Ndokanda, a bangombe pygmy, hunkers down beside me. Holding the bridge of his nose, he lets out a loud bray -- his dead-on imitation of the cry of small rain-forest animals called duikers. These deerlike creatures make the noise in the throes of giving birth, and Pygmies imitate it because other duikers come running when they hear the call. This time, however, the braying attracts a large band of chimpanzees, drawn by the prospect of dining on vulnerable duikers. For a moment I feel the shiver of being hunted.
But when the chimps spot the Pygmy and his three white companions, the animals stop dead in their tracks. Their bloodlust gives way to astonishment, as if they are seeing something they have never seen before. They begin stamping their feet, shaking their arms, calling to one another and throwing branches at us. As many as 25 animals scream from all sides. Each time we make a move, a new round of calls erupts among the chimps, but they never show signs of fleeing.
Instead, for more than two hours, the mesmerized chimps hover around us, drawing to within a few arm lengths. I am flabbergasted. Wild chimps do not react this way to humans in any other part of the African rain forest. But this is no ordinary meeting of fellow primates. For the chimps surrounding us, seeing humans amounts to an ape version of Close Encounters of the Third Kind.
In this drama, we are the aliens. We have ventured into the last vast unexplored rain forest on earth -- the unsullied Ndoki region of northern Congo -- a place where the animals do not know what to make of us because they have never seen humans before.
The word Ndoki (pronounced en-doe-key) means "sorcerer" in Lingala, and this is indeed an enchanted, mysterious place. Guarded by swamps to the south and east, hills to the north and the forbidding Ndoki River to the west, the region is almost inaccessible. Pygmies have crisscrossed central Africa for thousands of years, but there is no evidence that they have entered beyond the fringes of this 3 million-hectare (7.5 million-acre) expanse of virgin forest, which is about the size of Belgium.
Our 15-day expedition, led by botanist Michael Fay of Wildlife Conservation International, has taken us to parts of the forest we believe no human has ever seen. We are catching a glimpse of the rarest treasure on this crowded planet: an ecosystem as pristine today as it was 12,000 years ago, before humans began to transform the earth. Our journey into unknown territory is a grand adventure, one that is as exciting as it is daunting. At one point, Fay must persuade apprehensive Pygmy trackers to continue through the Ndoki, for legend holds that the forest is home to Mokele Mbembe, a dinosaur-like creature that can kill elephants.
Mokele Mbembe could hardly create more of a stir than we do in this previously undisturbed land. Gorillas stare and scream at us, and sometimes charge, but almost never run away. Colobus and cercopithecus monkeys crane their necks to eye us from high tree branches. Gloriously fat wild pigs, elsewhere the favorite game of hunters, look up from their rooting and peer at us calmly through the low brush for several minutes before moving off toward new forage.