Book Club: Darwin’s Unfinished Symphony, 4, intelligence and high fidelity

Let us resume our discussion of Kevin Laland’s excellent Darwin’s Unfinished Symphony: How Culture Made the Human Mind, by tackling the first two chapters of the second part of the book: 6, on the evolution of intelligence, and 7, on high fidelity (of copying behaviors). Just to give you heads up, we are then left with five more chapters, likely each deserving its own post: why we alone have language, gene-culture coevolution, the dawn of civilization, foundations of cooperation, and the arts. The best has yet to come, and we will be at this for a while. But I assure you, it is worth it.

The chapter on the evolution of intelligence (#6) opens with a brief explanation of Allan Wilson’s observation, back in the ‘80s, of an interesting relationship between an animal’s brain size and the time since it had shared a common ancestor with humans: over the last 400 million years animal brains have grown 100-fold, and the growth rate has accelerated over time, a potential indication of a feedback mechanism at work.

Wilson proposed a three-step hypothesis, the so-called cultural drive scenario, to explain the evolution of intelligence:

1. A new advantageous habit arises in an individual through behavioral innovation.

2. The new habit spreads throughout the population by way of social learning.

3. Selection favors mutations that augment either the likelihood of innovation or the ability to engage in social learning.

Moreover, the expectation — which has been since empirical verified — was that new habits generate selection for changes in the animal’s anatomy that are better suited to the new behavior. Indeed, a good portion of this chapter is devoted to fleshing out Wilson’s original hypothesis, as well as to line up empirical evidence for it. (Laland was supposed to work with Wilson as a postdoc in 1991, but Wilson tragically died a month before Laland’s arrival.)

One of the issues in this discussion is that, quite obviously, large brains are not necessary for animals to take advantage of social learning — think of eusocial insects like bees and ants. The idea, however, is that larger brains evolved in primates because they make social learning increasingly efficient, and that trait is favored by natural selection.

Better learning — for instance through copying — in turn requires better perceptual systems, so that it is easier for an animal to copy another’s behavior (e.g., a fishing technique) at a safe distance. This, in turns, mandates an increasingly sophisticated type of integration across perceptual systems, as well as a precise mapping of sensorial inputs to behavioral outputs:

“To copy a fishing technique, for instance, the observer’s brain must convert a stream of visual information about how others move their hands and arms into corresponding outputs specifying how the observer must also move its muscles and joints. … Selection for copying proficiency might plausibly favor the evolutionary expansion of circuitry linking the visual and auditory cortex to somatosensory and motor cortex regions of the brain.” (p. 129)

Moreover, effective copying might also promote the evolution of what is often referred to as a “theory of mind,” meaning the ability of an animal to form an idea of the intentions, beliefs, and desires of other members of its own species. Not only that, but the cultural drive hypothesis also predicts that large brained animals should evolve pro-social traits (like tolerance for other members of the group, and cooperation), because learning requires allowing especially the young to hang around so that they can observe and copy advantageous behaviors.

Sure enough, for instance it is known that young chimpanzees hang around their mothers well after they are physically independent, until age seven or so. Presumably so that they can learn from observing, copying, and experimenting with her behaviors. Notice also that in most animals the innovators are adults with a lot of experience, another reason for the young ones to hang around as much as possible.

Larger brains, of course, are a necessary byproduct of the need for better and better cognition at so many levels. One of these levels has to do with the need to keep track of social interactions in increasingly larger groups, and an interesting observation is that the rate of “tactical deception” of other members of the group correlates positively with brain size in primates: the smarter we get, the more Machiavellian we become.

One of the studies conducted by Laland’s group that I found particularly interesting is a test, across species, of the standard evolutionary psychology hypothesis that minds are highly modular, i.e., that our brains work like cognitive Swiss Army knives, with each module evolved very specifically for a particular task or behavior. No such thing. A study of 62 primate species showed just one principal component explaining a very large amount of the variance in cognitive measures, with species excelling at one domain (say, innovation, social learning, tool use, etc.) also excelling at all others. Not that I sense any indication whatsoever that evolutionary psychologists have taken such results on board, of course. Moreover:

“Those species that were designated ‘smart’ by our statistical measure of primate intelligence turned out to be precisely those species that had performed well in laboratory-based experimental tests of learning and cognition.” (p. 138)

And just to make crystal clear what Laland thinks this means for evolutionary psychology:

“Such findings are inconsistent with the view, widespread within evolutionary psychology, that cognitive abilities evolve independently as separate modules, and the results strongly imply general intelligence [across primate species].” (p. 139)

The range of brain size (both in absolute and relative terms) in primates is huge, going from 3 g in fat-tailed dwarf lemurs to 1.5 Kg in humans. The overwhelming majority of the evolutionary increase is due to development of the neocortex, known in humans to be the locus for problem solving, learning, planning, reasoning, and language. And — no surprise here — our species possesses by far the largest (both in absolute and relative terms) and best connected neocortex of all primate species.

Why would such an increase in brain size, and particularly in the neocortex, be favored in primate lineages? Because productivity increases dramatically with age, once an animal has had sufficient time to learn a range of adaptive behaviors, so long as there is a reliable inter-generational flow of information, from older to younger individuals. Furthermore, mathematical models have shown that selection favors lower mortality rates and longevity when productivity increases over time the way it does in primates:

“By virtue of possessing a big brain, and being able to use it to acquire all kinds of useful survival skills from others, some clever primates had apparently been able to extend their lifespans and live longer. In other words, in primates and primates alone, cultural intelligence facilitates survival.” (p. 147)

Next, let us briefly discuss chapter 7, on “high fidelity.” It opens with a darn good question:

“If cultural drive has operated on all the great apes and some monkeys too, then why haven’t gorillas invented particle accelerators? Why haven’t capuchins put a monkey on the moon, or devised a simian version of Facebook?” (p. 150)

Even though I don’t think a simian version of Facebook would be an improvement on things, and even though some people may be inclined to dismiss the very question as framed by Laland, this does get to the core of the issue of cultural evolution addressed by the book. Why indeed?

Kevin considers a number of proposed answers. Maybe it was just chance. As he admits, chance explanations are hard to rule out, but they are also unappealing and hard to take seriously, when one is talking about such a striking difference between Homo sapiens and everything else, a difference predicated on a large brain that consumes a hefty portion of our daily caloric intake. The answer must lie elsewhere.

Maybe it was demographics: once our species reached a certain population threshold cultural information became less likely to be lost, and it started to accumulate. But as Laland quickly observes, there are plenty of other species with large population sizes, and they haven’t invented vaccines or drafted declarations of individual rights.

Instead, some tantalizing clues come from mathematical modeling exploring how many “cultural parents” are necessary for stable cultural transmission. The details are intriguing, and I refer the reader to the book chapter for much more, but the bottom line is that a small increase in the fidelity of social learning makes a huge difference for the stability of cultural traits, and beyond a certain threshold of fidelity it makes them essentially immortal. In turn, high-fidelity mechanisms simply support a far larger accumulation of cultural knowledge, over time. So a species’ repertoire becomes both more reliable and far larger.

Why primates, however, and humans in particular? Because, as it turns out, most other species operate on the basis of low fidelity cultural transmission, including birds, fishes, and insects. As a result, most animal species either have no cultural traditions at all, or are characterized by so-called “lightening traditions,” i.e., patterns that persist in a population only for an evolutionarily short period of time and then are lost, possibly re-invented, and lost again. No cumulative process there.

“Across thousands of simulations with different parameter values, trait fidelity explained more of the variance in the buildup of cumulative culture than novel invention, modification, and combination combined.” (p. 156)

One of the interesting, and perhaps counterintuitive, findings here is that innovation is the least important of the pertinent cultural traits. That’s because cultural evolution takes place largely through continuous, cumulative, alterations on previous designs, reworking and further developing pre-existing technology. The myth of the heroic inventor is, largely, a myth.

Not only that, but teaching — defined by Kevin as behavior that functions to enhance the fidelity of information transmission between tutor and pupil — turns out also to be a crucial factor in ever accelerating cultural evolution. Even though there is controversy about this point, there are precious few solidly documented cases of teaching outside the human species, while the behavior is universal — and in some cases highly refined — across human populations. Moreover, the known examples of animal teaching do not, in fact, show up where one would expect them to:

“Animal behaviorists have now compiled evidence for teaching in a small and rather curious assortment of species; these include meerkats, ants, bees, and two species of birds called pied babblers and superb fairy wrens; with suggestive, but not yet conclusive, evidence in cats, cheetahs, and tamarin monkeys. The functional similarities between teaching in, say, ants and humans should not [however] obscure the fact that mechanistically, cases of teaching in other animals are entirely different from human teaching, and are reliant on entirely separate psychological and neural processes. … We were struck by the observation that no compelling evidence for teaching had been found in nonhuman apes, dolphins, elephants, or other large-brained mammals celebrated for their intelligence.” (p. 161-162)

Some findings about teaching in the animal world — based on computer modeling — are intuitive, for instance that it is favored by selection the more tutor and pupil are genetically related to each other. But other findings are both counterintuitive and enlightening: teaching is favored when it concerns tasks of intermediate difficulty, not too easy, not too difficult. Why? Because if a task is very easy then the individual is likely to learn it on its own, no teaching required — which in turn explains why a lot of intelligent species do not engage in teaching. By contrast, if a task is too difficult, then there simply won’t be enough teachers available to transmit it efficiently to the next generation. Comparatively few traits are found in the right intermediate range of difficulty, which is probably a major part of the explanation for the rarity of teaching in nature. There is an important lesson to be learned here:

“The incidence of teaching only appeared puzzling because we had the wrong intuitions. We had expected teaching to be exhibited by clever animals that are good at social learning. In fact, with some caveats that we will come to, smart animals rarely need to teach, because most of their skills can be picked up through copying or trial and error.” (p. 165)

The attentive reader, however, will have picked up on the fact that human beings seem to flagrantly violate the above rules: we teach very, very complex behaviors indeed! Laland and his collaborators began to suspect that it was cumulative knowledge that had made the difference. Interestingly, once the mathematical models allowed for cumulative knowledge, the results clearly showed that teaching was favored, as the relative fitness of teachers to non-teachers was almost always higher under those circumstances:

“Models that allow for cumulative cultural knowledge gain, however, suggest that teaching evolved in humans despite, rather than because of, our strong imitative capabilities, and primarily because cumulative culture renders otherwise difficult-to-acquire valuable information available to teach. The analyses suggest that human teaching and cumulative culture evolved together, through mutual reinforcement.” (p. 167)

Yet another factor facilitating the evolution of teaching is cooperative breeding, when young ones are raised by a group of relatives, instead of just the parents, or one of the parents. That’s because cooperative breeding makes the fitness cost of being a teacher surprisingly low, thus favoring the behavior. Finally, experimental results show that human children far outperform other primates at cognitive tasks in part because they cooperate with each other in the solution of problems, engaging in a high number of “altruistic events” during the time a group is occupied with a given task. The conclusion, so far in the story, is then that:

“Humans alone possess cumulative culture because humans alone possess sufficiently high-fidelity information transmission mechanisms, including an unusually accurate capacity for imitation, teaching, and language.” (p. 174)

66 thoughts on “Book Club: Darwin’s Unfinished Symphony, 4, intelligence and high fidelity

  1. synred

    does Laland cover group teaching at all?

    I don’t think Laland mentions it (but it’s been awhile since I read it). I did see my cousin’s cat appearing to teach her kittens to stalk, but that ain’t science…


  2. brodix

    How much conscious activity is also instinctive? Pro-social behavior is certainly an aspect of herding and anti-social behavior is often likely due to sub-conscious impulse.

    How much is sub-consciousness a form of “other” consciousness, in the sense that just as some other person trying to get your attention is conscious, other parts of the mental process that are not dominant, are still aware, but effective neurological functioning tends to isolate as individual thought. Much as the sun obscures stars.
    Otherwise we would be schizophrenic.

    So, if both those points are logical, how much are we a larger organism, that functions as units? A hive mind, so to speak.


  3. brodix

    To further note, the capitalist/libertarian rejection/fear of communism/socialism is just that fear of the hive mind, yet the seeming alternative is an atomized culture, held together with bureaucratic institutions and a predatory financial system,. And Ayn Rand as the individualist ideal.
    Is there some organic whole we have lost with our quantification of every detail?


  4. Daniel Kaufman

    The way I would parse this is more along Robins lines. My arm shooting up in reaction to an attack is different from my raising my arm for a reason — like to ask a question. The first is more like the meerkat. Of course I would give a Wittgensteinian account if the difference rather than a mentalist one.

    Liked by 1 person

  5. synred

    I wonder if meerkats in addition to learning how to handle scorpions learn how to teach the handling of scorpions…

    “Those who can do, those who can’t teach” would not seem to apply…


  6. Daniel Kaufman

    The meerkat is complicated, because as a mammal, it may not be crazy to ascribe intentionality to its behavior (though I am very dubious about this). If we were talking about an insect or a shrimp, however, then it clearly would be absurd to do so.

    Liked by 1 person

  7. brodix

    Considering the concept of fidelity and its applications, say from teaching to saying prayers in church, that one is extremely conscious when one is acting instinctively. We are not only following the path laid out, but are doing our very best to re-enforce it.

    Those who might question the path would be considered anti-group by those true to it.

    Insert political chasms here.


  8. Robin Herbert


    “Robin do you mean meerkats aren’t conscious?”

    No, meerkats are clearly conscious. It’s just that I don’t think they say to themselves “It’s high time junior learned to eat scorpions safely”. As Massimo says it is not relevant so I won’t pursue it.

    Liked by 1 person

  9. Robin Herbert

    This part had me puzzled:

    Finally, experimental results show that human children far outperform other primates at cognitive tasks in part because they cooperate with each other in the solution of problems, engaging in a high number of “altruistic events” during the time a group is occupied with a given task.

    Given that even a two year old child with a mild to moderate intellectual disability is considerably smarter than the smartest adult in any other primate, I question the validity of the comparison. The children in the study are aged 3-4 (presumably neurotypical) and compared to adult chimpanzees and capuchin monkeys.

    The gap in general intelligence and ability to understand things would be vast.

    A human can understand that it is possible to get help for a task that they can’t work out on their own. It seems unlikely that a chimpanzee or capuchin monkey can understand this.

    Specifically, the human children were observed to focus on the actual actions of others. It seems likely to me that they focus on the actual actions of others because they understand that they can learn by doing so. It seems less likely that a general tendency to focus on the actual actions of others was a direct factor.

    I have described this situation before – a two year old child with a mild to moderate intellectual disability and no language is playing “Temple Run”. He can work out by trial and error how to jump over and swerve around things, but cannot work out how to slide under.

    So he goes to his older brother, takes his hand and holds it over the screen and then watches what his brother does. After a while he pushes away his brother’s hand and continues to play, now able to slide under obstacles.

    That is a clear case of the child having a need to learn something and understanding that in order to do so he will have to focus on the actions of others and works out how to make this happen.


  10. Massimo Post author


    Yes, even a very young human is far smarter than an adult chimpanzee. That’s part of the point. The comparison, however, wasn’t about smarts per se, but about the dynamics used by the two species to solve problems. Humans were far more cooperative and altruistic.


  11. SocraticGadfly

    Massimo, related to that, there is possibly one non-human species that shows a fair degree of cooperation — wolves. Corvids as a family do some of this, more than most birds, but less than humans for sure.

    There’s videos that show pictures of both wolves and dogs given a set of exercises that require two animals to work together intelligently to move an object that will give them food treats. Wolves do this MUCH quicker. I don’t know how much of this is domestication breeding this out of dogs or what.

    I offer that to note that, while cultural evolution built on our group learning, it of course had to have a biological template to work with.

    And also, with that, this is a HUGE illustration of Steve Gould’s contingency. Seeing you say a few weeks ago that Lewontin was a big biological influence for you, I assume Gould rubbed off somewhat, as you’ve generally favorably discussed him in the past.

    Liked by 1 person

  12. Massimo Post author


    Indeed, Kevin does mention corvids and other examples. But as he puts it, those are not the ones we would expect. And some of the latter (dolphins, chimpanzees) don’t show much cooperative learning or teaching.


  13. SocraticGadfly

    I had been thinking of cetaceans along with primates. Both, yes, seem to have some degree of group communication, but I didn’t think either exemplified much group learning. The one other animal I can think of that might have some kind of group learning would be elephants.


  14. Massimo Post author


    Actually no, elephants don’t show group learning either. They are explicitly mentioned in Kevin’s chapter. It really is surprising, but as he points out, that actually tells a lot about the evolution of learning.


  15. synred

    I had been thinking of cetaceans along with primates

    There is an article in SciAm on cetaceans and brain size vs. social interaction. I only have it in the paper addition, I haven’t been able to get at it online for some reason.


  16. Robin Herbert


    Yes, even a very young human is far smarter than an adult chimpanzee. That’s part of the point. The comparison, however, wasn’t about smarts per se, but about the dynamics used by the two species to solve problems. Humans were far more cooperative and altruistic.

    What I am suggesting is that the reason that chimpanzees and capuchin monkeys don’t use cooperative strategies to solve problems is that they are not smart enough to do so, and the reason we do use cooperative strategies is that we are smart enough.

    If that were the case then this would tell us nothing about how we got smart enough to use these strategies in the first place.

    I could play Devil’s Advocate with the whole thesis and suggest that the key factor in cultural accumulation is being smart enough to fit all of that knowledge together and the reason that chimpanzees don’t have a cultural accumulation is not that they don’t copy with sufficient fidelity but that they are not smart enough to fit the knowledge together. There would then arise a point at which more cultural traits would be dysfunctional for other primates.


  17. brodix

    Elephants, dolphins? Hard to invent technology with out the digits. Control fire?
    The fact primates evolved to swing around in trees is a convenient advantage. Not only does it give us the dexterity, but it also requires bifocal focus and object orientation. Like predators, but as much about navigation, as hunting.
    Having worked around horses and cattle, that having eyes on the sides of your head might help with spatial awareness, in order to avoid predators, but it doesn’t give you some of the basic mechanisms for tactical, projected planning.

    Liked by 1 person

  18. Massimo Post author


    You could play Devil’s Advocate. But your thesis would go straight against much of the empirical evidence and mathematical models that Kevin’s group has accumulated.


  19. Robin Herbert


    “You could play Devil’s Advocate. But your thesis would go straight against much of the empirical evidence and mathematical models that Kevin’s group has accumulated.”

    It is completely consistent the models and studies I have seen so far, admittedly I haven’t seen them all.

    Can you supply an example of a model which is inconsistent with the thesis that the key factor in cultural accumulation is the intelligence to fit knowledge together?


  20. Massimo Post author


    I suggest you read the chapter, the arguments and empirical evidence is laid out clearly and it would be cumbersome for me to repeat it here.


  21. synred

    “Can you supply an example of a model which is inconsistent with the thesis that the key factor in cultural accumulation is the intelligence”

    I think your model lacks the feed back cultural accumulation feedback mechanism that his Laland’s main point. I think I could put that in a simulation though not in analytic model.


  22. Robin Herbert


    I think your model lacks the feed back cultural accumulation feedback mechanism that his Laland’s main point. I think I could put that in a simulation though not in analytic model.

    I don’t have a model so much as an alternate interpretation of the data and as such is consistent with the cultural accumulation feedback.

    But the point is that cultural accumulation is not just a matter of building up a mountain of cultural traits, it is a matter of fitting them together properly. If capuchin monkeys or chimpanzees could build up many cultural traits over time they still could not invent so much as a wheel because they don’t have the mental acuity to fit the information together into a whole.

    Again, I would suggest that the driver behind copying fidelity that does not diminish as the number of cultural traits grows, is the ability to understand how those things fit together into a world view (even a mistaken but socially useful world view).


  23. Robin Herbert

    Off the top of my head, the way you would model this is to define traits as having a rank, where a de novo trait has rank 0, but a combination trait that depends on two or more de novo traits would have rank 1 and a trait that depends upon two or more rank 1 traits would have rank 2.

    Then there could be a factor by which copying fidelity falls as the rank increases, ie that transmission of a higher rank depends not only on the receiver having the lower level traits but also on the ability of the receiver to combine those traits into something new. So for example transmission fidelity might reduce 20%, or 50% with each rank.

    I would suggest that the development of a complex culture might depend more upon the the transmission fidelity being preserved as the rank rises than it does on the value you choose for transmission fidelity in the first place.


  24. wtc48

    The examples presenting a comparison of human and animal intelligence as a rule involve tests constructed by a human from a human point of view. A comparison, by contrast, of instinctive behavior vs. human (culturally informed) behavior would probably shift the balance in favor of instinct. For instance, a human attempting (without technological assistance) to construct a web, vs. a spider, would give the advantage to the spider. As Robin suggests, it is the ability to operate across an enormous spectrum of traits that gives humans their advantage, even though trait by trait, there may always be some animal that would show us up easily. Humans are nature’s great generalists.

    Liked by 1 person

  25. brodix


    Do we really understand how it fits together?… religion…chemistry….sexes…. television…history…Trump…money…..pets….states….cellphones…children….drugs….photography…work…coffee…potato chips….holidays….

    It seems the more we know, the more we know we don’t know. We build it up, take it for granted and then it falls apart. Did we really know, or is it just forward momentum and we keep patching the gaps with stories, knowledge, bull$hit, rationalization, or just go onto the next news cycle.

    We go in these circles and think it fits together, but we never seem to get to the end of the circle, other than dying.


  26. brodix

    Says something for generalists. That’s why generals run armies and specialist is an enlisted rank.
    Maybe something for philosophers to think about, when they are trying to figure out on what to focus.


  27. Alan White

    Brodix, one correction for philosophers, at least as professionals. The specialists are often rewarded handsomely for narrowness and productivity therein; generalists (at least teaching generalists) not so much. I just saw a link to a top philosopher (younger than I) at a major institution who I once chaired a session for, showing up in a tee-shirt (because his luggage was lost–not his fault), and because he published lights-out in that general area, now pulls down 300K a year. I’m retiring as a senior philosopher at my generalist teaching institution–with some of my own accolades that pushed my salary upwards to be near the top of my institution–at 70K. What happens in philosophy is that if someone does the specialist thing and gets notoriety, only then may they generalize and spread out and get recognized as “having wide interests”. For professional success, specialization is where it’s at.


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