Well...we know that there are going to be 2 civs each for every era: ancient, medieval, industrial and modern. We know that the Spanish, the Scandinavians, the Mongols, the Koreans, the Carthaginians and the Celts.
Does "Represented in four eras" mean represented EQUALLY in the 4 eras? If so we have:
ANC- Carthaginians & Celts
MED - Mongols & Scandinavians (Beserker UU)
IND - Spanish (by elimination) & ????
MOD - ????? & Koreans ?
Turks in IND and Arabs in MOD?
If the Koreans are also in it, then where would they be? The "hwacha" is apparently a medieval unit, so they must fit into the tight medieval group. Therefore, it probably doesn't mean "equally", since there would be at least 3 or 4 medieval UUs. Anachronisms are not inconceivable though, given the shocking record that the makers of civ3 have for historical accuracy.
Oh, I'm glad the Celts have been included

.
But I hope to God they don't fill the city list with insignificant Welsh towns. PLEASE... Irish, Scottish, Welsh, Ancient British and Continental cities!
Their leader is Brennus, who could either be the leader of the Gauls who sacked Rome (more likely) in 390 or the leader of the Galatians who invaded Greece in 279.