In my new capacity to close vote without undue weight, I feel the need to revisit a previous question about the close reason, "Primarily Opinion Based".
How does one know what one doesn't know?
I don't want to insult anyone, but We Are All Confident Idiots* (and I am no exception) is an interesting read, and would make for some potentially beneficial required reading before voting (or answering) on any SE site.
The problem I see in voting to close due to POB is that a vast amount of information exists on almost every aspect of human health. Just because someone doesn't know how to search the database doesn't mean the answer (with evidence to support it) isn't out there.
An example: Can ingesting a mosquito make you sick? The answer to this (with reference to HIV specifically) is not Primarily Opinion Based. The research on risk of acquiring HIV from various exposure modalities is more than encyclopedic. Risk of acquiring the infection from ingestion is certainly available. That means there's fact-based evidence for an answer. (You - or I - may not want to answer it, or may think it's a trivial question, but it's not POB.)
https://health.stackexchange.com/q/4217/169 is not Primarily Opinion Based. It might be unclear what the OP is asking, but the literature on bone structure variation (especially in physical anthropology) is vast.
I've seen questions closed on another site as POB which I know has an evidence-based answer. The problem is that people who don't know that studies have been done on something they're unfamiliar with think it's POB.
I'm not saying that people can't close questions as POB. But I'm wondering: can we come up with guidelines for deciding if a question is POB or just a head-scratcher?
*A quote: Because of the way we are built, and because of the way we learn from our environment, we are all engines of misbelief. And the better we understand how our wonderful yet kludge-ridden, Rube Goldberg engine works, the better we — as individuals and as a society — can harness it to navigate toward a more objective understanding of the truth.