February 2007

Barbara J. King


Human Evolutionís Six Degrees of Separation: Chip Walterís Thumbs, Toes, and Tears

Science journalists spice my life. Tuesdays are notable in my house not only because Gilmore Girls airs (my daughter and I are loyal hangers-on, even though deep down we know the glory days are over) but also because the Science Times publishes. The deep vein of knowledge exposed and the surprising phrase of analysis offered by Science Times writers invite me to explore topics about which I know next to nothing, say octopus intelligence or the universe’s dark matter. But they illuminate for me subjects I’m paid to know a fair amount about, also, such as monkey communication or the evolution of culture. 

And that’s the mark of the best science journalists, I think -- they alter the thought landscape of novices and experts alike, offering arguable interpretations while conveying the basics with practiced accuracy. Writers in this category are found well outside the all-the-science-news-that’s-fit-to-print venue, of course. In BlogWorld, Carl Zimmer and John Hawks shine on all things human-evolutionary. 

Lacking the Michiko Kakutani gene, I feel no glee in concluding that, when we apply this metric, science journalist Chip Walter’s Thumbs, Toes, and Tears fails to satisfy. The book is saturated with surprising and serious errors.

The six anatomical and emotional changes chosen by Walter as the ones that made us uniquely human are debatable, but enjoyably so: paleoanthropology is a theorizing game, and it’s a fun game to play. I don’t refer to this aspect of the book. Rather, I identify three categories of transgression: internal inconsistencies that invite confusion; mangled facts; and a peculiar interpretation of evolutionary progress. Although Walter’s credentials (ex-CNN bureau chief, contributor to Scientific American) look great, and he writes with confidence (snagging for himself some notable back-of-the-book praise), he leads readers right into trouble.   

What are the six factors that, according to Walter, make us unlike any other species in the animal kingdom? (Anyone surly enough to point out that the poison dart frog and the woolly spider monkey too are unlike any other species in the animal kingdom just isn’t thinkin’ like a proud Homo sapiens). Here’s the list: big toe, opposable thumb, oddly shaped pharynx, and our abilities to laugh, cry, and kiss.

This list is enough to send a primatologist into "but but but!" mode, and yes, I do think Walter underestimates the abilities of nonhuman primates, especially the great apes. But given that human uniqueness is his focus, he’s right to go after the major patterns of difference, and when he’s writing about The Big Six he can be very good.  On the human hand: “Never before have five digits, fourteen joints, and twenty-seven bones come together in such an interesting and practical way. If you turn it, eight cubelike bones connected by a matrix of tendons in your wrist and forearm enable you to rotate your hand 180 degrees. This makes it possible to do things that animals in the natural world, even if they had the inclination, could never possibly carry off, like swing a baseball bat, pour a glass of milk, play a Duke Ellington piano solo, or paint a portrait.” I’d point out that we humans are part of the natural world, and I know an ape or two who could pour a mean glass of milk, but still, Walter nails this passage.

On crying, who knew that tears shed for emotional reasons differ appreciably in chemical make-up from tears that flow because we’ve been poked in the eye? The implications of this distinction, I found quite interesting.

Too, Walter is refreshingly unwilling to split apart intelligence and emotion, as too many human-origins theories still do: “The traditional view of human evolution has been that as we grew more intelligent, we increasingly left our primal drives in the ancestral dust, shaking off the shackles of emotion and rising to a better self. In fact, that notion is backward. Our increased intellect hasn’t placed more distance between us and our old drives, it has amplified, reshaped, and enhanced them. Our emotional life is more complicated and enriched because of our intelligence, not because our intelligence has obliterated our less intellectual side. In fact, our big brains have created the immense emotional life we all enjoy. Primal drives that in a simpler being once largely focused on fight or flight, fear, hunger, satisfaction, and procreation have been transformed in us into complex emotions: love, hate, affection, friendship, jealousy, and every other possible combination of sin and virtue.”

Thus, laughing, crying and kissing all served to enhance emotional expression and person-to-person connection. Intriguing stuff. All the more a sin, then, to have to read the book with one’s error-detector turned up to full strength: 

First, internal inconsistencies -- On page 1, Walter writes about Africa at 6 million years ago. Then, “It would be another million years before the creatures that would eventually spawn the human race split off from those that later led to chimpanzees and gorillas.” On page 6, however, Walter talks about the first hominid at more than 6 million years ago, and three pages later, that very same hominid is described to be as many as 7 million years old. Not ten pages in, and paleoanthropology must seem a train wreck to readers! Debate ensues about these fossils, sure, but judge the most reasonable date and stick with it. Similarly, decide if upright walking began “a million years after our line split off from the common ancestor we shared with chimpanzees” or “we managed to go from knuckle-walking jungle apes to upright-walking savanna apes in a few hundred thousand years or less,” a pair of views expressed four pages apart. Decide if Neanderthals are folded into the Homo sapiens species -- or not. Decide if the robust australopithecines are in the genus Paranthropus -- or not.

Second, mangled facts: If Walter truly has knowledge of archaeological discoveries of “the first tools” of “axes, spears, and small knives more than two million years ago” -- axes and spears?!! -- he should call the Science Times immediately. (His timeline is off, by a lot.) Writing about the last common ancestors of apes and humans, Walter notes, “The evidence suggests that like today’s gorillas and chimps, they very likely fashioned no tools and communicated with a limited repertoire of calls, hoots, and grunts.” An asterisked note “clarifies” this as, “Chimps and gorillas sometimes use grass and sticks and rocks as tools, but they do not create tools from scratch.” Where to start? On the tool use, chimpanzees extensively modify objects into tools: if that’s not “fashioning” tools, I don’t know what is. Gorilla tool use is different and cannot be uncritically lumped with their excitable cousins’. And worst thing for someone like me who studies ape gesture: all the amazing nuance and sophistication of ape communication is leached out of Walter’s summary. Hooting and grunting apes? Oh please, been there and read that, via Steven Pinker. 

Judging of the Award for Most Unforgivable Gaffe ended in a tie. Candidate A: The paragraph that starts out talking about gorillas and chimpanzees, but refers in the next sentence to “monkeys.” Candidate B: Describing Alan Walker and Richard Leakey’s astounding fossil find in Kenya in 1984, Walter writes, “They realized they had discovered a new kind of creature. They called him Turkana Boy and named the species that he represented Homo erectus (the erect human).” Rewriting history isn’t recommended in a science book; Homo erectus was discovered in 1891 in Java.      

Third, peculiar interpretations: Walter implies that our ancestors were partway down the evolutionary road to glorious -- and inevitable -- humanness. If quizzed, I am sure he’d deny intending this. But how else to read a statement that the famous australopithecine Lucy’s pelvis wasn’t completely human “but it was getting there”? To say, “Homo habilis was edging increasingly toward humanlike behavior, intelligence, behavior, and relationships” is to adopt a lazy way of thinking that I try to coax my students away from; it jettisons an appreciation for hominids adapted to their own local environment at their own time in prehistory.

(And by the way, yes, I read the endnotes. None of my worries is lessened by knowing that the occasional fine-print amplification of a complicated point exists at the back of the book.)

I have noted already that Walter’s writing is sometimes clean, crisp, and compelling. But far too often it is not. Anyone who writes will create a clunker of a sentence now and again. I do. But good editors, and copyeditors, save us from ourselves. What happened here? Let’s peek at p. 29: “But once savanna apes stood up, estrus skin wouldn’t have been nearly as noticeable, hidden as it became between the two legs of an upright body,” and, “If estrus skin was hidden, and if buttocks were just beginning to evolve, scientists speculate that two changes may have occurred.” Turn the page and you’ll find, “Full, round female breasts might have evolved as a recapitulation of their newly developed bottoms.”

Thumbs, Toes, and Tears offers some cool ideas, including those in an epilogue on humans’ evolutionary future (Cyber sapiens!). But proceed with caution: don’t let a student of human evolution near it without intensive supervision.        

-- Barbara J. King would like to thank the Bookslut Reading Series audience: You’re the best! Thanks for coming out in cold January to hear about my new book, Evolving God.