The object of the game is to be the first player to the end of the Archaeological Succession Table, which is basically a turn record track. However, at several points along each track, certain conditions have to be met before you can advance any further, such as your first hurdle being the need to have 2 cities in play.

Each player begins in the same way, by placing one unit on the board, which represents a nomadic tribe. Each round of play has 13 phases, which must be performed in order. Early on, most of these are skipped, giving a nice learning curve to the play of the game. These phases are as follows:

Collect Taxes - Players pay 2 for each city they have.
Population Expansion - Each area with a token gains another, each area with two or more tokens gains two.
Census - Each players tokens are counted. The player with the most moves first.
Ships - Building ships costs 2, and allows tokens to move further. Existing ships have to have 1 upkeep paid to keep them on the board.
Movement - Tokens are moved into adjacent areas, while ships move up to 4 water areas. Or tokens can embark on a ship.
Conflict - Opponents pieces in the same area conflict if there are more tokens in that area than the area can support (Each area can only support a certain number of tokens). Simply alternately remove tokens until only one players tokens are in the area or the population limit is no longer exceeded.
Build Cities - If six tokens are in an area with a city site, they can be exchanged for a city. Elsewhere, it takes 12 tokens.
Remove Surplus Population - Each area is checked. If there are more tokens in an area than it can support, the excess are removed.
Unsupported Cities - Check for City Support. Each city needs 2 tokens in play to support it. If a city is unsupported, it has to be reduced to the token limit for that area. (Can be nasty)
Acquire Trade Cards - Players draw a trade card for each city they have.
Trade - The meat of the game. Players trade Trade cards to get sets, which are more valuable than individual cards.
Acquire Civilization Cards - Sets gained in trade are exchanged for Civilization cards. These cards are worth points and indicate how civilized your country is becoming. They also benefit your country in various ways. For example, Astronomy allows ships to cross open sea instead of having to hug the coastline.
Resolve Calamities - Calamity cards are hidden in the trade stacks. These can be passed to other players during trade, unless they have red backs. Calamities are enacted in order and usually cause woe to the civilization they affect.
Move on AST - Each players token is moved forward on the AST, unless conditions to pass certain points have not been met.

Play continues in this way until a player reaches the last space on the AST.

As you can see, in the opening game, most of these phases aren't used, but once trading begins, most of the phases are then in use. Although there are only 15 spaces on the AST, it usually takes much more than 15 turns to travel along it. Each turn then lengthens into a half hour or more, especially when all seven players are playing.

Avalon Hill took another look at the game and a few years later, they produced Advanced Civilization, an expansion for the original. New victory conditions were introduced, which could let the game be played in an evening. Rules for eight player games, just in case seven wasn't enough. Extra attributes for Civilization cards, simplified trade rules which speed play. All in all, it was a welcome addition.

SUMMARY:
If you can get hold of a copy of this game, then its a must to add to your collection, even if you only get hold of the original Avalon Hill version. It's an excellent way to spend a few hours of quality gaming time. Recommended. Review by Brian