I found particularly interesting Connah's description of the West African coast as protected from outside intrusion because of its mangrove swamps, lack of natural harbors and prevailing winds -- until the middle of the fifteenth century when the lateen sails and stern-post rudder of the Portuguese caravel allowed European explorers to sail into the wind. Prosperous cities sprang up along the east coast of Africa, on the other hand, because the wind and currents of the Indian Ocean change direction twice a year, fostering commercial and cultural interchanges with India and Indonesia that began in antiquity. I was also struck by Connah's observation that the sickle-cell gene (associated with anemia among American blacks) once functioned as partial protection from malaria in the West African forest.

Connah succinctly reviews the scholarly hypotheses about the decline of Great Zimbabwe (which may also be relevant to the decline of Mayan culture). The massive fortress wall of this city, dating from the 11th century A.D., is the biggest stone structure in sub-Saharan Africa. At its peak, Great Zimbabwe's population may have exceeded 10,000. The city did not fall by enemy attack or European interference but probably through the exhaustion of its own environment: firewood was used up, game depleted, fields overgrazed and soils over-cultivated.

Although the elevated Zimbabwe Plateau was largely free from the tsetse fly, which afflicts both human beings and livestock, a sanitation crisis may have been created by the large, dense urban population. Sewage breeds disease, contaminating the water supply and threatening public health in expanding societies. This squalid, putrid, intractable problem has been solved outside the Third World by the miracle of modern plumbing, the gift of Western capitalism and the industrial revolution, at which our pampered, armchair leftists like to sneer. A sign should be posted over every campus toilet: "This flush comes to you by courtesy of capitalism."

Now for our usual pop finale. I won't deal with football, since I'm still crabby over the low level of play in last weekend's championship games. A top TV moment of the past month for me was Lifetime cable channel's "Intimate Portrait" profile of Deidre Hall, the blonde diva of NBC's daytime soap, "Days of Our Lives." Eerily ageless, Hall still exudes the composure, magnetism and aloof sexual mystery that have characterized her performance as glamorous Dr. Marlena Evans since 1976.

There was a radiant womanliness about Hall's persona at her popular height that I often meditated on while writing "Sexual Personae." This serene, centered quality, seen in "women's picture" stars of old Hollywood like Lana Turner and still detectable in the 1970s and '80s in actresses Jaclyn Smith and Anne Archer, is now tragically missing from contemporary pop culture with its jittery anorectics ("Ally McBeal") and compulsive, sarcastic mantraps ("Sex and the City"). Enduring artistic work is unlikely to come from the bitter sexual wasteland of current pop, where androgyny is just an excuse for protracted adolescence.

As for film, the laurel goes to Turner Classic Movies cable channel for last week's sensational double feature: Bette Davis impassively shooting her way down the front steps of a moonlit rubber plantation in William Wyler's "The Letter" (1940), followed by Marlene Dietrich in a blonde Afro uncoiling herself from a gorilla suit to sing "Hot Voodoo" backed by a gaggle of bopping tribal chorines in Josef von Sternberg's "Blonde Venus" (1932).

When Dietrich in gleaming white top hat and tails saucily sashays down the ramp of a Paris cabaret, she gives a stunning, point-by-point lesson in how to "work" a costume and maximize a prop (a long cigarette holder) -- fundamentals our brat pack of current A-list stars don't have a clue about. We'll see whether Dietrich's leading admirer, Madonna (whom Dietrich called "vulgar"), having cleverly married her own junior-league von Sternberg, will ever match Dietrich's elegant yet empathic mastery of the silver screen.

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