Human-environment interactions within the West Liao River Basin in Northeastern China during the Holocene Optimum

Cultural studies of Neolithic China have focused on the social aspects and the human–environment interactions associated with those cultures. However, the uneven spatial distribution of Neolithic sites in Northeastern China has not yet been explored. This study traces the relationship between human settlement patterns and the agro-ecological environment during the Holocene Optimum, based on the spatial distribution of 4184 Neolithic sites, together with optically stimulated luminescence (OSL) dating and pollen analysis of five profiles and 22 plant flotation samples from 10 of the archaeological sites in the West Liao River Basin, the hub of Neolithic Cultures in Northeastern China. The overwhelming majority (∼96.7%) of the Neolithic sites are located south of 43º30′N latitude in the West Liao River Basin on the southern fringe of the Horqin Dunefield. The dunefield, which has been commonly hypothesized as vegetated during the Holocene Optimum, was a typical steppe at that time and not suitable for growing millet, the primary staple crop of Neolithic Cultures. Our results and other archaeological site records reveal that the 43°30′N latitude was a remarkable barrier for the dispersal of human settlements in Northeastern China during the Neolithic Age. The barrier was probably formed by the low frost tolerance of millet and the temperature gradient associated with the latitude, making large-scale agricultural production impossible in the regions north of this latitude at the time. Our findings provide evidence for the natural northern limit of Neolithic Cultures in Northeastern China during the Holocene Optimum.