From a little clearing he could suddenly see downstream. The flood in spate had torn the Little canyon clear. Everything that had been down there before— Beach Road, the small bridges and buildings, the ranger station, the picnic areas—all of it was gone, leaving a raw zone of bare sandstone, flat mud, thrashed grass, downed timber, and stubborn trees that were either clinging to life or dead in place. Many trees had been knocked over and yet held on by a few roots, forming living snags piled high with mud and trash. A larger snag downstream looked like a giant beaver dam, creating a dirt-brown pond.

The sky stood big and blue overhead, a tall dome that seemed to rise as the day lightened. Muddy Rock Creek burbled noisily down its course, spilling from one foamy brown stretch to the next.

At the far edge of the pond a heron stepped, its knees bending backward. Long body, long legs, long neck, long head, long beak. A great blue heron, Frank guessed, though this one’s dark gray feathers looked more green than blue. A kind of dinosaur. And indeed nothing could have looked more pterodactylic. Two hundred million years.

Sunlight blazed green at the tops of the trees across the ravine. Frank and the heron stood attentively, listening to unseen smaller birds whose wild twittering now filled the air. The heron’s head cocked to one side. For a time everything was as still as bronze.

Then beyond the twittering came a different sound, fluid and clear, rising like a siren, like a hook in the flesh:

Oooooooooooooooooop!

National Science Foundation, Arlington, Virginia, basement parking lot, seven a.m. A primate sitting in his car, thinking things over. As one of the editors of The Journal of Sociobiology, Frank was very much aware of the origins of their species. The third chimp, as Diamond had put it. Now he thought: chimps sleep outdoors. Bonobos sleep outdoors.