Human Bioarchaeology of the Transition to Agriculture

Ron Pinhasi, Jay T. Stock, Ron Pinhasi, Jay T. Stock

• Publisher: Wiley
• Year: 2011
• Print ISBN: 9780470747308
• eBook ISBN: 9781119956686
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Human Anatomy & Physiology
• Index: Biological Sciences

A holistic and comprehensive account of the nature of the transition from hunting to farming in prehistory. It addresses for the first time the main bioarchaeological aspects such as changes in mobility, behaviour, diet and population dynamics.

This book is of major interest to the relevant audience since it offers for the first time a global perspective on the bioarchaeology of the transition to agriculture. It includes contributions from world-class researchers, with a particular emphasis on advances in methods (e.g. ancient DNA of pathogens, stable isotope analysis, etc.).

The book specifically addresses the following aspects associated with the transition to agriculture in various world regions:

• Changes in adult and subadult stature and subadult growth profiles
• Diachronic trends in the analysis of functional morphological structures (craniofacial, vault, lower limbs, etc.) and whether these are associated with change in overall sex-specific morphological variability
• Changes in mobility
• Changes in behaviour which can be reconstructed from the study of the skeletal record. These include changes in activity patterns, sexual dimorphism, evidence of inter-personal trauma, and the like.
• Population dynamics and microevolution by examining intra and inter population variations in dental and cranial metric traits, as well as archaeogenetic studies of ancient DNA (e.g. mtDNA markers).

1

Introduction

Changing Paradigms in Our Understanding of the Transition to Agriculture: Human Bioarchaeology, Behaviour and Adaptation

Jay T. Stock¹and Ron Pinhasi²

¹Leverhulme Centre for Human Evolutionary Studies, Department of Biological Anthropology, University of Cambridge, Cambridge, UK

²Department of Archaeology, University College Cork, Cork, Ireland

The evolution and history of our species is often considered as a series of major transitions and processes of evolution, which collectively ‘make’ us human (Klein, 2009). In this context, it is easy to view modern human origins and dispersals as the end of a long process of cultural and biological evolution, and the point of demarcation between the end of biological evolution and the period when socio-cultural evolution and diversity becomes the hallmark of our species (Dyson, 1997). The ‘Neolithic Revolution’, a term coined by Gordon Childe, is the central component in this perspective, referring to the transition from hunting and gathering to agricultural subsistence in the Holocene. It has been seen as perhaps the single most significant social, cultural and biological transition since the origin of our species, marking the development of human control over the reproduction and evolution of plants and animals (Childe, 1936). A natural conclusion of this perspective suggests that the Neolithic marks the period where humans shifted from being subject to changes in the natural environment, to become the agents of environmental change in which the natural world is modified to suit human needs.

The transition to agriculture is often viewed as the beginning of a series of significant changes in human social organization, on the basis of the rise of food production and the storage of food surpluses. These are interpreted as leading to property ownership, social hierarchy, task specialization and runaway technological evolution, which is fuelled by a surplus of food (Diamond, 1997). In this context, agriculture can also be viewed as a form of niche colonization, which allows populations to enter a new adaptive niche within the same environment as hunter-gatherers. When this is combined with food surpluses, it results in reduced interbirth intervals; increased birth stacking associated with alloparenting, and increased fertility (Wells and Stock, 2007). It has long been speculated whether demographic shifts amongst hunter-gatherer societies stimulated this cultural change, because greater numbers could not be sustained on the basis of hunter-gatherer subsistence (Boserup, 1965; Cohen, 1977), and it has recently been argued that consensus falls on this ‘push’ model (Cohen, 2009). Regardless of whether demography was a causal factor in development of agriculture in different regions, it is apparent that major demographic change was a primary consequence of the transition to agriculture (Bocquet-Appel and Bar-Yosef, 2008). Whether population size was an important catalyst for, or a consequence of, the transition to agriculture, the positive feedback between demography and culture certainly underpinned subsequent urbanization and state formation. Agriculture remains the primary means of production underpinning the global population and economy today.

1.1 THE ORIGINS OF AGRICULTURE

The earliest evidence for the transition to agriculture occurs in the Levant, a region of the Eastern Mediterranean, including Syria, Lebanon, Israel, Palestine and Jordan. The late Epipalaeolithic ‘Natufian’ (about 14 500–11 600 calBP) period in this region is seen as reflecting a cultural precursor of the subsequent pre-pottery Neolithic, due to the extensive exploitation of wild grains and the use of groundstone, stone architecture and a variety of organized site structures, art and evidence for symbolic behaviour (Bar-Yosef, 1998; Belfer-Cohen and Bar-Yosef, 2000; Byrd, 2005; Goring-Morris, Hovers and Belfer-Cohen, 2009). These cultural characteristics are often interpreted as the earliest archaeological signature of the transition towards agriculture, with the final impetus for the Neolithic being the dramatic environmental cooling associated with the Younger Dryas climatic event (Bar-Yosef and Belfer-Cohen, 2002). The earliest evidence for plant cultivation comes from the site of Abu Hureyra at about 13 000 BP, and appears to be associated with a decline in wild plants associated with the Younger Dryas (Hillman et al, 2001). The subsequent Pre-pottery Neolithic A period shows the first evidence for larger permanent human settlements with architecture, and demonstrates the first evidence for intensive use of grains, as evidenced by the 11 kya granaries at ‘Dhra in Jordan (Kuijt and Finlayson, 2009). These PPNA villages represent the earliest expression of the Neolithic, but they also reflect an extension of trends in social complexity, longer-term site use, and extensive use of wild grains which occurred earlier in the Natufian (Byrd, 2005). While these late Pleistocene and early Holocene cultures in the Near East and Anatolia reflect the earliest transition to farming, it is now well established that agriculture originated independently in different regions of the world at different times throughout the first half of the Holocene (Smith, 1998; Diamond, 2002; Bellwood, 2005). Other regions of primary plant domestication include southern China, Ethiopia, New Guinea, and three different regions of the New World: Southeast North America, Meso-America and western South America (Bellwood, 2005), and there were also a number of independent centres of animal domestication (Diamond, 2002).

What explains the development of agriculture in different parts of the world remains an open question; however, it has been argued that there were a number of constraints on the domestication of plants and animals prior to the Holocene, including climate and social organization (Richerson, Boyd and Bettinger, 2001; Bettinger, Richerson and Boyd, 2009). Regardless of these issues, it is clear that the global dominance of agricultural subsistence occurred through a combination of regional innovation with locally domesticable plant and animal species, demographic expansion and cultural diffusion (Bellwood, 2005; Pinhasi, Fort and Ammerman, 2005). The result of this transition is that agriculture is the dominant mode of subsistence today, which supports the large global human population and the socio-economic and technological systems of our species in the modern world.

1.2 THE CONSEQUENCES OF AGRICULTURE

A considerable emphasis of research has been placed on understanding the impact of the adoption of agricultural subsistence on health. This is based on the premise that a shift from diverse diets based on hunting and gathering towards dependence on one or a few highly productive domesticated plants, with a diet based predominantly on complex carbohydrates, can lead to a number of negative health outcomes, including nutritional deficiencies and dental caries. In addition, increasing sedentism associated with permanent or semi-permanent villages, and living in close proximity to domestic animals, leads to poor sanitation and an increased prevalence of zoonotic disease. Palaeopathologial studies have provided a considerable body of evidence that the origins of agriculture often had a negative impact on human health (Cohen and Armelagos, 1984; Cohen, 1989). The palaeopathological paradigm has dominated most research on the impact of agriculture in recent decades; however, it presents a paradox: if agriculture clearly underpins the dramatic demographic expansion and success of our species in the Holocene, how do we explain patterns of pathology? Is there a trade-off between reproductive capacity and health? In this context, we need to ask how the impact of agriculture varies through time and space, and under what cultural conditions it varies.

Recent research is beginning to investigate these questions. A study of linear enamel hypoplasia (LEH), bands of poor quality dental enamel that form during periods of childhood illness or malnutrition, has demonstrated a dramatic increase in the frequency of LEH between the late Palaeolithic and Neolithic of Egypt (Starling and Stock, 2007). While this would be expected based upon models of nutrition and hygiene with the transition to agriculture, the study also showed a gradual recovery in the frequency of LEH with the formation of the Egyptian state, showing that the negative health consequences of agriculture were short-term, and mediated by cultural factors over several millennia. Recent studies investigating health and subsistence transitions across a range of populations have demonstrated a greater diversity of evidence than previously known (Cohen and Crane-Kramer, 2007). These studies demonstrate that there is no simple relationship between subsistence change and health and, while there is still evidence for a decline in health indicators amongst many populations, the emerging picture is more regionally specific and diverse than previously thought.

While research has predominantly focused on the impact of agriculture on human health (Cohen, 1989) and demography (Bocquet-Appel and Bar-Yosef, 2008), there has also been study of the impact of agriculture on other aspects of human biology. A portion of this work, primarily on human remains from North America, has focused on elucidating behavioural correlates of subsistence transitions (Larsen, 1995). This area of research was amongst the earliest to begin to show evidence for regional diversity of human biological change with the transition to agriculture (Bridges, 1989; Ruff, 1999, 2008). Another area of enquiry has investigated the idea of ‘human domestication’, that human populations underwent similar morphological (Leach, 2003) and behavioural changes (Wilson, 1991) as other species, following the transition to agriculture and the process of animal domestication. These approaches suggest a continuing feedback between cultural and human biological change (Durham, 1991). A frequently cited example of biological change associated with the origins of agriculture is dental and mandibular size reduction; however, it remains unknown whether this represents genetic evolution, a relaxation of directional selective pressures, or biological plasticity in response to changes in biomechanics associated with food preparation and dietary homogenization (Pinhasi, Shaw and Eshed, 2008).

1.3 AN ONGOING REVOLUTION’ IN OUR UNDERSTANDING OF THE NEOLITHIC

The above discussion provides a brief, general and conservative picture of the origins of agriculture. A recent review of the issue of agricultural origins from a variety of perspectives, published as a special issue of Current Anthropology, generally supports these interpretations; namely that agriculture was a consequence of increasing population pressure, competition for resources and globally favourable climatic conditions, and it resulted in a general deterioration of health amongst agricultural populations (Cohen, 2009). However, a common theme in the commentary accompanying this issue is that these interpretations represent a broad-scale overview but do not explain regional and temporal variation that is apparent in the archaeological record (Denham, 2009; Belfer-Cohen and Goring-Morris, 2009; Zeder and Smith, 2009). On a surface level we could dismiss these disparities as inevitable conflict between the resolution of data found in specific archaeological contexts and the sort of generalizations that are necessary for understanding global trends. However, it begs the question, to what extent are broad-scale and global trends relevant to regional expressions of Holocene subsistence transitions? To what extent is regional variation important in understanding the ‘big picture’ of the causes and consequences of agriculture? If regional and temporal variation is so significant, can we even make such generalizations?

In recent years, simultaneous developments in our understanding of long-term trends in the archaeology of human populations, human genetic diversity, and animal and plant evolution, have begun to dramatically change our views of the transition to agriculture. The Late Pleistocene and Holocene archaeological record from the Levant presents amongst the most clear archaeological evidence for long-term cultural change associated with the transition to agriculture; however, recent research has demonstrated that the cultural and biological change associated with this transition is more complex than previously thought. In particular, there is evidence that the cultural characteristics of the Neolithic develop over a considerable span of time (Twiss, 2007) from precursors found in the Natufian (Belfer-Cohen and Bar-Yosef, 2000). However, recent excavations suggest that many of the characteristic features of the Natufian period developed gradually over a long period of time in the Late Pleistocene (Maher, 2007; Nadel and Hershkovitz, 1991; Belfer-Cohen and Goring-Morris, 2009). Collectively, the emerging evidence from the Levant suggests that the origins of agriculture did not occur as a rapid Neolithic revolution per se, but as a complex and long-term process of social change in the relationship between human behaviour and the natural environment. This suggests that investigation of subtle cultural, behavioural and dietary change amongst hunter-gatherers, pastoralists and early agricultural populations should be considered on a fine scale, with increased temporal and spatial resolution.

This ‘revolution’ in our understanding of the Neolithic is not restricted to issues of cultural change in the Levant, as there is clear evidence for social complexity and long-term behavioural change in other regions (Denham, 2009; Zeder and Smith, 2009). A major factor underpinning the longer temporal span of the process of domestication maybe the evolution of plants. Recent archaeobotanical research has moved away from simple identification of plant remains at archaeological sites, to examine the evolution of the plants themselves (Fuller and Allaby, 2009). This research demonstrates that the process of plant domestication occurs over a longer temporal span, and occurs across plant taxa and in different centres of domestication (Fuller and Allaby, 2009; Fuller, Allaby and Stevens, 2010). This not only has implications for the timing of cultural change associated with the agricultural transition, but also the expression of culture and habitual behaviour associated with subsistence activity. The evolution of domestic plants from wild progenitors involves a narrowing of the period of ripening of seeds from several months to several weeks, presenting what has been called a ‘labour bottleneck’ (Fuller, Allaby and Stevens, 2010). Furthermore, wild grasses generally disperse seeds by the presence of an ‘abscission scar’, which is often lost in the process of domestication. As a result, domestic plants often require human activity, in the form of threshing and winnowing, to separate and disperse seeds. This has been called a ‘labour trap’ of domestication (Fuller, Allaby and Stevens, 2010) associated with the transition to agricultural food sources. While this does not necessarily mean that agricultural subsistence is more labour intensive than other subsistence strategies in all circumstances, it suggests that the transition to agriculture is behaviourally complex and likely fuelled technological innovation throughout much of the Holocene.

A further area where there has been major change in our understanding of the transition to agriculture has been in human genetics. Until very recently, many assumed that human evolution is at a standstill in the modern world, due largely to human control over the natural environment (Dyson, 1997). This perspective was based largely on the assumption the technological developments following the origins of agriculture led to rapid technological evolution and increasingly successful ‘niche construction’, where humans successfully modify the natural environment, and thus remove pressures of natural selection. This assumption was never justified by the niche construction model, and it is increasingly clear that modification of the environment not only buffers environmental stress but actually exerts new selective pressures on the genome (Laland and Brown, 2006; Stock, 2008). Selective pressure on the genome resulting from stresses associated with the transition to agriculture has been detected through evidence for selection in a number of genes, related to malarial resistance (Tishkoff et al, 2001), lactase persistence (Burger et al, 2007; Tishkoff et al, 2007) and amylase gene copy variation (Perry et al, 2007). The latter two cases appear to be the results of direct selection of particular genes in response to dietary stress associated with domestication of animals and plants. These cases relate to the use of milk as a fallback food amongst Neolithic populations, and the shift towards higher components of dietary starch, which may have driven selection for higher AMY1 copy numbers to aid starch hydrolysis, respectively. Recent research has dramatically extended our understanding of recent human evolution, on the basis of new methods for the detection of signatures of natural selection within the genome (Sabeti et al, 2007). Further genetic analysis has identified greater genetic heterogeneity amongst modern humans than would be otherwise expected, leading to the speculation that the pace of human evolution has speeded up in recent prehistory (Hawks et al, 2007). It will take a considerable amount of research to sort out what specifically this genetic diversity means in terms of evolution, drift and demographic factors; but it does seem clear that recent cultura changes are a major force driving evolution within our species (Laland, Odling-Smee and Myles, 2010).

The previous discussion has presented evidence that we are in the midst of a major change in our interpretation of the origin of agriculture. This includes several fundamental shifts in perspective:

1. that socio-cultural and dietary change likely occurred over a considerable range of time, involving change within socially complex hunter-gatherers, pastoralists and agriculturalists;

2. that the process of the transition to agricultural subsistence was regionally specific, and we cannot expect to find universal trends and characteristics of this transition;

3. that evolution of plants during the process of domestication posed both constraints upon the process of cultural change, and its own influence on behavioural adaptation through the ‘labour trap’ associated with winnowing and threshing; and

4. that cultural change associated with the transition to agriculture exerted its new selective pressures on human populations, driving continuing human evolution within the Holocene.

1.4 HUMAN BIOARCHAEOLOGY OF THE TRANSITION TO AGRICULTURE

Human remains comprise the primary evidence for human biology with the transition to agriculture. In this volume, we provide a synthesis of the bioarchaeological evidence for changes in mobility, behaviour, diet, growth, population dynamics and evolution associated with the transition to agriculture. We assemble the work of a number of researchers who have been independently tackling questions relating to human biology associated with major dietary transitions of the Late Pleistocene and early Holocene. Given recent and major shifts in our understanding of the complexity of the transition to agriculture in different parts of the world, it would be impossible for a volume of this sort to be exhaustive, or to provide a comprehensive review of all evidence. Instead we aim to provide a synthesis of current approaches to understanding the biological correlates and consequences of major subsistence transitions in the Late Pleistocene and Holocene, in the hope that these studies will stimulate further research.

The contributions presented here are innovative in several ways: they emphasize the complexity of social and cultural change, and often employ multidisciplinary approaches to understanding the context and consequences of the agricultural transition. Major themes in the book include:

• the direct evidence for dietary change through the use of stable isotope analyses; variation in growth associated with dietary and cultural change;
• skeletal biomechanics and evidence for variation in habitual behaviour; craniofacial morphology, population history and adaptation; and
• evidence for genetic adaptation relating to Holocene cultural change.

In addition, several chapters build upon the dismantling of the traditional hunter-gatherer/ agriculturalist dichotomy, by investigating subtle variation in human biology amongst hunter-gatherers, pastoralists, and early cultivators and agriculturalists. Other studies take ...

Table of contents

• Cover
• Title
• Copyright
• Foreword
• List of Contributors
• 1: Introduction
• SECTION A: Subsistence Transitions
• SECTION B: Growth and Body Size Variation
• SECTION C: Biomechanics and Indicators of Habitual Activity
• SECTION D: Archaeogenetics, Palaeodemography, Cranial and Dental Morphology
• Color Plates
• Index