Answer
A. Development of agriculture
The direct cause of job specialization in early human civilizations was Development of agriculture.
Step-by-step explanation
-Job specialization was a process where focus was on ones occupational concentration on where people had most experience in.
-If it increases in high levels among the employees it may make them to be less flexible since it may reduce their ability to perform other types of work within the duties.
-It was sometimes called division of labor because because organisations divided individual tasks into separate groups. This allowed for people to specialize in one area of focus and trade their goods..