I think this one will tougher to beat.
I almost tossed this one out. I moved to the BG and settled there once I saw it was coastal.
Barbarians: NONE.
Climate: NORMAL.
LandForm: ARCHIPELAGO.
Map Size: STANDARD.
Ocean Coverage: 80%.
Temperature: TEMPERATE.
World Age: 5 BILLION YEARS.
Aggression: Less Aggressive.
PLAYERS:
Babylon (Human player)
Greece
Korea
Hittites
India
My starting builts were warrior, worker, temple, settler, colossus. It turned out I was on an island of my own. Even with the slow start due to 20K, I was able to settle most of the island, including 3 Ivory, 3 Silks, 1 horse, and 2 Iron.
My research was Masonry, Alpha, Writing, Lit, CoL, Philo, Republic (free). With two Sci civs, I was cafeful not to trade Writing until someone already knew it. This time I didn't gift anyone a bunch of techs to advance them into the next age. I waited until they were down to their last tech and I needed to renew some lux or gpt deal. So, I didn't gain much research help as I could have.
My MA research was to head for Bach and then Shakespeare. Then Astronomy, Eco and Nav before doing the bottom. By that time, a couple civs where up to the MA. I picked up engineering and gunpowder.
Once I got Navigation, I sent out ships and settlers to grab some of the isolated, unclaimed islands. My first game, reminded me of the importance of grabbing as much territory as possible for those late game resources. I picked up oil, aluminium and uranium that way. I was a little slow on one island and picked the wrong spot, just missing rubber. I tried roading it for the Hitties but they traded it away, so I never got any.
Luckily, I didn't need it. The other civs were always half an age behind me. The only aggression I faced was from India with MI and Cav parties landing occasionally. They were easily dispatched with Arty, Knight/Cav and the odd Rifleman.
My IA research was Steam, Ind, Corp, then to RP and ToE. I researched Refining and Steal and timed ToE to grab Atomic Theory and Electronics. Avoiding a wonder gab in the IA is pretty tough on Emperor.
My free techs were Fuedalism, Nationalism, and Fission.
I reached 20K in
1550AD!

I don't doubt someone will be able to post an impossibly better date, but they are going to have to work at it.
I had tremendous SGL luck! I got 2 in the AA and 2 in early the MA. I had a lot of tough decisions due to timing. Whether to rush a half built wonder or wait. It may not be correct, I always chose to delay. It seems to me that long term, tossing out a couple hundred shields isn't worth getting that one wonder's culture a little earlier. I also chose to delay building the GLib, which I could have built instead of Pryaminds, but that would have given me despotic GA. Luckily, the SGL came along and let me make up some of that.
Here are my cultural builds: