Jade d'Alpoim Guedes

Early evidence for the use of wheat and barley as staple crops on the margins of the Tibetan Plateau

Significance Adapting agricultural systems to the high-altitude environment of the Tibetan Plateau has long been considered a major challenge for farmers. It has been asserted previously that the ecological characteristics of wheat and barley delayed their spread into East Asia. We argue instead that the ability of these crops to tolerate frost and their low heat requirements facilitated their spread into the high-altitude margins of western China. Following their introduction to this region, these crops rapidly replaced Chinese millets that could not adapt to the cooler temperatures of post-Holocene climatic optimum East Asia. We present data from the eastern Tibetan Plateau demonstrating that wheat and barley rapidly became staple crops shortly after their introduction. We report directly dated evidence from circa 1400 calibrated years (cal) B.C. for the early use of wheat, barley, and flax as staple crops on the borders of the Tibetan Plateau. During recent years, an increasing amount of data from the Tibetan Plateau and its margins shows that a transition from millets to wheat and barley agriculture took place during the second millennium B.C. Using thermal niche modeling, we refute previous assertions that the ecological characteristics of wheat and barley delayed their spread into East Asia. Rather, we demonstrate that the ability of these crops to tolerate frost and their low growing degree-day requirements facilitated their spread into the high-altitude margins of western China. Following their introduction to this region, these crops rapidly replaced Chinese millets and became the staple crops that still characterize agriculture in this area today.

Rethinking the spread of agriculture to the Tibetan Plateau

New data from the Tibetan Plateau allow us to understand how populations dealt with the challenges of moving crops into altitudinally constrained environments. Despite the interest in explaining the timing and the mechanisms via which agricultural products spread to the roof of the world, current models for the spread of agriculture to this region have been simplistic and the presence of crop domesticates is often straightforwardly interpreted as indicating the existence of an agricultural system at the site. This is largely due to a fundamental lack of understanding of where crops could be grown in prehistory on the Plateau. Although it has generally been assumed that moving agriculture into this area was challenging, little work has specifically addressed the constraints imposed on humans as they moved crops into this area. Employing an agro-ecological niche model, I formally model the constraints that were faced by humans as they moved a series of crops into the Tibetan Plateau between the 4th and 1st millennium cal. BC. Based on the results of this analysis, I argue that the end of the climatic optimum meant that millet agriculture was no longer a viable strategy in many parts of the Eastern Himalayas. The arrival of frost tolerant crops in the 2nd millennium BC provided new opportunities in the cooler post climatic optimum world. These models further reveal that sites that have been previously considered as engaged directly in agricultural production may have been more distantly connected to an agricultural lifestyle than previously thought.New data from the Tibetan Plateau allow us to understand how populations dealt with the challenges of moving crops into altitudinally constrained environments. Despite the interest in explaining the timing and the mechanisms via which agricultural products spread to the roof of the world, current models for the spread of agriculture to this region have been simplistic and the presence of crop domesticates is often straightforwardly interpreted as indicating the existence of an agricultural system at the site. This is largely due to a fundamental lack of understanding of where crops could be grown in prehistory on the Plateau. Although it has generally been assumed that moving agriculture into this area was challenging, little work has specifically addressed the constraints imposed on humans as they moved crops into this area. Employing an agro-ecological niche model, I formally model the constraints that were faced by humans as they moved a series of crops into the Tibetan Plateau between the 4th and 1st millennium cal. BC. Based on the results of this analysis, I argue that the end of the climatic optimum meant that millet agriculture was no longer a viable strategy in many parts of the Eastern Himalayas. The arrival of frost tolerant crops in the 2nd millennium BC provided new opportunities in the cooler post climatic optimum world. These models further reveal that sites that have been previously considered as engaged directly in agricultural production may have been more distantly connected to an agricultural lifestyle than previously thought.

Millets, Rice, Social Complexity, and the Spread of Agriculture to the Chengdu Plain and Southwest China

Southwest China played a pivotal role in the spread of agriculture across East and Southeast Asia. Both rice and millet were important in the spread of populations and the expansion of agriculture into this region. Recent finds in the mountainous peripheries of Sichuan Province show that the earliest inhabitants of this region practiced a combination of broomcorn and foxtail millet agriculture (ca 4000–2500 BC). These crops are adapted to high altitude and arid environments, which facilitated their movement across this region and eventually into the Tibetan Plateau. At around 2700 BC, a combined system of rice and foxtail millet agriculture appears suddenly in sites of the Baodun culture on the Chengdu Plain. The use of this double cropping system provided advantages to the inhabitants of this region in both risk reduction and yield. I argue that this had important consequences for spurring population growth, facilitating expansion into new territories and the development of social complexity.Southwest China played a pivotal role in the spread of agriculture across East and Southeast Asia. Both rice and millet were important in the spread of populations and the expansion of agriculture into this region. Recent finds in the mountainous peripheries of Sichuan Province show that the earliest inhabitants of this region practiced a combination of broomcorn and foxtail millet agriculture (ca 4000–2500 BC). These crops are adapted to high altitude and arid environments, which facilitated their movement across this region and eventually into the Tibetan Plateau. At around 2700 BC, a combined system of rice and foxtail millet agriculture appears suddenly in sites of the Baodun culture on the Chengdu Plain. The use of this double cropping system provided advantages to the inhabitants of this region in both risk reduction and yield. I argue that this had important consequences for spurring population growth, facilitating expansion into new territories and the development of social complexity.

Is poverty in our genes? A critique of Ashraf and Galor, "The 'out of Africa' hypothesis, human genetic diversity, and comparative economic development," American Economic Review (Forthcoming)

We present a critique of a paper written by two economists, Quamrul Ashraf and Oded Galor, which is forthcoming in the American Economic Review and which was uncritically highlighted in Science magazine. Their paper claims there is a causal effect of genetic diversity on economic success, positing that too much or too little genetic diversity constrains development. In particular, they argue that “the high degree of diversity among African populations and the low degree of diversity among Native American populations have been a detrimental force in the development of these regions.” We demonstrate that their argument is seriously flawed on both factual and methodological grounds. As economists and other social scientists begin exploring newly available genetic data, it is crucial to remember that nonexperts broadcasting bold claims on the basis of weak data and methods can have profoundly detrimental social and political effects.

Site of Baodun yields earliest evidence for the spread of rice and foxtail millet agriculture to south-west China

The Chengdu plain of south-west China lies outside the main centres of early domestication in the Huanghe and Yangzi valleys, but its importance in Chinese prehistory is demonstrated by the spectacular Sanxingdui bronzes of the second millennium BC and by the number of walled enclosures of the third millennium BC associated with the Baodun culture. The latter illustrate the development of social complexity. Paradoxically, however, these are not the outcome of a long settled agricultural history but appear to be associated with the movement of the first farming communities into this region. Recent excavations at the Baodun type site have recovered plant remains indicating not only the importance of rice cultivation, but also the role played by millet in the economy of these and other sites in south-west China. Rice cultivation in paddy fields was supplemented by millet cultivation in neighbouring uplands. Together they illustrate how farmers moving into this area from the Middle Yangzi adjusted their cultivation practices to adapt to their newly colonised territories.

Twenty-first century approaches to ancient problems: Climate and society

By documenting how humans adapted to changes in their environment that are often much greater than those experienced in the instrumental record, archaeology provides our only deep-time laboratory for highlighting the circumstances under which humans managed or failed to find to adaptive solutions to changing climate, not just over a few generations but over the longue durée. Patterning between climate-mediated environmental change and change in human societies has, however, been murky because of low spatial and temporal resolution in available datasets, and because of failure to model the effects of climate change on local resources important to human societies. In this paper we review recent advances in computational modeling that, in conjunction with improving data, address these limitations. These advances include network analysis, niche and species distribution modeling, and agent-based modeling. These studies demonstrate the utility of deep-time modeling for calibrating our understanding of how climate is influencing societies today and may in the future.

The Impact of Climate on the Spread of Rice to North-Eastern China: A New Look at the Data from Shandong Province

Moving crops outside of their original centers of domestication was sometimes a challenging process. Because of its substantial heat requirements, moving rice agriculture outside of its homelands of domestication was not an easy process for farmers in the past. Using crop niche models, we examine the constraints faced by ancient farmers and foragers as they moved rice to its most northerly extent in Ancient China: Shandong province. Contrary to previous arguments, we find that during the climatic optimum rice could have been grown in the region. Climatic cooling following this date had a clear impact on the distribution of rice, one that may have placed adaptive pressure on rice to develop a temperate phenotype. Following the development of this temperate phenotype, rice agriculture could once again become implanted in select areas of north-eastern China.

Proso millet (Panicum miliaceum L.) and its potential for cultivation in the Pacific Northwest, U.S.: A review

Proso millet (Panicum miliaceum L.) is a warm season grass with a growing season of 60–100 days. It is a highly nutritious cereal grain used for human consumption, bird seed, and/or ethanol production. Unique characteristics, such as drought and heat tolerance, make proso millet a promising alternative cash crop for the Pacific Northwest (PNW) region of the United States. Development of proso millet varieties adapted to dryland farming regions of the PNW could give growers a much-needed option for diversifying their predominantly wheat-based cropping systems. In this review, the agronomic characteristics of proso millet are discussed, with emphasis on growth habits and environmental requirements, place in prevailing crop rotations in the PNW, and nutritional and health benefits. The genetics of proso millet and the genomic resources available for breeding adapted varieties are also discussed. Last, challenges and opportunities of proso millet cultivation in the PNW are explored, including the potential for entering novel and regional markets.

Comment on “Agriculture facilitated permanent human occupation of the Tibetan Plateau after 3600 B.P. ”

Chen et al. (Reports, 16 January 2015, p. 248) argued that early Tibetan agriculturalists pushed the limits of farming up to 4000 meters above sea level. We contend that this argument is incompatible with the growing requirements of barley. It is necessary to clearly define past crop niches to create better models for the complex history of the occupation of the plateau.

A 5,500-Year Model of Changing Crop Niches on the Tibetan Plateau

The timing and mechanics of the spread of agriculture to the Tibetan Plateau—one of the most challenging environmental contexts on earth—is a focus of recent work and debate. Understanding the timing and spread of agriculture is basic to archaeology and history worldwide. Researchers seek evidence for the earliest, furthest, or highest occurrences of diagnostic elements. However, the Tibetan Plateau case illustrates a key flaw in current work: archaeologists have often uncritically interpreted the presence of plant domesticates at archaeological sites as being indicative of local agricultural practice. This assumption neglects the long history of food exchange on the Plateau, as elsewhere in the world, even beyond what were then the limits of agriculture. The cause is a fundamental lack of understanding of where crops could be grown in prehistory. Using a formal model of the agricultural thermal niche between the 5500 BP and the present, we argue that agricultural niches on the Tibetan Plateau were tightly constrained to lower-elevation river valleys throughout time. This pattern is confirmed by analysis of the extent of modern crop production on the Plateau. The challenges deriving from these altitudinal constraints placed on early Tibetans largely explain how and why the Tibetan economy developed in the way that it did.