Widespread reports of godlike beings.
Global similarities in myth and symbol.
Commonalities of ancient language.
How civilizing attributes, such as masonry styles were communicated between widely distant cultures.
What the source may have been of ancient maps that are longitudinally correct.
What the source may have been of widespread artistic representations of anomalous beings.
The derivation of widespread artifacts that would seem to require technology for their production.
The origin of concepts of creation that often seem scientific.
Unexplained knowledge of astronomic facts in various cultures.
Artistic representations of what might be taken as aerial craft.
The unexplained presence of various types of artifacts in unexpected geographical locales.
Timing discrepancies in the transmission of techniques or concepts between cultures.