“Sahel: Art and Empires on the Shores of the Sahara,” which opens on Jan. 30 at the Met, tells the epic story of a network of African cultures that flourished, from the fourth century through the nineteenth, in the vast region that now encompasses Mali, Mauritania, Niger, and Senegal. Among the two hundred treasures on view—in wood, stone, gold, ceramic, bronze, cloth, and more—are the magnificent figures pictured above, of a mother and child and a man with a turned head, both made by the Bamana people of Mali.