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Catastrophic fires and soil degradation: possible link with Neolithic revolution

Purpose The agricultural revolution of the Neolithic period in the Levant has puzzled researchers trying to resolve climatic vs. anthropogenic chain of events. The paper deciphers the probable natural causes of the Neolithic revolution, using various records from the southern Levant which point to catastrophic fires and soil erosion. The paper also underscores the observation that Neolithic sedentary farming communities in the southern Levant concentrated over water-rich reworked sediment accumulations, which could be readily cultivated. Materials and methods The reviewed records include counting of micro-charcoal particles in a sedimentary core from Lake Hula, Carbon and Strontium isotopes in speleothems, OSL ages of soils underlying terraces, and lake level fluctuations of the Dead Sea. These are supplemented by new sedimentary observations in various environments, which show a thick accumulations of reworked soils in various sedimentary traps, associated with Neolithic settlements and overlying late Pleistocene Lake Lisan deposits. Results and discussion Extreme peaks of micro-charcoal and speleothem δ13C are explained by fires, causing removal of vegetation and soil. Increased lightening intensity was probably the main igniting cause. A pulse of low 87Sr/86Sr ratios and sedimentary sections indicate that soil was eroded from hillslopes and redeposited in sediment traps such as valleys. The low 87Sr/86Sr values correspond to the entire Neolitic period. An increase in lightening thunderstorms was associated with the orbital-forcing-controlled high solar radiation during the early Holocene, causing a short-term marginal penetration of southern climate systems into the southern Levant, culminating between ~ 8 and 8.6 ka. Low Dead Sea levels indicate that this period was dry, coeval with the 8.2 ka cold and dry event of the northern hemisphere, possibly amplifying the catastrophic effects. Conclusion The various records infer that the environmental catastrophes resulted from a climatic shift, rather than an anthropogenic cause, such as intentional burning. Increased lightening intensity promoted an intensive fire regime which caused major loss of vegetation and soil degradation, enhancing and possibly causing the Neolithic revolution. Unprecedented human behavior, such as farming and domestication of plants and animals, could be influenced by the severe environmental deterioration.

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