"Man knows nothing"

In the Viking Ship Museum in Oslo, Norway, I noticed a small exhibit - a piece of wood bearing this runic inscription.  The explanatory note by the exhibit translated the inscription as "man of limited understanding." Attracted by that notion, I found that the museum gift shop were selling T shirts with the runes but, on the back, a different translation - "man knows nothing," which is ambiguous.

My interpretation is that "man" here means "humanity" or "people." On that basis, I think this qualifies for today's Mono Monday challenge - people. Or, maybe, I know nothing. Thanks to Skeena for doing the hosting honours.