Looking for a strategic game that encourages diplomacy and economic behaviour, you should look into Erectus.
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Closed Beta Keys
The publisher is giving away keys for the closed beta via mmogames.com
The name Erectus is taken from Homo erectus, the ancestor of modern man. Both human races want their space to live and became enemies in Erectus the Game. Players take on the role of Homo sapiens and build their empires with the end goal of defeating the Homo erectus armies. The story takes place 130,000 years ago and allows players to form alliances and unite against the common enemy as well as against each other.
Players’ success will rely heavily on their strategic, economic and diplomatic management skills. As the game world shifts, players will have to quickly adapt their strategies and successfully micromanage their empire in order to expand and achieve greatness.