today I played a 9 random godlike AI immense map and thought I am in rather good shape, a few turns later (171) I was greeted by the "defeat" screen.
My first suggestion is that when you lose a game - let us know who won the game! I had to dig into the replay and take over the AIs (localplayer #) to see that it was a science victory by the Torians (not 100% sure).
One thing I realised in this game: You need less science to research your techs when you avoid meeting other species. The Torian guy just knew 4 other species and had 2k science output (17 planets). Can you verify that?
I attached the save/metaverse-link if anybody is interested (there were 2 custom races).