Prior to farming and animal domestication, people did not specialize. They couldn't. To survive, they had to hunt, gather and forage for themselves and their family. This required both generalized knowledge and an extraordinary amount of time and energy.

It wasn't until humans began farming and domesticating animals that a single person was able to produce food for hundreds of other people. This allowed those who weren't doing the farming to focus their attention elsewhere. With time, this led to specialization in subjects like medicine, war, art, construction and so on.

The farmer allows the doctor to doctor. The doctor allows the accountant to account. The accountant allows the builder to build. If you want to create tremendous value within an organization, specialize. Specialization spawns specialization.