viernes, 30 de mayo de 2014

Neolithic Near East wetter and more fertile than today

A new study describes the characteristics of agriculture at its beginnings by comparing kernel and wood samples from ancient Near East sites, with present day samples. It is the first time that direct evidence is able to reveal humidity and fertility conditions of crops, as well as the process of cereal domestication developed from the Neolithic (12,000 years ago) to early Roman times (around 2,000 years ago).
The study was co-directed by Josep Lluís Araus, professor from the University of Barcelona (UB), Juan Pedro Ferrio, Ramón y Cajal researcher at Agrotecnio of the University of Lleida (UdL), and Jordi Voltas, professor from Agrotecnio. The study has been published in the journal Nature Communications. Researchers Ramon Buxó, archaeologist and director of the Archaeological Museum of Catalonia-Girona, and Mònica Aguilera, UdL researcher who is now working at the Paris Natural History Museum, also participated in the study.
Researchers used crop physiology techniques to analyse archaeobotanical remains. In total, they looked at 367 barley and wheat kernels, and 362 wood samples obtained in eleven archaeological sites from Upper Mesopotamia (including present day south-eastern Turkey and northern Syria).

Progressive domestication

Researchers compared the size of kernel remains with present day samples to determine the evolution of crop domestication. “The methodology used to date does not reproduce real size; it measures width and length of charred kernels”, explains Josep Lluís Araus. “We have reconstructed cereal kernel weight and have seen that it increased for a longer period of time than it was thought, probably during several millennium”. According to the researcher, the initial selection of kernel was “unconscious”, in other words, the first farmers selected the biggest kernels, so size increased progressively.

Wetter and more fertile soils

Sample analysis of carbon and nitrogen isotope compositions —a technique used in crop physiology and improvement— was a key factor to describe the conditions of the area. “Carbon isotope composition enables us to evaluate water availability for crops. It reached its maximum level 9,000 years ago, and then it decreased progressively until the beginning of our times”, explains Araus. However, researchers have not found conclusive evidence that irrigation was a common practice. “This information together with cereal kernel weight allows us to assess the productivity of ancient crops”, highlights Josep Lluís Araus.
Nitrogen isotope composition provides information about the soil’s organic matter and fertility. Juan Pedro Ferrio (Agrotecnio-UdL) affirms that “although they were dryland crops, it can be ascertained that nitrogen was much more available than today: undoubtedly, soils were much more fertile than nowadays”. Moreover, a progressive decrease in soil fertility can be observed, probably due to over-exploitation or the use of less fertile soils, but also to more extreme climate conditions.

Evolution of human communities

These data enable the researchers to describe more precisely agronomic conditions and the evolution of human populations linked to agricultural practices. “The study relates conditions like water availability or soil fertility to crop yield”, says Araus. Past yields, compared with average calorie needs of one person, enable the researchers, for example, to have a rough idea of the crop area needed to feed the population. “This information can be used to know more precisely the borders of past settlements and the evolution of human communities. The aim is to include all this information in models in order to better understand the past.”

Source: Past Horizons:

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