I came across this "How did the human brain evolve?" question. It is a 7-year-old question with about 16 upvotes. It is a great example of the Q&As I am talking about. Evidently, the answers are insufficient, albeit also upvoted. They either talk about a specific gene, or very general concepts. This is of course what we have observed time and time again and why we have a close option for broad questions.
I thought about voting to close on the basis that it is too broad, but this has about 1k views and a lot of upvotes so clearly has value on the site.
Why these questions exist
There are many other questions like this that were made before Bio.SE left beta. Before beta, the rules were different and the aim of the game is to see which questions work and which don't. Closing wasn't so clear-cut because we didn't know which questions would eventually lead to good answers.
Should we be closing these "old but gold" questions as they turn up, or just let them be?