Early agricultural pathways: moving outside the ‘core area’ hypothesis in Southwest Asia

Dorian Q. Fuller 2 George Willcox 1 Robin G. Allaby 0 0 School of Life Sciences , Wellesbourne Campus , University of Warwick , Warwickshire CV35 9EF , UK 1 Arch e orient, CNRS, Antenne de Jale` s , Berrias, F-07460 St-Paul-le-Jeune , France 2 Institute of Archaeology, University College London , 31-34 Gordon Square, London WC1H 0PY , UK The origins of agriculture in the Near East has been associated with a 'core area', located in south-eastern Turkey, in which all major crops were brought into domestication within the same local domestication system operated by a single cultural group. Such an origin leads to a scenario of rapid invention of agriculture by a select cultural group and typically monophyletic origins for most crops. Surprisingly, support for a core area has never been directly tested with archaeological evidence. Over the past decade a large amount of new archaeological and genetic evidence has been discovered which brings new light on the origins of agriculture. In this review, this new evidence was brought together in order to evaluate whether a core region of origin is supported. Evidence shows that origins began earlier than previously assumed, and included 'false starts' and dead ends that involved many more species than the typical eight founder crops associated with the core area. The rates at which domestication syndrome traits became fixed were generally slow, rather than rapid, and occurred over a geographically wide range that included the North and South Levant as well as the core area. Finally, a survey of the estimated ages of archaeological sites and the onset of domestication indicates that the domestication process was ongoing in parallel outside of the core area earlier than within it. Overall, evidence suggests a scenario in which crops were domesticated slowly in different locations around the Near East rather than emanating from a core area. - Introduction Agricultural origins is a topic of continuing interest amongst anthropologists and biologists and the better studied Near Eastern area of crop domestications continues to be at the forefront of debates about the process of plant domestications at the dawn of agriculture (Brown et al., 2009; Honne and Heun, 2009; Purugganan and Fuller, 2009; Allaby et al., 2010; Abbo et al., 2010a, b, 2011; Fuller, 2010). In the present paper, the evidence from both genetics and archaeobotany for a single, rapid origin versus that in favour of a mosaic of slower processes is evaluated and it is concluded that these data increasingly support the latter and undermine the concept of a core area (sensu Lev-Yadun et al., 2000). It is well-established that the wild ancestors of a number of major crops, cereals, pulses, and flax, co-occur in Southwest Asia, in a region that has come to be known as the Fertile Crescent, a term coined by the late 19th century archaeologist and orientalist JH Breasted (1906). Through the course of archaeological research and thinking in the 20th century, especially through workers such as Childe (1935) and Braidwood and Howe (1960), this geographical region shifted from being the focus of the earliest civilizations (in Breasteds conception, the western wing extended to Egypt) to being the focus of the development of agriculture which underpinned the civilizations of Egypt, Mesopotamia, and Europe. Botanical research, exemplified The Author [2011]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: by that of Zohary (1969, 1999) and a tradition continued by Abbo et al. (2010a, 2011; Lev-Yadun et al., 2000), served to document the geography and habitats of the closest wild relatives of the crops that originated here and provided the specimens from which genetic work has been able to explore in more detail the interrelationships of existing wild and domesticated populations. Zohary (1996) recognized eight major founder crops, which can be found in cultivation today and in wild form in the region, including einkorn (Triticum monococcum), emmer (Triticum diccocum), barley (Hordeum vulgare), lentil (Lens culinaris), pea (Pisum sativum), chickpea (Cicer arietinum), bitter vetch (Vicia ervilia), and flax (Linum usitatissimum) (Zohary and Hopf, 2000; Abbo et al., 2010a; Table 1). Current scholarly opinions are divided between whether agricultural origins in the Near East occurred by a protracted and diffuse process (Nesbitt, 2004; Willcox, 2005; Fuller, 2007; Brown et al., 2009) or a focused, single process (Zohary, 1999; Bar-Yosef, 2003; Kozlowski and Aurenche, 2005; Abbo et al., 2010a, 2011). In some recent reviews on the origins of agriculture in the Near East (Southwest Asia), Abbo et al. (2010a, 2011) argue that crop domestication occurred just once in the Near East, in a core area (after Lev-Yadun et al., 2000) or golden triangle (Kozlowski and Aurenche, 2005), where the whole package of eight founder crops were brought into cultivation at essentially the same time. From here, cultivation of these species spread, and if the same wild species was brought into cultivation elsewhere it was under the influence of the earlier traditions of cultivation in this core region. Theirs is an argument in which agriculture was a great, and rare, invention by a select cultural group in the Near East, and in a few other regions in the world. Their argument implies a rapid domestication process and a simple monophyletic origin for the founder crops (Zohary, 1999). It emphasizes single genes and single traits as markers of domestications, such as non-shattering in cereals (Peleg et al., 2011) and free germination in legumes (Abbo et al., 2010b), whereas the protracted models explore an adaptive syndrome of domestication traits that evolved during the early era of cultivation. In the present paper, the evidence of genetics, biogeography, and archaeobotany of crop domestication in the Levant region of Southwest Asia which undermines the model of a core area (shown in Fig. 1) and rapid domestication (represented by the recent papers of Abbo et al., 2010a, 2011) will be reviewed succinctly. Multiple lines of evidence across several crops point to plant domestication as a protracted evolutionary process that resulted from unintended, as well as intended, consequences of strategic human subsistence behaviours, local ecologies, and processes of population genetics but was not a conscious revolution (Kislev, 2002; Nesbitt, 2004; Willcox, 2005; Weiss et al., 2006; Fuller, 2007; Allaby et al., 2008, 2010; Brown et al., 2009; Purugganan and Fuller, 2009). Beyond arguing for multi-locus and diffuse domestication processes the core area hypothesis is tested against current evidence. Just over a decade ago, the available genetic evidence could be seen to suggest single origins for most Near Eastern crops (Zohary, 1999; Zohary and Hopf, 2000; Species (wild progenitor) Early archaeological occurrences Lates (...truncated)