The wide area of dry land that borders the southern edge of the Sahara.
Explanation:
a )they help historians focus on the effect of one important idea on different societies over time
<h2>Answer</h2><h3>The caste system originated in our society depending upon the type of work and the nature of persons. This has reflected as class system in many other societies. However the caste system in the course of time became hereditary irrespective of one’s nature and the type of work a person undertakes.</h3>
