On Human Non-Exceptionalism

Moving the goal posts isn't only a football metaphor.

Posted Apr 15, 2018

Like it or not—and lots of people don't—a scientific take on Homo sapiens reveals us to be less special and more “natural” than an anthropocentric perspective on the human condition would like. In his essay, Anti-Semite and Jew, Jean-Paul Sartre wrote that the underlying basis of existential freedom can be found in what he calls “authenticity,” the courage and capacity to have “a true and lucid consciousness of the situation, in assuming the responsibilities and risks it involves, in accepting it in pride or humiliation, sometimes in horror and hate.”

Lest there be any misunderstanding, I am not a species-hating human being, although I maintain that we—along with the rest of the planet and its inhabitants—would all be better off if our species-wide narcissism was taken down a peg or two. Science is supposed to be divorced from pride, humiliation, horror and hate, and to a large extent, it is. However, as biological anthropologist Matt Cartmill pointed out in a brilliant essay more than 25 years ago, when it comes to scientific investigations into human-ness, there has been a persistent tendency to move the goal posts whenever other species turn out to have traits that had previously been reserved for Homo sapiens alone. As soon as our biological uniqueness is challenged, there has been a scramble to redefine the characteristic in question so as to retain precisely that specialness.

Take brain size. Intelligence is obviously one of our most notable characteristics, which led to the assumption that the human brain must be uniquely, extraordinarily, exceptionally, and altogether wonderfully large. But as Cartmill points out, the weight of the Homo sapiens brain (1-2 kgs) bumped up against the awkward fact that the brains of elephants (5-6 kgs) and whales (up to 7 kgs) are larger yet. This unwanted and uncomfortable reality brought forth a focus on relative brain size—comparing species by looking at brain weight in proportion to body weight. Gratifyingly, it happens that this number is substantially higher for Homo sapiens (1.6-3.0%) than for elephants (0.09%) or whales (0.01-1.16%). So far, so good.

public domain wikipedia
Source: public domain wikipedia
public domain wikipedia
Source: public domain wikipedia

         However, Cartmill notes that even in the realm of relative brain size, we are equaled or exceeded by that of many small mammals, including squirrel monkeys (2.8-4.0%), red squirrels (2.0-2.5%), chipmunks (3.0-3.7%), and jumping mice (3.4-3.6%). And so, “algometric analysis” was then “invoked to rescue the axiom of human cerebral preeminence. The first step in such an analysis is to assume that the interspecific regression of the logarithm of brain weight on that of body weight ought to be a straight line.” Without getting into the details of algometric analysis, suffice it that even with this mathematical adjustment, porpoises ended up being “embarrassingly” close to human beings and so another way out was needed.

public domain wikipedia
Source: public domain wikipedia

What about assuming that brain size should be proportional to an organism’s total metabolic energy expenditure, i.e., looking at the amount of energy invested in each creature’s brain in proportion to its total energy budget? Sure enough, if we obtain a measure of total metabolic expenditure, by multiplying body weight times baseline metabolic rate, it turns out that porpoises invest proportionately less energy in brain maintenance than do human beings. Even in this case, however, there is a problem, since as Cartmill observes, it is “a maneuver that a lizard might with equal justice use to prove that mammals don't really have bigger brains than reptiles, but only higher metabolic rates.”

public domain wikipedia
Source: public domain wikipedia

The above brain brouhaha doesn’t even touch the case of learning capacities among insects, whose brains are small indeed: fruit flies average only about 250,000 neurons per brain, and yet they are capable of learning to avoid certain stimuli and to seek out others, to orient themselves via a mental map of their surroundings, and so forth. Moreover, bumblebees—which have approximately one million neurons in their brains (a gratifyingly small number compared to mammals)—have recently been shown capable of learning to do something unlike any behavior they are likely to encounter in nature, namely to roll a little ball into the center of a platform in order to receive a small dose of sugar water. Not only that, but individual bumblebees learn this relatively complex and heretofore unfamiliar behavior more rapidly if given the opportunity to watch other bees learning the task. “Observational learning” of this sort had previously been considered a sign of higher mental powers, especially found in, well, us.

public domain wikipedia
Source: public domain wikipedia

Writing about shared “intellectual faculties,” Darwin conceded in 1871 that “Undoubtedly, It would have been very interesting to have traced the development of each separate faculty from the state in which it exists in the lower animals to that in which it exists in man; but neither my ability nor knowledge permit the attempt.” A lot has happened in the intervening century and a quarter, and although the evidence is accumulating rapidly, it is also resisted by many—and not just religious fundamentalists and spokespeople for the beef and dairy industries.

The struggle against recognizing mental continuity between humans and other animals has taken place in many domains, including, for example, language, the meaning of which has regularly been revised whenever detailed research revealed that nonhuman animals possessed it. Once it became evident that other creatures communicated sophisticated information to each other (such as the “dance of the bees,” whereby a forager communicates complex information about the location and even the desirability of a food source to her hive-mates) language was redefined as synonymous with something else: the establishment of arbitrary signs, such as the word “dance” meaning a pattern of complex, rhythmic movements, as opposed to whatever is involved in doing any particular kind of dance.

The persistent search for human exceptionalism whereby our biology renders us discontinuous from other animals is, if not quite a fool’s errand, one persistently undertaken by a subset of Homo sapiens who—so long as they base their search on science rather than metaphysics or theology—are doomed to disappointment.

The best view in Warsaw, Poland, is from the top of the Palace of Science and Culture, because that is the only place in the city from which one cannot see this example of Stalinist architecture at its worst. Being too close to the object of our scrutiny is inevitably a problem, which makes it all the more difficult—as well as important—to take a close and careful look at ourselves, mindful that any such view (even, perhaps, the evolutionary one that I so enthusiastically espouse) is liable to distortion and, conceivably, to revision.

David P. Barash is professor emeritus of psychology at the University of Washington. His most recent book, Through a Glass Brightly: using science to see our species as we really are, will be published summer 2018 by Oxford University Press.