawkes et al. 1997; Kohn & Mithen 1999; Niekus et al. 2012). However, there is no clear scientific or ethnographic evidence to support this. This study aimed to assess modern perceptions of essential morphological traits, including symmetry, raw material and size of handaxes, with a view to ascertaining whether differences exist between males and females in different age groups in their perception of bifaces. A statistical analysis was performed on data gathered through questioning more than 300 individuals, including males and females, adults and subadults (divided into juveniles and children). The study showed that most people prefer symmetrical to asymmetrical handaxes. In particular, females demonstrated a statistically significant preference for symmetrical handaxes. Juveniles and children were significantly more attracted towards symmetrical bifaces than adults, and adult females prefer smaller tools. These results suggest new avenues for research into Palaeolithic tool manufacture and use