Why did Saharan post-Pleistocene populations adopt agriculture?

Why did Saharan post-Pleistocene populations adopt agriculture?

Studies of !Kung, San revealed that their subsistence base (hunting and gathering) was surprisingly abundant and predictable. Although they had to make subsistence efforts throughout the year, the Khoisan enjoyed considerable leisure. M. D. Sahlins has been inspired to label the Paleolithic as the original affluent society (1968:85).