Using a map from the first major study of beavers from 150 years ago, scientists have found that beaver dams can last centuries.
The researcher who produced the original map, Lewis Henry Morgan, had himself theorized that beaver dams were long-lived. This study proves it. Then again, it makes sense, since geography is going to limit the right locations for a dam. The right place is always going to be the right place, and thus the new study proves that generations of beavers go back to the best locations repeatedly.