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Functional traits differ between cereal crop progenitors and other wild grasses gathered in the Neolithic fertile crescent.

ABSTRACT: The reasons why some plant species were selected as crops and others were abandoned during the Neolithic emergence of agriculture are poorly understood. We tested the hypothesis that the traits of Fertile Crescent crop progenitors were advantageous in the fertile, disturbed habitats surrounding early settlements and in cultivated fields. We screened functional traits related to competition and disturbance in a group of grass species that were increasingly exploited by early plant gatherers, and that were later domesticated (crop progenitors); and in a set of grass species for which there is archaeological evidence of gathering, but which were never domesticated (wild species). We hypothesised that crop progenitors would have greater seed mass, growth rate, height and yield than wild species, as these traits are indicative of greater competitive ability, and that crop progenitors would be more resilient to defoliation. Our results show that crop progenitors have larger seed mass than wild species, germinate faster and have greater seedling size. Increased seed size is weakly but positively correlated with a higher growth rate, which is primarily driven by greater biomass assimilation per unit leaf area. Crop progenitors also tend to have a taller stature, greater grain yield and higher resilience to defoliation. Collectively, the data are consistent with the hypothesis that adaptations to competition and disturbance gave crop progenitors a selective advantage in the areas surrounding early human settlements and in cultivated environments, leading to their adoption as crops through processes of unconscious selection.

SUBMITTER: Cunniff J

PROVIDER: S-EPMC3905035 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Functional traits differ between cereal crop progenitors and other wild grasses gathered in the Neolithic fertile crescent.

Cunniff Jennifer J Wilkinson Sarah S Charles Michael M Jones Glynis G Rees Mark M Osborne Colin P CP

PloS one 20140128 1

The reasons why some plant species were selected as crops and others were abandoned during the Neolithic emergence of agriculture are poorly understood. We tested the hypothesis that the traits of Fertile Crescent crop progenitors were advantageous in the fertile, disturbed habitats surrounding early settlements and in cultivated fields. We screened functional traits related to competition and disturbance in a group of grass species that were increasingly exploited by early plant gatherers, and ...[more]

PMID: 24489941

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Project description:The domestication of crops in the Fertile Crescent began approximately 10,000 years ago indicating a change from a hunter-gatherer lifestyle to a sedentary, agriculture-based existence. The exploitation of wild plants changed during this transition, such that a small number of crops were domesticated from the broader range of species gathered from the wild. However, the reasons for this change are unclear.Previous studies have shown unexpectedly that crop progenitors are not consistently higher yielding than related wild grass species, when growing without competition. In this study, we replicate more closely natural competition within wild stands, using two greenhouse experiments to investigate whether cereal progenitors exhibit a greater seed yield per unit area than related wild species that were not domesticated.Stands of cereal progenitors do not provide a greater total seed yield per unit ground area than related wild species, but these crop progenitors do have greater reproductive efficiency than closely related wild species, with nearly twice the harvest index (the ratio of harvested seeds to total shoot dry mass).These differences arise because the progenitors have greater seed yield per tiller than closely related wild species, due to larger individual seed size but no reduction in seed number per tiller. The harvest characteristics of cereal progenitors may have made them a more attractive prospect than closely related wild species for the early cultivators who first planted these species, or could suggest an ecological filtering mechanism. Synthesis. Overall, we show that the maintenance of a high harvest index under competition, the packaging of seed in large tillers, and large seeds, consistently distinguish crop progenitors from closely related wild grass species. However, the archaeological significance of these findings remains unclear, since a number of more distantly related species, including wild oats, have an equally high or higher harvest index and yield than some of the progenitor species. Domestication of the earliest cereal crops from the pool of wild species available cannot therefore be explained solely by species differences in yield and harvest characteristics, and must also consider other plant traits.

Project description:The origins of agriculture, 10 000 years ago, led to profound changes in the biology of plants exploited as grain crops, through the process of domestication. This special case of evolution under cultivation led to domesticated cereals and pulses requiring humans for their dispersal, but the accompanying mechanisms causing higher productivity in these plants remain unknown. The classical view of crop domestication is narrow, focusing on reproductive and seed traits including the dispersal, dormancy and size of seeds, without considering whole-plant characteristics. However, the effects of initial domestication events can be inferred from consistent differences between traditional landraces and their wild progenitors.We studied how domestication increased the yields of Fertile Crescent cereals and pulses using a greenhouse experiment to compare landraces with wild progenitors. We grew eight crops: barley, einkorn and emmer wheat, oat, rye, chickpea, lentil and pea. In each case, comparison of multiple landraces with their wild progenitors enabled us to quantify the effects of domestication rather than subsequent crop diversification. To reveal the mechanisms underpinning domestication-linked yield increases, we measured traits beyond those classically associated with domestication, including the rate and duration of growth, reproductive allocation, plant size and also seed mass and number.Cereal and pulse crops had on average 50% higher yields than their wild progenitors, resulting from a 40% greater final plant size, 90% greater individual seed mass and 38% less chaff or pod material, although this varied between species. Cereal crops also had a higher seed number per spike compared with their wild ancestors. However, there were no differences in growth rate, total seed number, proportion of reproductive biomass or the duration of growth.The domestication of Fertile Crescent crops resulted in larger seed size leading to a larger plant size, and also a reduction in chaff, with no decrease in seed number per individual, which proved a powerful package of traits for increasing yield. We propose that the important steps in the domestication process should be reconsidered, and the domestication syndrome broadened to include a wider range of traits.

Project description:We analyze the processing of cereals and its role at Early Neolithic Göbekli Tepe, southeastern Anatolia (10th / 9th millennium BC), a site that has aroused much debate in archaeological discourse. To date, only zooarchaeological evidence has been discussed in regard to the subsistence of its builders. Göbekli Tepe consists of monumental round to oval buildings, erected in an earlier phase, and smaller rectangular buildings, built around them in a partially contemporaneous and later phase. The monumental buildings are best known as they were in the focus of research. They are around 20 m in diameter and have stone pillars that are up to 5.5 m high and often richly decorated. The rectangular buildings are smaller and-in some cases-have up to 2 m high, mostly undecorated, pillars. Especially striking is the number of tools related to food processing, including grinding slabs/bowls, handstones, pestles, and mortars, which have not been studied before. We analyzed more than 7000 artifacts for the present contribution. The high frequency of artifacts is unusual for contemporary sites in the region. Using an integrated approach of formal, experimental, and macro- / microscopical use-wear analyses we show that Neolithic people at Göbekli Tepe have produced standardized and efficient grinding tools, most of which have been used for the processing of cereals. Additional phytolith analysis confirms the massive presence of cereals at the site, filling the gap left by the weakly preserved charred macro-rests. The organization of work and food supply has always been a central question of research into Göbekli Tepe, as the construction and maintenance of the monumental architecture would have necessitated a considerable work force. Contextual analyses of the distribution of the elements of the grinding kit on site highlight a clear link between plant food preparation and the rectangular buildings and indicate clear delimitations of working areas for food production on the terraces the structures lie on, surrounding the circular buildings. There is evidence for extensive plant food processing and archaeozoological data hint at large-scale hunting of gazelle between midsummer and autumn. As no large storage facilities have been identified, we argue for a production of food for immediate use and interpret these seasonal peaks in activity at the site as evidence for the organization of large work feasts.

Dataset Information

Functional traits differ between cereal crop progenitors and other wild grasses gathered in the Neolithic fertile crescent.

Publications

Functional traits differ between cereal crop progenitors and other wild grasses gathered in the Neolithic fertile crescent.

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