Inspired by the question What technologies could an every-man teach a Palaeolithic tribe?
If you want to jump start the civilization of a late paleolithic tribe, and instead of high school dropout you can send one skilled tradesman or professional. What kind of tradesman / professional would do the best job?
The constraint is that person should have excellent current knowledge of their own trade or profession, plus some knowledge of related trades/professions. All the other knowledge comes just from watching TV & reading web sites or magazines.
For example if you choose geologist, they would probably know about where to find ores, have some idea about metallurgy, but don't know anything about agriculture.
If you choose surgeon, they would know a lot about human body, maybe basics about herbs.
Note that (s)he time travels in the past without any useful tools or materials. They will have to rebuild everything from scratch. The only tools available are made of stone and wood. The tribe has fire, wooden spears, primitive sewing tools, hooks and that's pretty much it.
The time traveler is transported back in time in the same place where they live. For example if they are from Barcelona, they would be transported back in Barcelona in the paleolithic.
There are no domesticated plants nor animals, not even dogs. Bow hasn't been invented. The tribe subsists on hunting, fishing & gathering. The tribe is semi nomadic, thus moving seasonally from place to place according to traditional route. The tribe leaves on the shore, on the continent. The climate is temperate with 4 seasons.
The time traveler is accepted as fellow tribe member, thus they will help him/her with his/her silly ideas, after (s)he does his/her share of work. The more immediately useful the inventions are, the more help they'll be able to get.