Late Pleistocene climate induced changes in paleo-vegetation in Borneo: Possible implications to human divergence

Abstract

Abstract The impact of changes in vegetation on ancient human colonization and divergence in Southeast Asia is unclear. Here we present a 40 ky history of vegetation evolution in Borneo, which has been recognized as one of the hubs for early human migration, based on a pollen sequence from the southern South China Sea. Our pollen record shows that the succession of vegetation in Borneo responded to orbital climate changes as well as to the millennial-scale cold events in boreal high-latitudes in the form of upper montane taxa expansion. We find that the altitude structure of vegetation in Borneo changed from a clear altitudinal zonation of upper montane, lower montane, and lowland forests during MIS 3 to one that was dominated by upper montane forests during the last glacial maximum (MIS 2). Five expansions of upper montane forests during the past 40 ky, indicating the decrease of temperature, apparently correspond to five cold events in the northern high latitudes, with a lag of 500–1000 years. To test the influence of the changes in Borneo s vegetation on human distribution we compare our palynological data with archaeological records and the molecular evolution of ancient human genotype in Southeast Asian islands. The expansion of upper montane forests and the accompanying contraction of lowland forests in Borneo during the last glacial maximum and the last deglaciation may have promoted the divergence of human genotype. Our study offers a new perspective on the possible impact of vegetation succession on the colonization of Homo sapiens on Southeast Asian islands.