[@Raylah] I suppose that means that by handpicking specific people with specific genetic traits and specific skills, you can basically min-max the amount of people needed for the highest chance of diversity. Whereas in an extinction level event, every Bob, Joe, and Marie need to procreate, and Bob and Joe are both farmers, and Marie is their cousin. :lol 

Also, I think the den you're referring to might be similar to the den of a beaver? [url=https://www.oec-eng.com/mundooec/sites/default/files/inline-images/5.jpg]This[/url] might be a dope way for the earliest amphibious civilizations to live at the start. :lol