It has the following modifiers:
+1per city
10%in capital
10%overall
For the first 2/3rds of the prehistoric era, your entire science output IS your capital and the +1 at the time you get choose the first trait is pretty much 10% in itself
Still, even ignoring that +1 you are looking at a 21% (1.10 x 1.10 = 1.21) increase in science.
And I don't know the AI's preferences, but most players will make getting animal myths and elder council a priority so the whole thing snowballs quite quickly
The thing is, the traits as they are now aren't really designed for the cultural upgrade system. A separate trait system was being implemented whereby, each trait had a level, lvl 1, 2, 3 scientific. Level 1 would be much less powerful a version of the trait (designed specifically for early game).
I got about half way through implementing this and it grew tiresome and time consuming, I still plan on finishing it (soon

I personally don't play with that option on, the traits you choose, you choose from start to finish depending on the leader for me. I haven't played much scientific so, what im trying to say is - your probably right..
