The Secrets Hidden in Hazelnuts: A Glimpse into Ancient Woodlands

An archaeologist employs pollen samples extracted from the soil to unravel the evolving plant life of a location, complementing the author's study on the analysis of hazelnut shells. (Credit: Nils Forshed)

Imagine stepping into the landscape our Mesolithic ancestors once called home. What would surround us? Scientists have ingeniously crafted a method to unravel this mystery by scrutinizing preserved hazelnut shells. These tiny artifacts hold the key to understanding the microhabitats surrounding archaeological sites, revealing whether they were densely forested or open pastures. This analysis not only paints a vivid picture of the environment thousands of years ago but also sheds light on how human activity has shaped these landscapes over time.

Dr. Amy Styring, lead author of the study published in Frontiers in Environmental Archaeology, explains, "By examining the carbon content in hazelnuts recovered from various archaeological sites in southern Sweden, ranging from Mesolithic hunter-gatherer camps to one of the largest Iron Age settlements in northern Europe, we can deduce that hazelnuts were gathered from increasingly open environments."

Neolithic Nutella

The hazel tree has been a cornerstone of human life in northern Europe for millennia, serving as a vital source of sustenance and materials. For those who gathered hundreds of hazelnuts at Mesolithic and Neolithic sites, these nuts were a prized commodity.

Dr. Karl Ljung, senior author of the study and a researcher at Lund University in Sweden, explains, "Hazelnuts are rich in energy and protein, making them an excellent food source that can be stored for extended periods, either whole or ground into a paste. Additionally, the shells could have been used as fuel."

Every plant, including hazel trees, contains carbon, which exists in various forms known as isotopes. The ratio of these carbon isotopes is influenced by the concentration of carbon dioxide within the leaf cells and the surrounding environment. In plants like hazelnuts, this ratio is heavily influenced by sunlight and water availability. In areas like Sweden, where water is abundant, sunlight plays a more significant role in determining the ratio. In places where other trees are scarce, allowing more sunlight to penetrate the canopy and enhancing photosynthesis rates, the hazel trees will have higher carbon isotope values.

Ljung elaborates, "This means that a hazelnut shell discovered at an archaeological site can provide insights into how open the environment was when it was gathered, offering clues about the habitats where people foraged."

Through this innovative method of analyzing hazelnut shells, archaeologists can peer back in time and reconstruct the landscapes of ancient civilizations, uncovering the intricate relationship between humans and their natural surroundings.

Unraveling the Past: Insights from Hazelnut Shells

To explore the correlation between light exposure and carbon isotope values in hazelnuts, researchers collected nuts from trees growing under varying light conditions at three sites in southern Sweden. They then studied the carbon isotope values of hazelnut shells from four Mesolithic sites and eleven sites spanning from the Neolithic to the Iron Age, some of which were occupied in multiple periods.

Based on the findings, a model was developed to categorize the samples into three groups: closed, open, and semi-open environments. Since the carbon isotopes of individual hazelnuts naturally differ slightly, multiple samples from each site were used to determine the proportion of nuts grown in closed or open areas.

The study revealed a significant shift in hazelnut collection practices over time. During the Mesolithic period, nuts were primarily collected from closed environments, while in later periods, they were gathered from more open areas. By the Iron Age, most nuts were collected from open areas rather than woodlands, indicating a complete shift in microhabitats. This finding aligns with pollen analyses and demonstrates the potential of isotope analysis in visualizing local environments where pollen records are limited.

Dr. Styring remarked, "Our study has paved the way for directly linking environmental changes to human foraging activities and reconstructing the microhabitats they utilized. We aim to expand our research to include a wider range of archaeological sites and settings, enabling a more detailed understanding of past woodlands and landscapes. This knowledge can enhance our understanding of human-environment interactions and inform modern-day woodland management."

The paper titled "Carbon Isotope Values of Hazelnut Shells: A New Proxy for Canopy Density" was recently published in the journal Frontiers in Environmental Archaeology (2024). The DOI for this study is 10.3389/fearc.2024.1351411. The research explores the potential of using the carbon isotope values found in hazelnut shells as a means to estimate canopy density in archaeological sites.


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