During the early Oligocene, an area in southwestern China had a humid subtropical climate with weak monsoon characteristics. By studying ancient plant fossils, researchers found evidence of hot summers, warm winters, and subtle monsoon influences. The plants adapted to monsoon conditions, similar to those in Indonesia and Australia today. The study suggests that the region was at a mid-altitude and experienced a drop in elevation after the early Oligocene. This research helps us understand the climate and landscape changes in this area millions of years ago.