…when experienced field workers who follow apes around in the tropical forest tell me about the concern chimpanzees show for an injured companion, bringing her food or slowing down their walking pace, or report how adult male orangutans in the treetops vocally announce which way they expect to travel the next morning, I am not averse to speculations about empathy or planning. Given everything we know from controlled experiments in captivity, such as the ones I conduct myself, these speculations are not far-fetched.

To understand the resistance to cognitive explanations, I need to mention a third ancient Greek: Aristotle. The great philosopher put all living creatures on a vertical Scala Naturae, which runs from humans (closest to the gods) down toward other mammals, with birds, fish, insects and mollusks near the bottom. Comparisons up and down this vast ladder have been a popular scientific pastime, but all we have learned from them is how to measure other species by our standards. Keeping Aristotle’s scale intact, with humans on top, has been the unfailing goal.
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Humans: Not So Special

Here is a simplified version of the antiquated Scala Naturae, a ranking by presumed superiority that has been accepted in various forms for centuries. But advanced skills once associated only with humans are found in many animals, defying such rankings. Here is a selection. But think about it: How likely is it that the immense richness of nature fits on a single dimension? Isn’t it more likely that each animal has its own cognition, adapted to its own senses and natural history? It makes no sense to compare our cognition with one that is distributed over eight independently moving arms, each with its own neural supply, or one that enables a flying organism to catch mobile prey by picking up the echoes of its own shrieks. Clark’s nutcrackers (members of the crow family) recall the location of thousands of seeds that they have hidden half a year before, while I can’t even remember where I parked my car a few hours ago. Anyone who knows animals can come up with a few more cognitive comparisons that are not in our favor. Instead of a ladder, we are facing an enormous plurality of cognitions with many peaks of specialization. Somewhat paradoxically, these peaks have been called “magic wells” because the more scientists learn about them, the deeper the mystery gets.

We now know, for example, that some crows excel at tool use. In an aviary at Oxford University in 2002, a New Caledonian crow named Betty tried to pull a little bucket with a piece of meat out of a transparent vertical pipe. All she had to work with was a straight metal wire, which didn’t do the trick. Undeterred, Betty used her beak to bend the straight wire into a hook to pull up the bucket. Since no one had taught Betty to do so, it was seen as an example of insight. Apart from dispelling the “birdbrain” notion with which birds are saddled, Betty achieved instant fame by offering proof of tool making outside the primate order. Since this capacity has by now been confirmed by other studies, including one on a cockatoo, we can safely do away with the 1949 book “Man the Tool-Maker” by the British anthropologist Kenneth Oakley, which declared tool fabrication humanity’s defining characteristic. Corvids are a technologically advanced branch on the tree of life with skills that often match those of primates like us.

Convergent evolution (when similar traits, like the wings of birds, bats and insects, appear independently in separate evolutionary branches) allows cognitive capacities to pop up at the most unexpected places, such as face recognition in paper wasps or deceptive tactics in cephalopods. When the males of some cuttlefish species are interrupted by a rival during courtship, they may trick the latter into thinking there is nothing to worry about. On the side of his body that faces his rival, the male adopts the coloring of a female, so that the other believes he is looking at two females. But the courting male keeps his original coloring on the female’s side of his body in order to keep her attention. This two-faced tactic, known as dual-gender signaling, suggests tactical skills of an order no one had ever suspected in a species so low on the natural scale. But of course, talk of “high” and “low” is anathema to biologists, who see every single organism as exquisitely adapted to its own environment.

Now let us return to the accusation of anthropomorphism that we hear every time a new discovery comes along. This accusation works only because of the premise of human exceptionalism. Rooted in religion but also permeating large areas of science, this premise is out of line with modern evolutionary biology and neuroscience. Our brains share the same basic structure with other mammals — no different parts, the same old neurotransmitters.

Brains are in fact so similar across the board that we study fear in the rat’s amygdala to treat human phobias. This doesn’t mean that the planning by an orangutan is of the same order as me announcing an exam in class and my students preparing for it, but deep down there is continuity between both processes. This applies even more to emotional traits.

This is why science nowadays often starts from the opposite end, assuming continuity between humans and animals, while shifting the burden of proof to those who insist on differences. Anyone who asks me to believe that a tickled ape, who almost chokes on his hoarse giggles, is in a different state of mind than a tickled human child has his work cut out for him.

In order to drive this point home, I invented the term “anthropodenial,” which refers to the a priori rejection of humanlike traits in other animals or animallike traits in us. Anthropomorphism and anthropodenial are inversely related: The closer another species is to us, the more anthropomorphism assists our understanding of this species and the greater will be the danger of anthropodenial. Conversely, the more distant a species is from us, the greater the risk that anthropomorphism proposes questionable similarities that have come about independently. Saying that ants have “queens,” “soldiers” and “slaves” is mere anthropomorphic shorthand without much of a connection to the way human societies create these roles.

THE key point is that anthropomorphism is not nearly as bad as people think. With species like the apes — aptly known as “anthropoids” (humanlike) — anthropomorphism is in fact a logical choice. After a lifetime of working with chimpanzees, bonobos and other primates, I feel that denial of the similarities is a greater problem than accepting them. Relabeling a chimpanzee kiss “mouth-to-mouth contact” obfuscates the meaning of a behavior that apes show under the same circumstances as humans, such as when they greet one another or reconcile after a fight. It would be like assigning Earth’s gravity a different name than the moon’s, just because we think Earth is special.

Unjustified linguistic barriers fragment the unity with which nature presents us. Apes and humans did not have enough time to independently evolve almost identical behavior under similar circumstances. Think about this the next time you read about ape planning, dog empathy or elephant self-awareness. Instead of denying these phenomena or ridiculing them, we would do better to ask “why not?”
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There is nothing wrong with the recognition that we are apes — smart ones perhaps, but apes nonetheless. As an ape lover, I can’t see this comparison as insulting. We are endowed with the mental powers and imagination to get under the skin of other species. The more we succeed, the more we will realize that we are not the only intelligent life on earth.

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Frans de Waal, a primatologist and professor of psychology at Emory University, is the author, most recently, of “Are We Smart Enough to Know How Smart Animals Are?” from which this essay is adapted.