This is known as "specialization of labor" and, when left to settle appropriately, will do so even if there is a 51/49 split of efficiency.
So that you can evaluate cases such as you have a fisherman and lumberjack. If the fisherman needs wood is it better for him to spend an hour gathering the wood himself or spend and hour fishing and then trade some fish to the lumberjack for the wood.
Incidentally, this is really the genesis of the gender split between work outside the home and inside the home. When most "work" was physically intensive and there was more domestic demand (i.e. before microwaves, easy-prep bag meals, etc.) the slight bias in the abilities of the genders made it more efficient as a household unit to have the wife stay at home full time. Starting with modern home conveniences in the 60s and a less physical, service-based industry in the 70s, only then were you able to see those roles mix. Of course, the result wasn't that the man was staying at home a higher percentage, but rather that the woman could create a 2nd income.
This is also the reason that it was more efficient for people to live in groups. Any variance in the skill (either capability or learned) tipped towards specialization. The unit as a whole was more productive when people simply focussed on what they were good at. Add in the homo economicus model of every person trying to improve his or her situation (a la Adam Smith) and a cooperative competition balance is struck (a la John Nash). The "invisible hand" that Adam Smith writes of is sometimes mis-cast as a central planner when, in fact, it is actually the emergent behavior of the economy as a whole that arises out of the individual rationally economic actions. It is THIS idea that the OP is trying to model.