Early on Smithsonian curators and donors chose an ideology known as "Isolationism", one that suggest there was no contact between ancient cultures, that ancient man was indeed quite primitive.
"Diffusionism", to quote Childress again, is "a
school which believes that throughout history there has been
widespread dispersion of culture and civilisation via contact by
ship and major trade routes.
Call it professional arrogance, call it elitism, call it what it is, over the years many anomalous artifacts and even entire archaeological dig sites have simply disappeared from the record, from the earth, supposed to have been kept safe by the Smithsonian Institute. The Isolationist theory was/is so strongly espoused that they may have gone so far as to destroy evidence to the contrary.