The tech tree from early access builds Techs (short for "technologies") are empire upgrades that cost science and provide various benefits and make additional techs and some laws and events available.
Tier 1 (80 Science)
Technology
Prerequisites
Effects
Ironworking
None
Stonecutting
None
Trapping
None
Divination
None
Administration
None
Tier 2 (120 Science)
Technology
Prerequisites
Effects
Labor Force
Ironworking
Husbandry
Ironworking
Drama
Stonecutting
Polis
Stonecutting, Trapping
Trapping
Military Drill
Aristrocracy
Divination
Sovereignty
Divination, Administration
Rhetoric
Administration
Tier 3 (200 Science)
Technology
Prerequisites
Effects
Navigation
Labor Force
Phalanx
Labor Force
The Wheel
Husbandry
Ramparts
Drama
Forestry
Polis
Battleline
Military Drill, Ironworking
Monasticism
Aristocracy
Composite Bow
Rhetoric
Metaphysics
Rhetoric
Tier 4 (400 Science)
Technology
Prerequisites
Effects
Citizenship
Phalanx
Drawbridge
Ramparts
Land Consolidation
Forestry
Steel
Forestry, Battleline
Doctrine
Monasticism, Metaphysics
Siegecraft
Sovereignty
Tier 5 (800 Science) Coinage
Scholarship
Torsion
Stirrups
Architecture
Manor
Machinery
Mounted Archery
Cartography Tier 6 (1600 Science) Hydraulics
Lateen Sail
Warrior Code
Bodkin Arrow
Aesthetics
Unit Tactics
Strategy Tier 7 (3200 Science) Vaulting
Jurisprudence
Barding
Sarissa
Fiscal Policy
Windlass Tier 8 (6400 Science) Economic Reform
Military Reform
Political Reform 