Damn those Dams!

Dams were invented centuries and centuries ago as an instrument to prevent water from flowing into the land where people lived. Both humans and animals use dams (think beavers), but over the years, humans took dams to a level where it has a negative environmental impact. One of the affects is fish not being able to breed correctly, and therefore causing some species to become endangered and sometimes extinct. Aren't humans being selfish by being too afraid to get a little wet, even though it means that species of fish will die off? I think something needs to be done about the dams so that they don't affect life underwater.