Glacial Cycles and Palaeolithic Adaptive Variability on China's Western Loess Plateau

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Introduction

Recently, Hill et al. (2009) argued that the last glacial cycle played a major role in the evolution of modern human behaviour, especially in the emergence of non-kin cooperation, the development of larger groups and the evolution of intensive technologies and subsistence strategies (see also Richerson et al. 2009). The advantages associated with these behaviours, they suggested, explain the trend toward increasing human dominance of global ecologies through the Terminal Pleistocene and Holocene. While certainly true in a temporal sense, the way cultural adaptations evolved in concert with the environmental changes associated with this cycle is anything but clear. While some posit more-or-less direct relationships between environmental productivity and behavioural changes (e.g. Ambrose 1998), several confounding factors cloud the issue, specifically: the increasingly complex picture of hominid biological evolution in Eurasia (e.g. Krause et al. 2010), catastrophic volcanism (Golovanova et al. 2010) and social factors like the effects of risk sensitivity and group size on innovation, learning and long-term cultural transmission (Henrich 2004; Morgan 2009).

Relative to this context, the goals of the research reported here are twofold. The first is to provide a descriptive summary of work conducted since 2002 by our team of Chinese and American researchers on China's Western Loess Plateau (WLP), where we have documented a record of human occupation spanning more than 80 000 years and most of the last glacial cycle. The second is to explore the relationship between major climatic shifts and variability in human technological, subsistence and settlement patterns. The idea here is to generate hypotheses that might identify causal connections between climate change, glacial cycling and the evolution of modern human behaviour in East Asia. This is a region that Norton and Jin (2009: 251) identify as critical to understanding the evolution of modern human behaviour, but which is woefully lacking in synthesis. This exploration begins with an overview of the regional palaeo environment and archaeology during the last glacial cycle, is followed by a summary of survey, excavation and analysis results and concludes with a consideration of the role of climate change in East Asian Palaeolithic cultural evolution.

Late Quaternary climate, environment and archaeology in north-east Asia

The last glacial cycle spans the MIS5 interglacial through the MIS2 stadial (i.e. the Last Glacial Maximum [LGM]), roughly 130 to 18 kya (Table 1). MIS5 is marked by pronounced climatic variability (Feng & Wang 2006), warm-wet phases and a northward advance of temperate forest/steppe biomes. The shift from warmer-wetter MIS5 interglacial biomes to cold, wet glacial conditions during early MIS4 resulted in the expansion of coniferous forests at the expense of deserts across the WLP (Feng et al. 1998), a trend which reversed after ~60 kya with the transition to MIS3. At this time the forests of the WLP gave way to a forest-steppe patchwork, with broadleaf taxa gradually supplanting coniferous ones (Feng et al. 2007). Across East Asia, technology was remarkably conservative from ~50-13 kya, dominated by an expedient core/flake industry using mostly locally-available and abundant raw materials (Ikawa-Smith 1978). Despite what appears to be technological continuity, however, relatively few archaeological sites or human fossils date between ~100-50 kya (Brown 2001), a phenomenon some attribute to regional abandonments associated with the MIS4 stadial (Ambrose 1998).

By the middle of MIS3 (~45 kya), winters were warmer, the summer phase of the East Asian monsoon was stronger, precipitation penetrated deeper inland (Yu et al. 2007) and wetlands developed across the WLP (Feng et al. 2007)--many containing archaeological sites (Ji et al. 2005). Late MIS3 saw a number of important cultural developments associated with what many consider to be the inception of modern human behaviour. …