Tequila!
Maybe they’re excited about Halloween coming?
Neanderthal man is dancing with a close relative taken from Man from the Farthest Path, volume 7 in the Smithsonian Scientific Series, with then-Secretary of the Smithsonian Charles Greeley Abbot as editor-in-chief.
View the book at http://library.si.edu/digital-library/book/manfromfarthestp07bish.
"Man From the Farthest Past," volume 7, by Carl Whiting Bishop. Smithsonian Institution Series, Inc., 1930
