Liza May, 2 bits to clarify:   I know of no citified/literate culture
EXCEPT (but) Indus etc;   and I didn't say ball lightning doesn't
exist, but on the contrary that it most likely does.
   Neither the evidence for its existence, nor supposed quantum
electrodynamics explanations, get us much beyond gee whiz.
   As for Shumer or Sumer (students of the area say it was pronounced
Sh), it's the first known urban culture apart from a Jericho shrine.
Ur and Uruk may be the oldest towns humans lived in.
   The 'issue' to be clarified about Indus River culture is how it
developed; reading the language will help.  I was responding to
assertions about UFOs' alleged intrusion into human history.
   Oh, and Zyklon B was used in Nazi death camps.

  Pet