Which of the following was a direct cause of job specialization in early human civilizations.
a. development of agriculture
b. stratification of society
c. establishment of trades networks
d. improvement of hunting methods

The best option regarding a direct cause of job specialization in early human civilizations would be "a. Development of agriculture," since this meant that there was a surplus of food--meaning that people could focus on things other than obtaining and growing food. 

Independent executive agencies are more specialised.