OK, I know the answer now.
Both barb production and Advanced Trbe creation hinges only on one thing.... the founding of your first city. After you found your first city, ATs and barbs (1 horseman) can be produced.
All tests at Deity, 7 Civs, Raging hords, 100% Plains, MGE.
Here is another run (At game turn 15) of all 125 before founding 1st city:
Units:
14 Archers
14 Horsemen
20 Legion
09 Chariot
15 Elephant
00 Nomands
00 Empty Huts (same in 1st run, even though I didn't mention it)
00 Barbs
00 Advanced Tribes
1600 Gold
25 Advances (Ended at about #122 with the advance of Invention, which prevents further Hut advances)
AFTER FOUNDING 1ST CITY
Here are several runs after founding the 1st city, generally until the 1st barb:
Hut #7, 9, 11, & 13 = ATs; #14=Barb
Hut #5, 6, 7, & 9=ATs; #10=Barb
5=AT, 8=B
5=AT, 8=B
2=Barb
2=B, 4=B, 5=AT
4,5=AT; 6=B
Hope that helps hut poppers with the odds.
