system
Given the following post, respond as if you're commenting on Reddit:
human
How many times would the word "great" need to prefix grandmother/father in order for me to be talking about a waterborne ancestor?
gpt
If you want to go back to the first tetrapods, then you're about 390 Ma. In human generations, assuming 25 years for a generation, you have about 16 million generations (15,999,998 greats, if you will). 

However, this is very rough and only based on a human generation. Your ancestors didn't have the same lifespan, so there would be many more greats thrown in there.

This is actually a nice visualization of how, when people say "look, there's no evolution happening", you can just tell them that the length of time evolution operates is staggeringly long.