updated main post to here
Yea, I have -1 STR as a fisher and scavenger/toolmaker mainly.
No other skill ups so far.
Scavanging - Intelligence
Had a status change last night while scavanging.
I got a point of intelligence from arch, although I think the majority of it was from scavenging, but the actual stat increase was during arch.
I got perception while woodcrafting, although I probably got the majority of the point from Scavenging I had recently done. Also got a Dexterity point while woodcrafting
The chart in the "manual" shows which stats are Primary and Secondary for each skill. So, broadly speaking, if you use spend a lot of time using a particular skill, the Primary and/or Secondary stat for that skill will increase.
I've spent 95% of my time Scavenging (98), Foraging (98), Tailoring (64) and Leathercrafting (82). I've gained +2 Perception, +1 Dex, +1 Intelligence and lost 2 Strength and 1 Spirit. I expect either Strength or Spirit to drop another point soon, seeing as I'm still doing the same activities. The increased stats are all associated with the skills I've been using.
The mystery is which stats are chosen to decrease, and why...
5k+ Bricks got me 80 masonry and i have 95 Terraforming, so far -1 cha -1 spirit.