Nov. 15, 2013 3:23 p.m. ET
Why is our species different from all other species? This isn’t a Passover Seder question but a genuine scientific one that can be divided into two parts: How are human beings different from others, and by what means has this difference come about? It turns out that neither question has a simple answer, although the former may be more amenable to productive inquiry.
For “true believers” among the Big Three Abrahamic religions—Judaism, Christianity and Islam—there is no problem answering either question. Why are we different? Easy: because we Homo sapiens possess immortal and God-given souls, chips off the old Divine Block. And what produced this difference? Also easy: Hashem, or God, or Allah made us that way. Things aren’t so simple, however, for a scientist, even though Thomas Suddendorf is a good one—a remarkably good writer, too, as he leads the reader on a rewarding, thought-provoking journey to understand what he calls ” The Gap “: not the clothing and accessories retailer but the hard-to-define qualities that distinguish our species from the rest of the organic world.
By Thomas Suddendorf
Basic, 358 pages, $29.99
Rock paintings from the Neolithic era in the Tassili n’Ajjer mountains in what is now Algeria. Thousands of images made beginning as early as 8,000 B.C. depict cattle, crocodiles and humans. Gamma-Rapho via Getty Images
I was favorably disposed toward Mr. Suddendorf’s book as soon as I saw its subtitle: “The Science of What Separates Us From Other Animals.” Not only is “science”—rather than theology—right up front, but instead of embracing the frequently employed but altogether misleading construction that sets people apart from animals, the phrase makes clear that human beings are to be treated as just another species. Mr. Suddendorf, I am pleased to note, has no doubt that, whatever else we are, we are also animals, although this doesn’t blind him to a degree of self-proclaimed (and likely justified) species-centrism.
“The physical continuity of humans and animals is incontestable,” he writes. “But the mind is another matter.” We think, therefore we are . . . special. (Ambrose Bierce modified Descartes’s famous “cogito” as follows: “I think that I think, therefore I think that I am,” adding that this was as close to certainty that philosophy was likely to get. Thanks to researchers such as Mr. Suddendorf, comparative psychology, informed by evolutionary biology, may well get closer yet.) But then again, when it comes to its presumed specialness, every species is unique; that’s how we identify any species as distinct. “Always remember that you are absolutely unique,” wrote anthropologist Margaret Mead, “just like everyone else.” Although she was referring to individuals, she could have had all human beings in mind.
There is quite a history of scientists as well as philosophers trying to distill the unique essence of humanness, attempting to improve upon Linnaeus’s Homo sapiens (“Man the knowing,” or “wise”). Such attempts have included H. ludens (“the player”), H. religiosus (“the religious”), H. lingua (“the language-user”), and H. cultura (“the culture-using”), as well as some tediously anatomical monikers, such as H. glaber (“hairless”) and H. bipedalis (which should be self-explanatory). Over time, most of these traits have been shown to be “less unique” than their promoters had hoped.
If we limit ourselves to animal language alone, cases of remarkable capacities—verging on the human—are legion. For example, vervet monkeys have four acoustically distinct kinds of predator-alarm calls, evoked by leopards, eagles, pythons and baboons. And even non-primates come close to human language. Prairie dogs—not normally considered among the brightest bulbs in the animal chandelier—have different alarm calls for humans, coyotes, domestic dogs and red-tailed hawks. Moreover, they employ modifiers that even specify the size and shape of an individual predator.
Research by Irene Pepperberg on her pet African gray parrot strongly suggests that he could understand and employ nouns, verbs and adjectives, as well as sophisticated concepts such as “different.” And the brilliant border collie Rico not only learned more than 200 distinct words but, when asked to identify an object that he didn’t know amid several other items, all of which he had previously identified, he correctly chose the new and unknown object—a mental feat that is not only remarkable but also replicable and that cannot be explained except by granting this animal extraordinarily complex mental agility.
Some decades ago, one of the more promising candidates for human uniqueness was Homo faber: man the tool-user. But in the early 1960s, a young Jane Goodall—studying free-living chimpanzees in Tanzania’s Gombe National Park—watched two of her subjects pick up twigs, strip off the leaves and smaller branches, and use them to “fish” for termites. Not only were these animals using tools, they were making them! When Ms. Goodall’s mentor, Louis Leakey, received her excited account, he famously wrote back: “Now we must redefine ‘tool,’ redefine ‘man,’ or accept chimpanzees as humans.”
None of these possibilities transpired, and the search for human uniqueness went on. Chimps have been found to chew leaves and then dip them into otherwise inaccessible puddles of water, using the mashed mess as a sponge to soak up moisture; at a different location, they were observed smashing recalcitrant nuts with stones. Other animals, including several bird species, are also known to employ tools. “He who understands baboon,” jotted Charles Darwin in one of his notebooks in 1838, “would do more towards metaphysics than Locke.” Thanks to a veritable army of field researchers, we understand baboons quite well these days—albeit not entirely—and yet the metaphysical payoff remains elusive.
Into this gap comes “The Gap,” offering an easily digested and suitably unbiased overview of the current state of what comparative psychologists have discovered about the traits typically considered to be uniquely human: language, intelligence, morality, culture, “theory of mind” and “mental time travel.” When it comes to interpreting examples of seemingly insightful animal behavior, Mr. Suddendorf employs philosopher Daniel Dennett’s dichotomy of “romantics” vs. “killjoys”: Romantics posit mental processes in animals that are similar to our own, and killjoys look for simpler, more “instinct-based” interpretations. In describing their debates, Mr. Suddendorf cuts an entertaining swath through a thicket of research studies on primate cognition, of which most of the original technical accounts I at least have always found terribly boring.
The author’s style is not only consistently interesting and informative but at times delightfully playful, as when he describes how human language—unlike the communication systems of other animals—is governed by rules of word order or syntax. “You may remember some of them from school (or you may remember that you have forgotten them),” he writes. “Even if you are not able to explain them, you still know when they violated being are.”
Mr. Suddendorf’s goal is to answer this seemingly simple question: “Which characteristics of the human mind, be they distinct traits or gradual differences, enable and motivate us to do the great diversity of things that other animals do not? What makes us human?” He points to two “master adaptations” as fundamentally responsible for The Gap: a purported “drive to connect with other minds” and what he calls “nested scenario building”—aka mental time travel. We struggle not only to be understood but often to maximize the number of others with whom we are able to communicate (think of blogging and Twitter). We are also predisposed to imagine situations without necessarily experiencing them and to imagine what someone else is imagining: “I think she thinks that I think that she likes me.” But here Mr. Suddendorf is regrettably, and surprisingly, unpersuasive, since the evolutionary relevance of these characteristics is simply asserted, and then reasserted, rather than demonstrated.
One can point to any number of other defining human traits, as did Mark Twain when he proclaimed that “man is the only animal that blushes—or has reason to.” We may also be the only animal that wastes energy and efforts engaging in spite, thereby demonstrating a unique degree of independence from those fitness-maximizing tactics to which other animals are bound by the dictates of natural selection. Primatologist Richard Wrangham has made an impressive case that—strange and simplified as it may seem—cooking was our ancestors’ key humanizing adaptation. And language still remains a strong candidate, as does death awareness, as championed by the late anthropologist Ernest Becker.
Mr. Suddendorf does a good job of discussing the fraught question whether other apes possess a theory of mind, which involves developing a mental picture of what another individual knows or is thinking. The adaptive significance of such a theory is presumably that it allows humans to navigate the complex, shifting shoals of social existence. We might call it the Burns Benefit, after the poet’s plaint: “O wad some Pow’r the giftie gie us, / To see oursels as ithers see us! / It wad frae mony a blunder free us, / An’ foolish notion.”
I was disappointed to find no serious consideration of the role of consciousness in generating the Gap. My German Shepherds are exquisitely alert, responsive to and aware of their environment, much more so than I. But insofar as they lack a recursive awareness of their own awareness, I think we are justified in questioning whether they are conscious, at least as human beings are. My own guess—and it is little more than a guess—is that consciousness underlies many of the uniquely human traits that contribute to the Gap.
There is, nonetheless, much to admire in “The Gap”—the book no less than the phenomenon. Despite its imperfections, it is a welcome addition to the growing literature explaining science to the intelligent layperson, although a clarification is in order: Publicity surrounding this book gives the impression that it develops the thesis that human beings are taxonomically as well as metaphysically alone because we have likely killed off our near-relatives. This is an attention-grabbing notion, one that may indeed be true and could well warrant its own book-length treatment; certainly, as Mr. Suddendorf, to his credit, points out with appropriate outrage, we are currently pushing our existing great-ape relatives to the brink of extinction.
But at present we simply don’t know if other species in the direct line of descent to Homo sapiens (known these days as “hominins”) disappeared because they were ill-adapted to changing environments or if our ancestors killed them off directly, “defeated” them indirectly via ecological competition, swamped their genomes by interbreeding. Or it could be that our current existential and biological loneliness is due to something else. It is even possible, as suggested by the fossil of H. erectus recently found in the European state of Georgia, that there weren’t that many different hominin species similar to us after all. In any event, you have just now read more about what might have befallen our ancestral and collateral relatives than you will find in all of Mr. Suddendorf’s book.
Mr. Suddendorf’s lively attempt to discover what exactly makes humans different from other species raises other questions. What is the adaptive significance, the evolutionary payoff, of these Gap-generating traits, whatever they may be? Why should natural selection have favored early human ancestors who were able to engage in mental time travel, or who strove to link their minds with others, or who achieved consciousness? Was there a payoff in terms of intergroup competition, within-tribe coordination, enhanced sexual opportunities or something not yet identified?
However you slice it, there is much to be said for the ancient Greek aphorism “Know Thyself,” and “The Gap” is an excellent place to start.
—Mr. Barash is an evolutionary biologist and professor of psychology at the University of Washington. His most recent book is “Buddhist Biology.”