The establishment of major rivers in Asia is often attributed to tectonic-driven topographychanges associated with Tibetan Plateau growth. However, it is unclear whether the globallyaccelerated erosion related to climatic instability since the Pliocene is an importantmechanism for river evolution. Here we present detrital-zircon age data from three well-datedboreholes in the lower floodplain of the Yellow River (YR) to constrain the timing of theintegration of the YR, one of the longest and the most sediment-laden rivers in theworld. Our results show significant provenance change at 1.5 Ma corresponding tothe final integration of the Upper and Middle Reaches to the Lower Reaches ofYR, through the incision of the Sanmen Gorge. This late integration of the YRnotably lags significant uplift of the northeastern Tibetan Plateau, precluding atectonic driver. Our results rather suggest that Plio-Pleistocene increasing climateinstability and sea level fall significantly enhanced headward incision finally cuttingthrough the Sanmen Gorge to integrate the whole drainage system at 1.5 Ma. [ABSTRACT FROM AUTHOR]