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Grape and olive farming traditions have changed through time based on shifts in climate and the needs of the local culture, according to a study published in the open-access journal by Simone Riehl of the University of Tübingen, Germany and colleagues.

Throughout human history, olives and grapes have been important crops thanks to their nutritional value, symbolic significance, and key role in the production of valuable trading goods such as olive oil and wine. The availability of these crops, however, has fluctuated over time with changes to culture and climate.

In this study, Riehl and colleagues compiled data from archaeological sites across the Levant and northern Mesopotamian regions to assess how agricultural practices have changed over time.

The authors analyzed over 1,500 seed and wood samples from the Early Bronze Age to the Iron Age, measuring stable isotopes of carbon as an indicator of moisture availability during the growth of the plants.

During the Early Bronze Age, evidence of water stress matches seasonal moisture variations, but during later periods, greater variability in water stress and the presence of these crops in drier regions indicates more widespread use of irrigation practices. Periods of increased crop stress also line up with well-documented climate fluctuations.

These results provide a wealth of new data for examining how agricultural practices have been impacted over time by changing climates and farming techniques.

Since the Middle Bronze Age, abundant evidence for intense irrigation of grape crops, as well as the presence of cultivated grapes even in poorly-suited climate zones, indicates a stronger commitment to viticulture compared to other crops such as olives. This pattern suggests that grapes and wine were of particular cultural and economic value, consistent with previous archaeological research.

The authors add, "Our research demonstrates that farmers in Southwest Asia 4,000 years ago were making decisions about which crops to plant and how to manage them, balancing the risk of harvest failure with the effort needed to irrigate, and the likely demand for their products. It reminds us that people in the past were just as smart as people today, and that seemingly modern issues like resilience to climate change and the need to allocate resources carefully have long histories."