The Continuity Wars

by Frans B. M. de Waal

Something curious is underfoot in the science of human vs. ape comparisons.

For a long time, we’ve been used to scientists who believe we’re totally unique. They simply don’t see humans as part of the animal kingdom, are uninterested in evolution, and indeed uninterested in any meaningful cross-species comparison. They just react with horror to any hairy creature that looks like them, the way Queen Victoria declared the apes displayed, in 1835, at the London Zoo "frightful, and painfully and disagreeably human."

It is different now. We’re dealing with scientists who believe in evolution, claim an interest in it, and sometimes even have great expertise, yet balk at accepting mental continuity between humans and their closest relatives. Admittedly, most of them have a background in the social sciences, such as anthropology or psychology, not biology, which may explain why they argue that Charles Darwin was actually mistaken on this issue and that the cognitive gap between a human and an ape is in fact so wide that it may exceed that between an ape and a beetle.

A beetle? Have they ever seen a beetle brain next to a chimp’s?

Darwin could not have been clearer, saying in The Descent of Man: “… the difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind.” The evolutionary framework simply has no room for saltationist arguments. Like Darwin, I am not claiming that humans possess absolutely no unique mental capacities – I am sure they do - but these capacities are merely the tip of the iceberg, and I prefer to look at the whole “berg.”

Except for a few differences at the microscopic level, the human brain is barely distinguishable from the ape brain. Its structure, neurotransmitters, and functional connections are all the same. Even our much-heralded frontal cortex turns out to be about the same size as an ape’s relative to the rest of the brain. Since we don’t assume that the human heart or liver work any differently than those of other animals, why shouldn’t this apply to the stuff between our ears? Yes, the human brain is three times larger, but this only means that it can do more, or do certain things better.

We now seem to have two schools of primate researchers. The “gradualists,” who follow Darwin on both counts (evolution and continuity), and the “exceptionalists,” who follow only half the theory. They propose major mental and behavioral differences, often focusing on just one that they feel explains everything that makes our species unique. Even the major scientific journals are taking sides, with Nature publishing more gradualist papers and Science more exceptionalist ones. Entire research institutes are split, such as two directors at the Leipzig Max-Planck for Evolutionary Anthropology, with one director publicly criticizing another on this issue.

Claims and counter-claims arrive at a pace that must be hard to follow for the outside world. For example, a recent exceptionalist paper on how altruism is sadly absent in the apes, hence must be uniquely human, was soon followed by a gradualist correction about how altruism is alive and well in chimpanzees (see my commentary on both). Or a recent prominent paper about highly developed social learning in chimpanzees was forgotten, and in fact unmentioned, when Science published a report about the limits of chimpanzee social cognition. This prompted our recent commentary in Science - which the journal published four months later - about the best way to compare human and ape cognition.

Our main critique was that if both children and apes are tested by human experimenters, this is unfair to the apes. On the surface, the procedures look identical, but the apes are the only ones facing a species barrier. They obviously don’t relate as well to adult humans as children do. Another difference is that children often sit on or next to their parent during testing, meaning that the parent can give all sort of unintentional clues that assist performance, whereas the apes lack this advantage. In fact, apes have been tested for decades in ways that almost guarantee underperformance.

We do have solutions to this problem. A recent study on dog cognition was conducted in the pet owner’s presence, but with the owner blindfolded. This way, they excluded unwanted influences known as “Clever Hans” effects. Shouldn’t children, too, be tested in a way that cancels parental influence?

I do think there is room for careful human/ape comparisons, and that most of the time (but not always) these will come out in favor of the primate with the larger brain. Humans are different, but not as drastically as claimed. The bigger task that we face is not to assign the gold, silver, and bronze medals of smartness in the animal kingdom, but to see what kind of processes underlie all cognition, both human and animal. Evolutionarily speaking, the more parsimonious assumption is that related species will handle similar problems in similar ways, using the same brain areas, (mirror) neurons, and connectivity.

This is something to keep in mind when the next paper comes along postulating a huge human vs. ape difference. My bet is always on the similarities, and indeed over my lifetime I have seen tons of claimed differences fall by the wayside, but rarely a claimed similarity.

A nice illustration is the work on imitation by Vicky Horner and others. Even though everyone uses the word “aping” for imitation, it was until recently held that apes are actually not good at it. Apes were said to lack “true” imitation based on the fact that, most of the time, they refuse to follow the human example. When we removed the human experimenter from the picture, however, and looked at imitation from ape to ape, all of a sudden they turned out to be excellent, faithful copiers of behavior. So, apes actually do ape!

This won’t deter the exceptionalists, however. They have already begun to turn their attention to the next major difference.

The most amusing one I have ever seen occurred in a Dutch newspaper by a serious philosopher writing about man’s place in nature. He proposed that humans differ from all other animals in that only we go on vacation. A sea lion may lie on the beach, he wrote, but not with the purpose of relaxation. Only we set aside time for this.

Perhaps we should just grant him his little distinction, and not fight it, so that we can finally close this line of argument and move on to more important matters.

Trained as an ethologist and biologist, the Dutch-born Frans B. M. de Waal is C. H. Candler Professor in Psychology and Director of the Living Links Center at Emory University, in Atlanta, Georgia, USA.

Comments

[D]

- Thanks for the insightful article
- What about grammar, especially recursive grammar? To my knowledge, linguists have tended to be extremely skeptical of claims involving language and non-human animals.

[Felix E. F. Larocca MD]

When E. O. Wilson spoke of sociobiology he drew the fire from his own colleagues at Harvard who were (as the rest of the world was) opposed to a new and original view point on the held dogma.

Frans de Waal on his superb contribution, tells us of scientific hubris, not in kind different, from the one of the non-scientist.

Because, apes are apes --- and we?

We are just simians...

[JonJ]

de Waal is quite right about continuity here, but I suppose it comes down in the end to how impressed one is by the similarities and differences between Homo and our relatives.

For example, I found it interesting that, in his proposal to reduce the experimental differences between studying apes' behavior and children's, he suggested modifying the way the human half of the experiments are conducted, but of course didn't suggest that we arrange (or wait) for the apes to conduct experiments among each other.

Doesn't the fact that we do scientific experiments but apes aren't the least interested in science suggest an important difference? Well, some people might be impressed by this difference and others not. Perhaps we are not dealing with a strictly scientific issue here, but a more philosophical one, one could say, about evaluating the importance of similarities and differences.

[Marilyn Terrell]

More on animal cognition, including the superstars of the Vienna dog cognition study, in the March issue of National Geographic:
http://ngm.nationalgeographic.com/2008/03/animal-minds/virginia-morell-text

[Barkley]

As much as I like using science to knock us humans off of our pedestal, the level of cognition being (sometimes) convincingly established in animals is pennies compared to the immense riches of what the human brain can do. So although it is very important to flesh out the cognitive wonders some animals are capable of, talking as though they are practically human is losing all sense of scale and perspective.

Felix, while it is true that apes are apes and that we are simians, apes are also simians and we are also apes. Or perhaps I'm missing your point...

[Justin]

Frans,

What a pleasure to find a contribution from you at 3QuarksDaily. One of the most eye-opening and transformative books I read while in grad school was your Chimpanzee Politics, and while I ended up sticking it out for a career in academic philosophy, from that moment on I've had the sharp sense that philosophers continue, in more or less naturalized terms, to try to hold on to the mystified uniqueness of humans that used to be explicable in terms of the inherence of a soul. Richard Sorabji nicely charts the trajectory of our uniqueness claims as moving from the lack of a soul to the lack of language, and, when that could not be defended, to the lack of an infinitely generative syntax, and he asks what of any moral significance ought to hang on this distinction. "They lack syntax, so we can eat them" (or consider them as elaborate machines) does not seem a very compelling conclusion.

I've been doing some research on very early primatology, first on Pliny and Tulpius and more recently on Edward Tyson's anatomical study of an "Angolan Orang-Outang" (i.e., a chimpanzee) of 1699. In the end, having established the great similarity of human and chimpanzee neural anatomy, the only way for Tyson to hold on to the uniqueness thesis is to insist, along Cartesian lines, that the distinctive feature of humanity is not in any case an organic one, but is immaterial. The empirical evidence for our non-uniqueness has been beyond dispute since the 17th century. At that time, men of science could permissibly revert to a priori arguments that would preserve it, but these have rightly gone out of fashion.

Thanks again for your great contribution. I hope to see more from you here.

[Asad Raza]

Thanks for an informative and generally excellent summary article, Prof. de Waal--I hope you continue to write for the site.

Justin, I happened to read an article by Rorty last night ("On Wittgenstein, Heidegger, and Language") that makes a nice argument related to your comment: Rorty claims that the early Wittgenstein and the late Heidegger were committed to an immaterial or mystical uniqueness, and that this represents a (wrong-headed) attempt to conserve an environment for philosophy that cannot be encroached upon by science. Naturally, I agree with you that philosophical inquiries into these subjects should attempt to achieve continuity with scientific findings rather than distinguish themselves from it. (And as a side note, Rorty's implication is that Wittgenstein improved in his thinking on this over his life, while Heidegger regressed...)

[Frans de Waal]

Thanks for the support and additional information - I clearly need to read Sorabji. The debate is indeed old, and many crazy examples of human uniqueness have been proposed and subsequently been forgotten. It's like the quest for the holy grail. If the difference is immaterial, as Tyson proposed, this makes it harder to refute ... but also harder to substantiate.

Funny thing about Tulpius, who is Nikolaas Tulp (depicted in Rembrandt's "The Anatomy Lesson") is that he thought he had dissected an orangutan. The below part comes from my book "Bonobo" (1996):

"Although Tulp baptized his specimen an Indian satyr, adding that the local people call it an “orang-outang,” it had come straight from Africa. Only its name came from the East Indies. Tulp’s gravure, faithfully replicated over and over in books of the seventeenth and eighteenth centuries, appears to show a female chimpanzee. At least this was the consensus until a British primatologist, Vernon Reynolds, asserted that Tulp’s satyr could very well have been a bonobo. Reynolds’ chief argument was that the original drawing shows a cutaneous connection between the second and third digits of the ape’s right foot. Such “webbing” between toes is much more common in bonobos than chimpanzees. Furthermore, Tulp’s specimen was known to have originated from Angola. Although no bonobos live there today, Angola is located south of the Zaire River. This immense, at times more than one-kilometer-wide water barrier currently fully separates chimpanzees, to the north, east, and west, and bonobos, to the south."

[Justin Smith]

The Sorabji book I had in mind was Animal Minds and Human Morals: The Origins of the Western Debate (Cornell, 1993). He focuses mostly on the controversy over human uniqueness in late antiquity, but it's remarkable just how much, mutatis mutandis, has remained the same.

This short article of mine on the reasons for Tyson's refusal to acknowledge ape-human kinship may also be of interest: Justin Smith, "Language, Bipedalism and the Mind–Body Problem in Edward Tyson’s Orang-Outang (1699)," Intellectual History Review, 17, 3 (2007), 291.

Tyson seemed to be aware of the species difference between his African specimen and the East Indian orangutan, but persisted in using "Orang-Outang" (as well as "Pygmie" and "Homo sylvestris") as a generic term covering all known great apes. He disputes Tulp's use of the ancient label "satyr," and even devotes an entire "philological" chapter of his anatomical study to showing that mythological references to satyrs and other fantastic humanoids were probably just encounters with apes.

That's very interesting to think that Tulp's satyr may actually have been a bonobo. I didn't think to look for signs that Tyson's specimen may have been as well, but he does identify it, like Tulp's, as coming from Angola. I'll have to go back and check for the anatomical differences you mention.

[Leinad Kafka]

Prof deWaal must recall that he's blog is very excellent example that he is wrong. Chimps not have vacation--neither they write blogs.

If want to know truth: read Kafka.

I also thinks apes carry virus that affects human cognitive module. Decrease cognitive power. Maybe I catch too.