The current close reason is "too broad".
The description of "too broad" is:
There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.
For this question, there is, by definition, exactly one answer that is correct at any given time.
Good answers would, imo, describe a likely candidate for the correct (see above) answer, and possibly two or three other close contenders, along with an explanation as to why they believe those suggestions fit/do not fit the criteria.
Put simply, "too broad" doesn't apply here.
It's not a duplicate (afaik).
It's not primarily opinion based: answers could easily be supplemented by facts, numbers, and direct comparisons, so while opinion may be part of some answers, it isn't primarily opinion based.
It's pretty clearly not off topic (science fiction alien races).
It is not unclear.
I disagree with the closure, and have voted to reopen.