I am playing a game at the moment, I started on Prince... and got SLAMMED!!
Here is a summary ... start the game up, play about 20~40 turns...
Lauxcaus Paints have been built in a far away land (HBBIAFAL, from now on...)
Wow... I had only just researched the techs to get that building... scary. Oh well... continue playing... and soon enough
Skara Brae HBBIAFAL
WTH!? Seriously man... I am still 4 techs away, and I almost bee-lined it. That just... sucks. Someone had an insane commercial start... Play for a few more turns, and...
Augustus Ceaser is the first to discover Sedintary Lifestyle!
HOLY CRUD!! The year is
74000 BC I haven't even got 3/4 of the way there... Sedentary Lifestyle is still 9 techs away for me!
I am going to restart at Noble Difficulty, but what bonuses have you given the AI? They seem to start with Slingers, and at least 2 other units, and also seem to get Fletching, and Cave Painting unusually early. So what free techs and units do they get?
Finally, do Seed Camps obsolete? As they are, they are superiour to farms, so you will have to either weaken them somehow, or possibly make them obsolete later (-1

with Agriculture, -1

with Construction). Mines / Stone Tool Workshops are better (You are exchanging hammers for commerce), and it wouldn't be too bad if they lasted beyond mining (which I think they do), possibly all the way to Iron Working...
Lumber-mills (The early-game ones) need to be almost instant to be built, as it is pointless building Lumber-mills on any tile without ceder... its better (after Bronze Working) to cut them down, and get a burst of hammers, and a better improvement.
If you don't like having instant improvements, maybe giving them +1 hammer, and +1 commerce would be better? Or maybe +1 food, +1 hammer...? +2 hammers?
I don't see a point having a Lumber-mill to be honest... it is rather weak...