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The first scientist to see the Bili apes was Shelly Williams, an independent primatologist who visited the region at Ammann's invitation in the summers of 2002 and 2003. She says she documented separate groups of East and West African chimpanzee subspecies and what she calls the "mystery ape." The larger animal had a much flatter face and straight-across brow like gorillas and turned gray early in life. Females lacked chimps' genital swelling. Two or three would nest on the ground, with others low in nearby branches. They made a distinct vocalization like a howl and were louder when the full moon rose and set. "The unique characteristics they exhibit just don't fit into the other groups of great apes," says Williams. The apes, she argues, could be a new species unknown to science, a new subspecies of chimpanzee or a hybrid of the gorilla and the chimp. "At the very least, we have a unique, isolated chimp culture that's unlike any that's been studied," she says.
That last, least dramatic theory is the one preferred by most scientists who have visited the region, including Harvard ape expert Richard Wrangham, who thinks the ground nests are built by chimps looking to escape dampness during the day. When Hicks and Ammann describe the animal they are studying, they use "mystery ape" only with irony. Ammann is worried that Williams' sensational pronouncements have brought ridicule to his project. "If there's scientific data, that's one thing," he says. "But basing all of this on anecdotal stuff ..." Recently, he was emailed pictures of a chimp with a pug-dog's head and a seal sprouting a gorilla's face. "Clearly, someone thinks we're a joke," he says. An analysis of hairs found in the ground nests identified their mitochondrial DNA (mtDNA) as East African chimpanzee. Williams counters that finding with three arguments: the DNA could have been contaminated, the use of human genetic markers might mask hidden differences, and mtDNA would not show variation in the paternal line. "Until we know the father's lineage, we can't say if it's a new species or not," Williams insists. No longer welcome in Ammann's camp, she says she will return to the area in March to set up her own project.
"I think people are going to be disappointed with the yeti in the forest," warns Hicks, who says the apes he has seen are clearly chimps, although some are strangely oversize. "The evidence doesn't point to [a new species]. I think what needs to be focused on is the cultural differences." In addition to building ground nests, the apes fish for ants with tools that are several times longer than those used by known chimp populations. For now, Hicks is concentrating on habituating the animals, getting them accustomed to the noisy, nosy presence of researchers. The science--and the videotapes--will come later.
"Genetically, they're not even a subspecies," says Hicks. "But behaviorally, we may be seeing the beginning of a departure from chimpanzee norms. We could actually be catching evolution in the act. That is, if they're allowed to survive."