Unfortunately, since the river tribes that knew the secret were all wiped out by European raiding parties 500 years ago, the scientist must start from scratch. He knew he wanted to do fieldwork when he studied primates in Holland. There Van Roosmalen clashed with his university professors over the value of observing lab monkeys. He spent years in Suriname, studying spider monkeys in their arboreal home. Often he survived on fruit gnawed by monkeys and then tossed away.
Spider monkeys are very economical eaters.
On the strength of doctoral research into tropical ecology, Van Roosmalen in 1987 got a scientific post in Manaus with the Brazilian government. Inside the rain forest, Van Roosmalen is an ethereal presence with his long, silvery-blond hair. He ghosts through the foliage, hardly stirring a leaf. There's the sudden drum of raindrops shaken off a tree high in the canopy, and Van Roosmalen trains his binoculars upward. A branch bounces, and out pops a Titi monkey with black, globed eyes and a pewter-colored beard.