The relationship between the Indo-Asian Monsoon and regional tectonic uplift is a leading example of the interaction between geological and climate processes on long time-scales. We present results from a high-resolution global climate model, developed by NCAR (CAM4), at 25 km resolution. Counter to the previous notion on what controls the Indo-Asian Monsoon, we provide evidence that the monsoon onshore flow is maintained without the Himalayan Mountains, nor the Tibetan Plateau. Instead, the flow is influenced by the Western Ghats and Mizoram mountains. However, rainfall across the northern Indo-Asian monsoon sector only occurs when the Himalayan Mountains or the Tibetan Plateau is present due to the terrain readily lifting the moisture-laden flow. Results from our study demonstrate that some aspect of the Indo-Asian monsoon should have existed during the early Paleogene, prior to any regional tectonic uplift.