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FAO guidelines on water requirements for plant growth in the absence of irrigation, stipulate that cultivation is not viable in areas with less than 450mm of annual rainfall. Indeed, in all maps of agricultural land use, most hyper-arid, arid, and semi-arid drylands are considered unproductive. Yet, modern societies in arid and semi-arid drylands still practice rainfed cultivation under regimes of much lower annual rainfall. This paper presents the results of ethnographic and cross-cultural investigations in the cultivation of Pearl millet, Finger millet and Sorghum, with a global perspective. We use published ethnographic material and novel data collected on the field to build and test models that display the interaction of ecological and geographic variables in explaining agricultural practices. The aim of this research is to show how rainfed agriculture is practised much more often, and in much more suitable areas, than normally reported. This holds the potential for the understanding of how these practices can play a pivotal role for long-term resilience and future sustainability of agricultural systems in drylands.

Taxonomical results: anatomical descriptions and ecological features. Taxonomic classifications were proposed by following Höhn and Neumann (2018) methodology for charcoal identification in species-rich environments. Descriptions of the wood anatomy are accompanied by a list of the main diagnostic characters of each charcoal type, a discussion of each identification and photos of the transverse (TS), tangential longitudinal (TLS) and radial longitudinal (RLS) sections, as well as brief summaries of the ecological distributions and economic features of the taxa in each case.The description of charcoal types follows the standard terminology of the International Association of Wood Anatomists (IAWA) (Wheeler et al. 1989;Ritcher et al. 2004) with minor adaptations for characters not listed by IAWA (e.g. intervessel pits coalescent). Note that not all IAWA characters could be evaluated as some are usually difficult to identify in archaeological charcoal (e.g. length of parenchyma strands). The only quantitative feature included is mean diameter of vessel lumina, which was calculated by measuring a minimum of 10 vessels in 5 different charcoal fragments when possible. Microscopic photographs were taken using the Olympus Stream Basic commercial software and a Olympus BX51 reflected light microscope -available at the laboratory of Environmental Archaeological of Universitat Pompeu Fabra (UPF) -with incident light and magnifications 50x, 100x, 400x and 1000x, which are indicated in each photograph by the scales -200 µm, 100 µm, 50 µm and 20 µm respectively . The allocation to northern Ethiopian taxa is done in relation to available wood and charcoal reference materials from Ethiopia at the Muséum National d'Histoire Naturelle (MNHN) deposits, but also using pre-existing literature and collections from other areas of the world since the available reference samples of Ethiopian taxa are still very limited. As a general rule, the naming of the different taxa follows Friis et al. (2010), who does not mention authorship. However, authorship is included for reference collection samples when available, as well as when quoting botanical synonyms. Botanical synonyms accepted by the International Plant Names Index database (IPNI 2020) are considered to refer to the same taxa when comparing their wood anatomies (e.g. Dodonaea angustifolia, and D. viscosa, see below). Vernacular names in Tigrinya (November et al. 2002, Bekele-Tessema 2007 are transcribed without phonetic characters following the example of Bekele-Tesemma (2007; but see November et al. 2002: 2). The ecological distributions of the species related to each charcoal type are assigned according to Friis et al. (2010) classification into the following vegetational units: i) Desert and semi-desert scrubland (DSS); ii) Acacia-Commiphora woodland and bushland proper (ACB); iii) Acacia wooded grassland of the Rift Valley (ACB/RV); iv) Combretum-Terminalia woodland and wooded grassland (CTW); v) Afromontane woodlands, wooded grasslands and grasslands (DAF/WG); vi) Undifferentia...

Numerous and extensive ‘Stone Walled Sites’ have been identified in southern African Iron Age landscapes. Appearing from around 1200 CE, and showing considerable variability in size and form, these settlements are named after the dry-stone wall structures that characterize them. Stone Walled Sites were occupied by various Bantu-speaking agropastoral communities. In this paper we test the use of pXRF (portable X-ray fluorescence analysis) to generate a ‘supplementary’ archaeological record where evident stratigraphy is lacking, survey conditions may be uneven, and excavations limited, due to the overall site size. We propose herein the application of portable X-ray fluorescence analysis (pXRF) coupled with multivariate exploratory analysis and geostatistical modelling at Seoke, a southern African SWS of historical age (18th century CE). The aim of the paper is twofold: to explore the potential of the application of a low cost, quick, and minimally invasive technique to detect chemical markers in anthropogenic sediments from a Stone Walled Site, and to propose a way to analyse the results in order to improve our understanding of the use of space at non-generalized scales in such sites.

The earliest evidence of agriculture in the Horn of Africa dates to the Pre-Aksumite period (ca. 1600 BCE). Domesticated C 3 cereals are considered to have been introduced from the Near East, whereas the origin (local or not) and time of domestication of various African C 4 species such as sorghum, finger millet, or t’ef remain unknown. In this paper, we present the results of the analysis of microbotanical residues (starch and phytoliths) from grinding stones recovered from two archaeological sites in northeastern Tigrai (Ethiopia), namely Mezber and Ona Adi. Together, both sites cover a time period that encompasses the earliest evidence of agriculture in the region (ca. 1600 BCE) to the fall of the Kingdom of Aksum (ca. 700 CE). Our data indicate that these communities featured complex mixed economies which included the consumption of both domestic and wild plant products since the Initial Pre-Aksumite Phase (ca. 1600 to 900 BCE), including C 3 crops and legumes, but also C 4 cereals and geophytes. These new data expand the record of C 4 plant use in the Horn of Africa to over 1,000 y. It also represents the first evidence for the consumption of starchy products in the region. These results have parallels in the wider northeastern African region where complex food systems have been documented. Altogether, our data represent a significant challenge to our current knowledge of Pre-Aksumite and Aksumite economies, forcing us to rethink the way we define these cultural horizons.

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Finger millet, pearl millet and sorghum are amongst the most important drought-tolerant crops worldwide. They constitute primary staple crops in drylands, where their production is known to date back over 5000 years ago. Compared to other crops, millets and sorghum have received less attention until very recently, and their production has been progressively reduced in the last 50 years. Here, we present new models that focus on the ecological factors driving finger millet, pearl millet and sorghum traditional cultivation, with a global perspective. The interaction between environment and traditional agrosystems was investigated by Redundancy Analysis of published literature and tested against novel ethnographic data. Contrary to earlier beliefs, our models show that the total annual precipitation is not the most determinant factor in shaping millet and sorghum agriculture. Instead, our results point to the importance of other variables such as the duration of the plant growing cycle, soil water-holding capacity or soil nutrient availability. This highlights the potential of finger millet, pearl millet and sorghum traditional cultivation practices as a response to recent increase of aridity levels worldwide. Ultimately, these practices can play a pivotal role for resilience and sustainability of dryland agriculture.

Identifying anthropogenic features at Seoke (Botswana) using pXRF: Expanding the record of southern African Stone Walled Sites. PLoS ONE 16(5): e0250776.