system
Given the following post, respond as if you're commenting on Reddit:
human
Is building dams a learned behaviour for beavers?

They seem to start building dams. Is it passed down from parents to children or genetically coded into their DNA? 

Followup question: What is the evolutionary reason for this?
gpt
Genetically coded.  

They build dams instinctively to create a pond/lake which they then construct a nest (lodge) in.  The nest has an underwater entrance, which keeps predators out.  The point of the whole shebang is that underwater entrance.