Left-most Technologies (Cataphract, Archer, Cavalry, Feudalism, Monotheism, Science, Catapult, Galley, Mint, and Warrior) are base tech. You start with them. You may research one new technology every turn. You must have all technologies leading to a technology to have it (e.g. to get Raider, you need Galley, Warrior and Longship). Time taken to complete a concept technology/unit technology/building technology: highlighted by tech boldness (bold: 3 years/15 IRL days, very bold: 6 years/30 IRL days/~1 IRL month, black outline: 9 years/45 IRL days/~1 1/2 IRL months)
As the new tech admin (and kind of being lost rn), I adjusted the research times for tech. Now it takes longer to get to renaissance, and a little longer to get the tech after it. I hope I didn't ruin any RP progressions after this