Are these tags too specific, or are they fine? If they're okay, should there be other related tags? (I know we already have ancient-greece)
Thinking about it, I think the temporo-location based tags are actually okay - as they convey a time and place where the particular discovery was developed/made/etc.
However, I would say that these should always be used in conjunction with a discipline based tag such atmosphere or medicine etc. Even a third tag, providing some more detail such death can nicely categorise a question.
Omen speaks well on the conjunction comment. That whole statement is spot on and key. Even if these minor tags stick around, it should be noted in the tag description that these sorts of tags should never be used alone, but always with a higher level tag.
This is an example of a great question that might need a higher level tag alluding to the history of science in this case. I am not sure, if one sees (nazi-germany) as being a solo top tier tag, then we are ok, but I would come up with a second science related tag for this. It might be (space-program) (I like that!), (rocket-science), (space-science), (space), or, well I'll let you decide, but ideally everything should be tagged with some high level tag that makes it clearly a site relevant question, and does not cause it to be tagless in the event of a mass tag deletion.
Tag creation is no small matter, and I am no better at it than anyone else. It boils down to making that major tag something that fits a broad group of site relevant questions. We can replace tags with others later if necessary, so not to worry too much, but that should be considered when creating one of these new broad tags that you're not sure about.
While we have time, I would not let the number of questions hit 5000 before deciding to kill certain tags (case by case judgement call) and ensure that every question has our higher level tags (Osiris may we meet that many questions).
If everything is marked with our higher level tags, this will mean that killing a particularly useless tag sitewide later on will not leave tagless posts everywhere. This could be a particularly unpleasant situation to repair.
Tag cleanup can just get downright ugly eventually if neglected. Minor tags can be useful within reason, and time will tell. I think this question is pretty crucially important. Other sites spend and have spent enormous amounts of time on tag cleanup, and encounter all sorts of problems in that effort when tag management is neglected for too long.
I would probably leave some of these tags for a while, and kill the ones where it is evident that the tag will not really populate over the long term with a substantial number of questions. We have time, but this is something to keep an eye on, and definitely something to keep asking as time goes on.
Eventually, we might (optional, typical on other sites) put some proposed tag deletions (or synonym replacements sometimes) here in meta. If you see a particularly horrible tag, you might given your privileges just delete or propose to delete immediately. This will be an ongoing issue.
As far as your sample lesser tags go, I would wait a bit. Some or all of them might prove to be real hits in time. Time will tell, and if otherwise tagged correctly with other tags, a deletion later on will not cause so much trouble.