Data from different disciplines are integrated and used to propose an alternative hypothesis regarding the Upper Weichselian environmental developments in the central Scandinavian mountains. This hypothesis, which tries to integrate new and controversial finds and explain them in a new light, is far from proven and needs much further research. It is proposed that parts of the mountains have been glacio-isostatically more depressed than previously thought and that the glacial dynamics could have been much more pronounced than traditionally assumed. As a consequence, it is proposed that Baltic-Bothnian water crossed temporarily ice-free areas with low-altitude thresholds across the Scandinavian mountain range, sporadically allowing drainage towards the Atlantic Sea, and even that Atlantic water could temporarily have entered into Sweden from the west. Such land-water scenarios could have resulted in a water transport system that steered floating tree seeds and sprouts, transported by rivers from central Europe and/or by seawater from the Atlantic, into the mountain range. There, high isostatic rebound rates during early deglaciation phases could quickly have made coastal areas become land, allowing plants to start their life cycle almost immediately.