New documentation of dramatic climate changes at the end of the last ice age is shedding light on our ancestors’ transition from nomadic hunter-gatherers to a farming society.
Based on the identification of plant remains, Tel Aviv University and Tel-Hai College researchers provide the first detailed reconstruction of the climate in what is now Israel at the end of the last ice age (20,000-10,000 years before present).
The researchers claim that significant climate changes characterizing the period, manifested by sharp differences in temperature and precipitation not only seasonally but throughout the year, were a significant influence in the transition from a nomadic hunter-gatherer society to permanent settlement and an agricultural way of life. The study also provides the first information pertaining to the history of the region’s flora and its response to past climate change.
The research was conducted by Dr. Dafna Langgut of the Department of Archaeology and The Steinhardt Museum of Natural History at Tel Aviv University; Prof. Gonen Sharon, Head of the MA Program in Galilee Studies at Tel-Hai College; and Dr. Rachid Cheddadi, an expert in evolution and palaeoecology, University of Montpellier, Institute of Evolutionary Sciences (ISEM) Montpellier, France. The study was recently published in the leading scientific journal Quaternary Science Reviews.
Study identified ancient plant remains
The study, “Climate and environmental reconstruction of the Epipaleolithic Mediterranean Levant (22.0–11.9 ka cal. BP),” was conducted at the prehistoric archaeological site Jordan River Dureijat (Jordan River Stairs) on the shores of the Paleo Lake Hula. The study is based on a well-dated, high-resolution pollen record recovered from the waterlogged archaeological site. The site is unique for its exceptional preservation conditions yielding finds that enabled the discovery of the primary activity of its early local residents – fishing.
Botanic remains preserved also enabled researchers to identify the plants that grew 10,000-20,000 years ago in the Hula Valley and its surroundings.
Taxonomic identification of the waterlogged wood collected from the site was used to fine-tune the paleoenvironmental reconstruction. The chronological framework is based on radiocarbon dating and the typology of archaeological findings.
Two major processes in world history took place during this period: the transition from a nomadic to a settled lifestyle that occurs during a period of dramatic climate change.
“In the study of prehistory, this period is called the Epipalaeolithic period. At its outset, people were organized in small groups of hunter-gatherers who roamed the area. Then, about 15,000 years ago, we are witness to a significant change in lifestyle: the appearance of settled life in villages, and additional dramatic processes that reach their apex during the Neolithic period that followed. This is the time when the most dramatic change of human history occurred – the transition to the agricultural way of life that shaped the world as we know it today,” said Sharon, who also is the supervisor of the Madregot Hayarden excavation.
Medthodology: Building a climate model
“Although at the peak of the last ice age, about 20,000 years ago, the Mediterranean Levant was not covered with an ice sheet as in other parts of the world, the climatic conditions that existed nevertheless differed from those of today,” explained Langgut, an archaeobotanist specializing in the identification of plant remains. “Their exact characteristics were unclear until this study. The climatic model that we built is based on reconstruction of the fluctuation of the spread of plant species indicating that the main climatic change in our area is expressed by a drop in temperature (up to five degrees Celsius less than today), whereas the precipitation amounts were close to those of today (only about 50 mm less than today’s annual average).
However, Langgut added that about 5,000 years later, in the Epipalaeolithic period (about 15,000 years ago) a significant improvement in climate conditions can be seen in the model.
According to the researchers, an increased prevalence of heat-tolerant tree species, such as olive, common oak, and Pistacia, indicate an increase in temperature and precipitation. During this period, the first sites of the Natufian culture appear in the region. And, it could very well be that the temperate climate assisted in the development and flourishing of this culture.
Study examines the local Younger Dryas period
The next stage of the study deals with the end of the Epipalaeolithic period, about 11,000-12,000 years ago, known globally as the Younger Dryas period. This period is characterized by a return to a cold, dry climate like that of the ice age, causing somewhat of a climate crisis around the world. The researchers claim that until this study, it was unclear whether, and to what extent, there was any expression of this period in the Levantine region.
According to the researchers, the findings that arise from the climate model presented in the article show that the period was characterized by climatic instability, intense fluctuations, and a considerable drop in temperatures.
Nevertheless, while reconstructing the precipitation, a surprising phenomenon was discovered: the average quantities of rainfall reconstructed were only slightly less than those of today; however, the precipitation was distributed over the entire year, including summer rains.
The researchers claim that such distribution assisted in the expansion and thriving of annual and leafy plant species. The gatherers who lived in this period now had a wide, readily available variety of gatherable plants throughout the entire year. This variety enabled their familiarity just before domestication. The researchers are of the opinion that these findings contribute to a new understanding of the environmental changes that took place on the eve of the transition to agriculture and the domestication of animals.
“This study contributes not only to understanding the environmental background for momentous processes in human history such as the first permanent settlement and the transition to agriculture but also provides information on the history of the region’s flora and its response to past climatic changes. There is no doubt that this knowledge can assist in preserving species variety and in meeting current and future climate challenges,” said Langgut.
• Pollen-based paleoclimate model (∼22.0–11.9ka) is provided for the southern Levant.
• Lowest January temperatures were reconstructed during the LGM (5 °C lower than today).
• The lowest climatic seasonality contrast was reconstructed at the Younger Dryas.
• A robust environment set is suggested for the rise of sedentism and agriculture.
• A confluence of natural changes and cultural developments promoted agriculture.