# Early Hominin Dispersal across the Qinling Mountains, China, during the Mid-Pleistocene Transition
## 3 Discussion
### The Mid-Pleistocene Transition Drove Early Hominin across the QMR  
The \"Mid-Pleistocene transition (MPT)\" was an important global climate event, which was mainly manifested in the change of the dominant periodicity of the glacial-interglacial cycles [112; 114], the significant increase in global ice volume [118], and the significant increase in the global land aridification process [119; 120; 121; 122; 123; 124]. Prior to the MPT, the climate was  
Figure 4: **Spatiotemporal distribution characteristics of hominin migration and dispersal in the QMR. ** The marine oxygen isotopes indicate the changes in the dominant periodicity of the climatic cycles (cyclicity) [106]. The black dots represent the hominin fossil and Paleolithic sites dated by our team, and the red dots represent the research by other workers. MPT, the Mid-Pleistocene transition). characterized by relatively stable cycles (approximately 41 kyr) of warm and cold periods. By contrast, during the MPT, the dominant periodicity of the climatic cycles (cyclicity) changed from 41 kyr to 100 kyr [125] (Figure 4), resulting in more extreme and prolonged glacial periods, such as the two cold and dry glacial periods that occurred at 1.162-1.080 Ma and 0.952-0.865 Ma, respectively [126]. Scholars have proposed that the migration and dispersal of early hominins in China were related to the MPT [2; 7; 10; 11; 19; 95]. [PERSON] et al. (2018) proposed that, driven by the MPT, climate change in the glacial-interglacial period intensified, and the southern QMR became a \"refuge\" for the hominins [7]. Recent studies on leaf wax isotopes in the Eastern Qinling Mountains have further supported this viewpoint [127]. [PERSON] et al. (2020, 2021) found that the geographical distribution of hominins changed across the MPT, showing a trend of southward movement [10; 11]. How did the MPT affect the course of early hominin occupation and the development of hominin adaptations? The MPT drove early hominin migration and dispersal by affecting terrestrial ecosystems [2; 7; 9; 10; 11; 12; 13; 19; 95]. Studies show that the climate became dry and cold, with forest degradations and expansions of grasslands and deserts in northern China during the MPT [128; 129]. After 1.2 Ma, the vegetation composition in northern China of alternating warm temperate forest and temperate forest was replaced by alternations of forest and grassland [128]. Changes in vegetation could then affect the species and distribution of Quaternary mammalian groups, and may have accelerated the rate of turnover of the large mammalian fauna [129; 130; 131]. The changes in terrestrial ecosystem caused by climate change would have affected the living environment of early hominins. Under the dominance of longer and colder glacial climates, the increased extreme living environmental pressure may have led to the southward diffusion of northern hominin populations. As seen in Figures 3 and 4, hominin occupation records from before the MPT were discovered in the northern QMR, but not in the southern and eastern QMR. By contrast, the hominin occupation in the northern QMR was significantly less than that in the southern and eastern QMR during the MPT. In addition, the first appearance of lithic artifacts in the southern QMR is in the L15 layer (MIS 38) (ca. 1.22-1.19 Ma) at Longgangsi-3, which could represent the start of the MPT. As a result, we speculate that, under the influence of the MPT, the ecological structure and resources of the northern QMR deteriorated, with the climate becoming dry and cold, and thus, this was not a place for permanent year-round settlement for the hominins during the longer and more severe glacial periods. Therefore, early hominins made corresponding responses and adaptations and migrated to the south, where conditions were more suitable for survival. Our team proposes that, driven by the MPT, climate change in the glacial-interglacial period intensified, and the southern QMR became a \"refuge\" for the hominins [7].