Crossing Over: Where Art and Science Meet (Crown, $27.50) is a collection of essays by Stephen Jay Gould and photographs by Rosamund Wolff Purcell which aims to present science and art in conversation. In this context, a gibbon and Fred Astaire — “brothers under the hair” — are juxtaposed, and a tin toy illustrates the role of bilateral symmetry in creating complexity. The fossil ammonite shown above, cut, polished and set against a slab of jade, is a symbol of the arbitrariness of extinction and survival — ammonites survived two major mass extinctions, only to succumb to the catastrophe that obliterated the dinosaurs.