There are great websites out there that can give you the history of commercial illustration with facts and figures. What I’m going to do is break business art and design down according to the key points that pertain to how human beings understand imagery.
Here it goes:
People gather in communities, creating the need for communication.
History gains context as generations pass and the need for written communication develops.
Illustration becomes primal and necessary.
A long time passes, and some really smart people invent the written language.
Written language can only be understood by the wealthy, while the lower class keeps a hold of illustration.
Since the few are wealthy and the many are poor, the wealthy still use illustration to communicate with the masses (think cathedrals, statues, ceramics, etc.).
The Industrial Revolution happens, and within a hop, skip, and a jump, we have access to printed text, mass literacy, and centralized communication processes.