Are we just smarter Chimpanzees, who have managed to master language and fire, and lost our hair? Or are we more like Bonobos (formerly called Pygmy Chimpanzees), or another of the great apes? Or are we wholly unique?
For all the "monkey acts" and movie chimps, very, very few people have seen a mature chimpanzee, on film or face to face. The cute performers that everybody loves are all little more than toddlers. By the time they are eight or nine years old they are much too dangerous to appear with human actors. While the "common wisdom" that an adult male chimp is five times as strong as a human is overblown, the fact is that the average chimp is twice as strong as a well-conditioned human body-builder (Y'know, I'm not well-conditioned, so the chimp probably is five times as strong as I am!).
Also, the notion that chimps, or any of the great apes, are a "good" model animal for the ape progenitor of hominids is simply wrong-headed. Since the hominid line split from the common ancestor that also led to chimps and bonobos, the humans and the chimps have both evolved similar amounts. Call our common ancestor George. Tarzan's pal Cheetah is as different from George as Tarzan is, or we are.
Since Robert Yerkes published Almost Human in 1925, it has become fashionable to humanize chimps. In the view of many we are some mix of unstable, violent, patriarchal chimpanzee and conciliatory, sexy, matriarchal bonobo (the "hippie chimp"). It is simply rampant confusion. Amidst it all, science writer Jon Cohen undertook to find out what is the same, and what is different, about chimpanzees and humans. Because there is so much written about similarities, he chose to lean toward the differences, though he was warned to "be careful" by more than one researcher in the field.
The result of his travels and interviews and investigations is Almost Chimpanzee: Searching for What Makes Us Human, in Rainforests, Labs, Sanctuaries, and Zoos. Throughout the book's twelve chapters, the differences abound. Starting with a possible hybridization episode about five million years ago, genetic differences have accumulated, leading to different markers on our blood (and body) cells, different responses to viruses, and certain markedly different biochemical patterns: a human would starve on a chimp diet of 5-7 kilos of raw leaves and fruits daily and only 1-2% of calories from meat.
While it may be possible for any of the great apes to hybridize, because all have 48 chromosomes, humans have only 46, making hybridization next to impossible. A Russian named Ivanov tried to breed a humanzee, but failed. Our chromosome 2 is cobbled together from 90% of the 12th and 90% of the 13th ape chromosomes, appended end to end. The missing 10% of each has no function yet known, but something is surely missing.
Of course, what people most want to know is how apes think. Efforts to teach them to speak, or use sign language, or use symbolic languages such as Yerkish, have gone on for a century or more. I remember reading a touching article by a deaf woman who reported meeting Koko, the gorilla who knows sign language: "I was communicating with another species in my mother tongue!" Since the longest "sentence" Koko has used is three words ("you tickle Koko"), it must have been a rather limited "conversation". No discussion of Plato or the meaning of existence. The most level-headed researchers seem to have all concluded, a chimp really lives a day-to-day existence. There just isn't much to learn from talking to one. You can exhaust their cognitive repertoire in a half hour or so.
The other thing many people want to know (but are afraid to ask) is how sexy are they, really? A chapter on penis size and sexual habits debunks the notion that ape penises are tiny. The average "hang" for chimp and for human is almost exactly the same, but the testicles differ greatly, because of those "habits". When receptive females are available, a dominant male chimp might have intercourse five to eight times a day, for day after day. Most human males run dry after three days of twice a day (some persistent hedonists might be able to still "get it up", but they're shooting blanks by the third or fourth day). A quick look at the scrotum tells the story: chimp testicles are golf ball size or larger, with five times the volume of human ones.
Yet in the end, the author reports that there is a similarity, even a sameness, that he could feel. Near the end of years of travel and interviews, he had the opportunity to "visit" a group of wild chimps in a research area in Africa. After a few hours of watching them quietly feeding, he simply felt he knew what was going on, the way you or I might feel at a family gathering, where nobody may be saying much, but there is a comfort and kinship there, and you know what is going on. Chimps are social, and people are even more social, and that sociability overlaps in a way that we cannot experience with any other species.
We and chimpanzees, chimps and us: we are too different to be the same, but we're too similar to be wholly alien.
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