Preheat oven to 350ºF. Grease 2 loaf pans, (8-by-4 or 9-by-5).
Whisk together the flour, baking soda, salt, baking powder, and spices in a medium bowl. In a separate large bowl, beat the sugars, oil, and eggs until well combined. Add the pumpkin and mashed banana, mixing until smooth. Gently stir in the dry ingredients, then fold in the pecans until evenly distributed.
Divide the batter evenly between the prepared pans and smooth the tops. Bake for 45–60 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs. If the tops begin to brown too quickly, loosely tent the pans with foil during the final minutes of baking.
Cool in pans for 5 minutes. Run a knife around the edge and pop out of pans. Cool on a wire cooling rack.
Serve warm or at room temperature. Wrap bread in foil to store.