The pendulum needs to swing back to find the actual divisions that separate us from them and better understand what it means to be human. We separated from a common ancestor with chimpanzees at least 5 million years ago, and random mutation coupled with the evolutionary forces of positive and negative selection have steadily driven the two species further and further apart. For starters, we have 46 chromosomes and they have 48. A recent comparison of chimp and human genomes that assesses all our DNA, including the vast majority that does not make up protein-coding genes but has a major influence on their function, finds about a 5 percent difference—more than a four-fold difference from what was previously thought. Many diseases that profoundly alter our lives—including Alzheimer's—have no impact on them. (Note to Rodman: lousy animal model.) Only humans primarily walk upright, cook, teach, swim, miscarry at high rates, run long distances, and depend heavily on grandmothers to raise children. Chimps have remarkable short-term memory that may outperform our own, and, as Rise of the Planet of the Apes repeatedly emphasizes, jump and climb with a power and grace that put Cirque du Soleil acrobats to shame. Side-by-side analyses of autopsied brains from chimpanzees and humans further reveal distinct architecture and gene networks in each species.
Language is one of our most pronounced differences. Chimpanzees and other nonhuman great apes communicate in sophisticated ways, and researchers working with the likes of Nim have shown that they can learn to use signs and symbols to speak with humans. But Project Nim, led by Columbia University psychologist Herbert Terrace, marked a watershed moment in ape language research—and effectively killed the high-profile field.
Documentary maker James Marsh ( Man on Wire) goes to some length to pillory Terrace for showboating and treating both humans and Nim callously, which oddly garbles the main import of his groundbreaking language research. In a devastating paper published in Science in 1979, Terrace and his co-workers asked, "Can an Ape Create A Sentence?" They analyzed more than 19,000 utterances of Nim and determined, convincingly, that their subject—along with other famous signing apes, Koko the gorilla and Washoe the chimp—had fooled researchers. Upon close inspection, Terrace's group decided that the apes were stringing words together in response to the recent signs of their teachers and, for the most part, were making simple demands. "Apes can learn many isolated symbols (as can dogs, horses, and other nonhuman species), but they show no unequivocal evidence of mastering the conversational, semantic, or syntactic organization of language," they concluded.
In the 32 years since, no one has proven Terrace wrong. Critics of the work with Nim rightly point out that Terrace and his slapdash crew of students had methodological problems with their experiment, and legitimate debates exist about the meaning of "language." But no compelling evidence has come forward that any apes, other than humans, can acquire massive vocabularies (we typically have 60,000 words by high-school age), use words with a set of rules, embed several ideas in a sentence, or converse with a humanish give-and-take of speaking, listening, and responding. Linguist Noam Chomsky, Nim's namesake, was right. Humans, and not chimps or gorillas or bonobos, seem hard-wired for language.
One of the most telling language differences between us and them comes from the researchers who claim to have made the most progress teaching apes to communicate. In an eyebrow-raising gambit, Sue Savage-Rumbaugh in 2007 co-authored a scientific paper with three bonobos. She spoke with her colleagues using symbols called lexigrams and vocalizations. The study, "Welfare of Apes in Captive Environments," recounts how Savage-Rumbaugh had a dialog with Panbanisha, Kanzi, and Nyota about what they need. She proposed various options and asked them yes/no questions. The 12 they deemed important—which include the ability to move and interact with others at their choosing, fresh food that they like, and freedom from fear of harm by humans—hardly surprise.
What if the design of the experiment actually asked the bonobos what they needed? These bonobos routinely go on walks in the woods near the sanctuary that houses them in Des Moines, Iowa. Their handlers restrain them with collars and leashes. Imagine if Panbanisha said, "To run free without a collar and leash, which demeans me and makes me feel like a pet." Now we're talking language, crossing the Rubicon, and being forced to reconsider where to place the line that separates Julius from Caesar, Noam from Nim. But of course none of them said anything of the sort.