Soil temperature fluctuations modulated millet agriculture evolution in Neolithic East Asia.

Abstract

Millet agriculture was foundational to the emergence of complex societies in Neolithic East Asia, yet the environmental mechanisms shaping its spatiotemporal development remain unresolved. Here, we present a high-resolution reconstruction of Holocene growing-season soil temperature from biomarker proxies in a precisely dated loess sequence from the central Chinese Loess Plateau. Our data reveal a pronounced ~3 °C soil cooling between ~7.5 to 6.0 thousand years B.P. (kyr B.P.), followed by rapid warming and millennia-long relatively stable conditions. By integrating archaeological datasets with transient climate simulations, we show that this mid-Holocene soil cooling which reflects coupled climatic forcing and vegetation-related land surface changes likely compressed the thermally suitable niche for frost-sensitive millets, contributing to a southward displacement of cultivation and delaying large-scale agricultural expansion until the subsequent soil temperature recovery after ~6.0 kyr B.P. These findings suggest that large-amplitude soil temperature fluctuations acted as a modulating climatic constraint on the geographic distribution and development trajectory of millet agriculture in East Asia, providing refined insights into climate-society interactions during the Neolithic.