 The onset mechanism has long been debated and remained poorly understood.On one hand, it is believed that the uplift of the Himalayas and Tibetan Plateau is the major trigger of South Asian monsoon onset, since only such elevated landmass can change regional airflow configurations.On the other, numerical modelling and thermalchronological data suggest that Eocene uplift of the Himalayas and Tibet is driven by monsoon-intensified denudation, i.e.