It is a long-standing bias to consider human beings the sole intelligent creatures on earth. If intelligence is defined on the basis of our behavioral traits, including the capacities to speak or to think with the help of abstract concepts, then a self-fulfilling prophecy of human exceptionalism is unavoidable. Starting from ourselves (but who is “ourselves”? isn’t the human always culturally and gender-specific?), using ourselves as the yardstick for everything that matters, we only find what we have hidden at the outset of this treasure hunt, its outcome predetermined before it has had a chance to begin. Homo sapiens appears to be the exclusive seat of sapiencia (Latin for wisdom) factored into the very name of our species.
For scientists, however, the superiority of human intelligence over other primates is a mere hypothesis to be tested and subsequently verified or declined. That is what Esther Herrmann, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, and her associates set out to do by evaluating and comparing the “general reasoning” and “social-cognitive skills” of humans, chimpanzees and orangutans. Their conclusions, published in the journal Science, might come as a shock. Chimps and young children showed remarkably similar results on certain measures of the IQ (Intelligence Quotient) tests including spatial and quantitative abilities. Yet, both orangutans and chimps underperformed, in comparison to humans, on skills related to “dealing with the social world.”
Much depends, of course, on how we construe social skill and what we count as such: learning from others, cooperation in problem solving, or other phenomena. What is crucial, in my view, is that humans are not superior to certain non-human animals even within the confines of a truly anthropocentric concept of general reasoning. Cultural and scientific grounds are therefore quite ready for a cross-species conception of intelligence and its corresponding measurement in redesigned IQ tests.
Whether acknowledged or not, the real bone of contention is the meaning of intelligence, and that is where philosophers can join the conversation that has already drawn evolutionary biologists, anthropologists, and cognitive scientists. If we attempt to adopt the standpoint of the universal, well in excess of the limited context and realities of Homo sapiens, we will quickly realize that what we call intelligence is a feature of life itself, or, more precisely, of the multifaceted exchanges between an organism and its environment.
So vital are these interactions that authors of the likes of Aldo Leopold and Gregory Bateson insist on making the relational whole organism-environment the basic unit of intelligence. Now, a drastic revamping of the concept along the lines Leopold and Bateson suggest would prompt us to admit under its heading not only non-human primates but also other animals, plants, fungi, and unicellular organisms.
In my book Plant-Thinking: A Philosophy of Vegetal Life, I pointed out some formal similarities among the mechanisms plants, animals, and humans use in their interaction with the environment. As I wrote in that text: “The sensitivity of the roots seeking moisture in the dark of the soil, the antennae of a snail probing the way ahead, and human ideas or representation we project, casting them in front of ourselves, are not as dissimilar to one another as we tend to think.” Within the scheme of survival, each of these “devices” functions as a means to the ends of procuring the resources necessary for life from the outside world and avoiding (or protecting an organism from) the dangers that lurk there.
Perhaps we could argue that the exceptional character of human intelligence lies in the possibility of asking why? and what for? rather than how? But the questions and thinking of ends, glorified in ancient Greek philosophy, are particularly out of fashion today, in an age enamored with the values of efficiency and productivity. If it takes place at all, the contemplation of reasons for something—why it is the way it is—happens not when things work smoothly but, on the contrary, when a malfunction creeps into the means we are accustomed to using in order to achieve our goals. The supposed marker of human exceptionalism is thus a sure symptom of non-adaptation, the incongruity between us and our milieu, a lack of fit between the environment and ourselves.
The paradox of our intelligence is sharply outlined here. One of the most successful species on the planet, spread over the entire surface of the earth, Homo sapiens threatens to destroy its own and other species’ life-support systems. Our evolutionary success is a spectacular failure; our marvelous capacity for adaptation that molds virtually any environment to our needs is, simultaneously, a catastrophic non-adaptation to the finite and fragile ecosystems we strive to dominate and control. How to measure this strange intelligence that is indistinguishable from stupidity? With the help of what IQ tests?
Seeking examples of intelligence in extra-terrestrial worlds or in humanly devised artificial systems is another marker of smart stupidity, which overlooks the wisdom embodied in non-human forms of life. To reverse millennia of such disregard in the West, nothing would do short of devising a cross-species and cross-kingdoms measure of intelligence—call it a general biological Intelligence Quotient (gb-IQ)—that would assess how successfully participants as diverse as an oak, a mouse, and a human adapt to their respective environments, collaborate with others, solve problems, and so forth.
Needless to say, we would not be able to administer a questionnaire to an oak or to a mouse, but neither is that possible with a three-year-old child. Our interpretative faculties would have to work hard to carry out a gb-IQ exercise. Furthermore, problem solving, collaboration, and adaptation would need to be indexed to the appropriate environments and needs of each kind of organism, be it an underground labyrinth of mineral resources and moisture in the case of a tree or a complex network of social interactions holding the promise of positive reinforcement in the case of a human child. Although many of the circumstances are going to be wildly dissimilar, a common ground will gradually emerge (admittedly, thanks to our power of generalization and abstraction) for a less species-biased conception of intelligence.
Assuming that a gb-IQ test could be administered, with the myriad of imperfections that are bound to plague this project, researchers are likely to discover areas of overlap between, as well as variations within, each participating species. Neither all oaks will be equally smart, nor all mice uniformly intelligent, nor all humans the same when it comes to their IQ. Conceivably, there will even be some oaks smarter than some mice, or certain mice smarter than certain humans. Acceptance of this outcome would be a sign of humility and of intelligence on our part.
Michael Marder is IKERBASQUE Research Professor of Philosophy at the University of the Basque Country (UPV-EHU), Vitoria-Gasteiz, Spain. His most recent monographs include The Philosopher’s Plant: An Intellectual Herbarium (2014), Pyropolitics: When the World Is Ablaze (2015), and Dust (2016). He is now completing a book, co-authored with Luce Irigaray and titled Through Vegetal Being.
 Esther Herrmann, et al. “Humans Have Evolved Specialized Skills of Social Cognition: The Cultural Intelligence Hypothesis”, Science, vol. 317, no. 5843, pp. 1360-1366. DOI: 10.1126/science.1146282.
 Michael Marder, Plant-Thinking: A Philosophy of Vegetal Life (New York: Columbia University Press, 2013), p. 27.