A new paper proposes that reduced solar activity after 850BC resulted in the transformation of formerly desert-like regions into herbivore-friendly wet steppes. According to this theory, the Scythian culture expanded after this time, taking advantage of the newly created steppe regions.
Journal of Archaeological Science
Article in Press, Corrected Proof
Climate change and the expansion of the Scythian culture after 850 BC: a hypothesis
B. van Geel et al.
In south-central Siberia archaeological evidence suggests an acceleration of cultural development and an increase in the density of nomadic populations around 850 BC. We hypothesize a relationship with an abrupt climatic shift towards increased humidity caused by a decline of solar activity. Areas that initially may have been hostile semi-deserts changed into attractive steppe landscapes with a high biomass production and high carrying capacity. Newly available steppe areas could be invaded by herbivores, making them attractive for nomadic tribes. The central Asian horse-riding Scythian culture expanded, and an increased population density was a stimulus for westward migration towards southeastern Europe.