I think they were clearly making Robin not H. sap. Why else would they bother having him wear extensive facial prosthetics?
There is a point where Arrow-neck lady says she’s been there over 20 years, Noblewoman says “200”, and Roman officer says “2,000”. Caveman is standing beside him looking to be counting on his fingers and Roman officer says “2,000,000” for Caveman. But nobody literally says “Neanderthal”, and a literal two million years would be too long ago for that. He has no heavy prosthetics like Robin but has big eyebrows and prosthetic bad teeth (even though bad teeth is more of a agriculture-age affliction because of access to more sugar—if anything it should be several of the other ghosts with the bad teeth).
He has worse language skills than Robin and personality-wise is the least appealing character out of him, Robin and Thor. (His name is Urs.)
Oh, and that explaining scene (that I found again for this) is where another ghost was mentioned that I had forgotten. They say something about Delores, who died in her carriage, who travels from one wedding to the next. Not sure exactly what that is supposed to mean.