“This question have been asked before and already has an answer” duplicate of a future post? [duplicate]

Question

This question already has an answer here:

• Should I vote to close a duplicate question, even though it's much newer, and has more up to date answers? 4 answers

I've seen the behavior on occasion and are a bit curious of the ruling. How can a post be marked as a duplicate of post which wasn't there at the time of the original post? The most recent example I've seen is this:

Why does Stack Exchange require you to click to be turned down?

Posted February 12 and marked as a duplicate of

Why are vote buttons on Stack Exchange shown when they can't be used?

Posted March 14.

I'm told its because the second post had better answers. I'm curious if this is correct. Shouldn't the answers on the later question be merged to the first one, which is the original one?

Answer 1

Who is better off if we direct future visitors away from the question with quality answers and to the question without as high a quality of answers?

Why does a question being asked first mean it should remain open?

You should always keep whatever question is most valuable open, and close any duplicates as duplicates. If there are multiple questions with valuable content, then the posts should be merged. Again, here whichever post is more valuable should have the other post's content merged into it. Keep around what is of the highest quality, not what is the oldest.