Gaia is always right under our noses. It is the "player" humming in the background; governing trees, animals, and mines. However, thanks to the "natural wonders" cheat, I have been able to dissect some little known details about Gaia. One thing that really caught my eye was its unique tech tree.

Gaia seems to have a full tech tree, with huge gaps and exceptions in the dark age. It is impossible to get out of the dark age with Gaia without editor intervention, since the only buildings that Gaia can build in the dark age are Barracks, houses, and outposts.

Dark Age-------------

Buildings
Barracks
Outposts
House
Farm (only if you have dock)
Unavailable: Dock, Mining Camp, Lumber Camp, Mill, Palisade Wall

Units
*none*
Unavailable: Militia, villager

Technologies
Loom

Feudal Age------------
Buildings
Archery Range
Stables
Blacksmith
Market
Stone Wall
Watch Tower

Units
Upgrade Militia to MAA (in lieu, has no effect)
All other units

Technologies
All techs

From then on, Gaia gets all technologies and buildings and units. However, they get no unique unit or unique technology. From the Castle they can still build trebuchets and petards and research all the techs there. Note, however, that spies has no effect for Gaia.

Note also, that Gaia can create units and research technologies at buildings they can't build (they get all mining, wood chopping, etc. techs) and those buildings are fully functional. They never get staple infantry (due to the lack of Militia, though they get all upgrades till champion, they have nothing to upgrade). Also, when a Gaia unit is created or a building is built, instead of... lets say "---Paladin Created---" as a message you get at the bottom of your screen, you get instead "---(null)Created---." This applies to buildings, too. Technologies, however, are displayed properly.

Concerning Farms:
Gaia farms start out with 0 food, but food can still be collected. When a Gaia villager is farming a Gaia farm, the food counter on the farm will go into the negatives as the farm is farmed. In essence, gaia farms have infinite food. If a player 1 unit comes by, the farm will convert to player 1 and have the food collected by the Gaia villager deducted from the farm (farms start at 175 food)
ex: Gaia farm has -110 food, player 1 captures it, then the farm has 175-110= 65 food left. If the Gaia villager farms more than 175 food, then when the farm is captured, it simply has 175 food. I think that farm upgrades apply.

Another intresting fact: No matter in the editor what Civilization you set Gaia, it will not speak the civilization's language. Nor will it speak Arabic (it is default set at Saracen). Actaully, I dont know what language it speaks. Anyone who wishes to help will be much appreciated.

Also, Gaia units cannot garrison. Villagers even ignore the town bell. However, if you task the unit to garrison into its creation building, it will as usual.