seasnake
Conquistador
There seems to be fifteen civs per era in the base game, and each civ seems to be associated with a wonder. At the 1h57 mark in this video by Ursa Ryan (), he displays all the wonders he could find in the civilopedia. This leads me to belive that the era 1 civs are:
-Rome (Colosseum)
-Greece (Colossus)
-Assyria (Dur-Sharrukin)
-Silla (Emile Bell)
-Axum (Grea Stele)
-Tonga (Ha'amonga 'a Maui)
-Babylon (Hanging Gardens)
-Ostrogoths (Mausoleum of Theodoric)
-Gupta (Nalanda)
-Nabateans (Petra)
-Teotihuacans (Pyramids of the Sun)
-Egypt (Pyramids)
-Maurya (Sanchi Stupa)
-Qin (Teracotta Army)
I'm a bit iffy on the teotihuacans because as far as I'm aware there is only one pyramid of the sun there, and maybe Qin and Silla are referred by the name of other dynasties or kingdoms. If I'm right, however, this lends credence to the idea that leaders and civs are divorced, since we know Confucius will be a leader, and he lived under the Zhou dynasty.
I don't think every Wonder implies a corresponding civilization, at least I didn't see anything confirming that. In past games there were frequently multiple wonders that either had no civ, or came from the same civ. Absent something confirming a 1 to 1 corollary, I wouldn't take this to mean all these civs are in.