Late Pliocene-Quaternary climate-environment evolution on the southeastern Tibetan Plateau and links to hominin dynamics

• Chemical weathering intensity decrease on the SE Tibetan Plateau since Late Pliocene. • Pliocene-Quaternary three hominin dispersal events in Africa and Asia are identified. • Northern Hemisphere ice expansion and Indian monsoon decrease are driving forces. The southeastern Tibetan Plateau (TP), a key region for hominin activities, holds crucial information for investigating climate-environment evolution and its impact on biological evolution. However, previous studies primarily focused on the Miocene-Pliocene interval, with limited evidence spanning the Late Pliocene-Quaternary interval—a period of critical global climate transitions from a unipolar to a bipolar ice sheet world. To address this gap, we conducted short-wave infrared (SWIR) spectroscopy and clay mineral analyses on Late Pliocene-Quaternary sediments within a drilling core from the southeastern TP region, and re-examined hominin evolution and migration patterns over this time interval. Our proxy results indicate a secular decrease in chemical weathering intensity on the southeastern TP since the late Pliocene, trending towards drier and colder conditions, with two accelerated decreases at around 2.8 Ma and 1.1 Ma. We link these changes to weakening of the Indian summer monsoon (ISM) induced by the Northern Hemisphere ice expansion, based on their consistent temporal variations and similar periodicity characteristics. A re-examination of fossil records in ISM-influenced Asia and Africa regions reveals three main hominin dispersal/evolution events at 3.0–2.8 Ma, ∼2.6–2.4 Ma, and ∼1.1 Ma, which coincide with the ISM weakening events in the obtained records. We suggest that the habitat fragmentation and environment transitions induced by ice expansion and ISM weakening promoted diversification of hominin behavior and ecosystems, and ultimately influenced the dispersal/evolution of hominin species.