It’s introduced by two sculptures that are among the oldest on view and feel monumental in very different ways. A seven-foot-tall megalith, dating from the 8th- 9th century A.D. is by far the show’s largest work. But with its russet surface and plump V shape it has a hunkering delicacy. The second sculpture is much older — pre-2000 B.C. — small: pebble-size. But with a few lightly incised tweaks a resourceful artist has conjured an icon of procreative female power.

What the intended meaning or ritual use of these objects actually was, we don’t know. But they provide a baseline of antiquity for the curators to build a history on. And so they do, plotting it almost diagrammatically, by dates and themes, in two rows of mini-galleries with a wide path between. And they line the path with a kind of honor guard of a dozen equestrian sculptures in terra-cotta, metal and wood.

The cavalcade is a beautiful idea. The images, produced over a wide time span, from the 3rd and 19th centuries, by cultures in present-day Mali and Niger, are widely varied in media, style and probably function, but lined up together they suggest a kind of symbolic solidarity, an affirmation of the integrity and complexity, past and present, of something called the Sahel.

A major invasive event during that time span was the coming of Islam, which hit the Sahel shores in the 7th century, and stayed, and spread. Because Islam introduced literacy, it had pervasive and subversive impact. But, maybe in an effort to correct an old view that Islam was responsible for Sahel culture’s vitality, neither it nor any other outside trans-Saharan force is given a center stage in the show.