Tag Archives: Darwin Unfinished Symphony

Book Club: Darwin’s Unfinished Symphony, 9, the arts

painting elephants“The logic of cultural evolution is identical to that of biological evolution, even if the details differ. New ideas, behaviors, or products are devised through diverse creative processes; these differ in their attractiveness, appeal, or utility, and as a result are differentially adopted, with newfangled variants superseding the obsolete,” says Kevin Laland at the beginning of the last chapter of his book, Darwin’s Unfinished Symphony: How Culture Made the Human Mind (p. 292). It is, therefore, with a brief commentary on this chapter, focusing on the arts, that I will end my series on Kevin’s fascinating view of the young field of cultural evolution.

That introductory gambit actually illustrates where Laland’s and my views begin to diverge, though perhaps not as sharply as each of our perspectives differs from standard evolutionary psychology. I see cultural evolution as linked to its biological counterpart in two ways: first, because it originated from it; and second, because there is a broad analogy between the two. But I fall far short of Kevin’s strong statement that the two are “identical” in logic. They are not, in my mind, fundamentally because biological evolution is propelled by the teolonomic process of natural selection. Cultural evolution, by contrast, is moved by the teleological process of human cognition. The two are not the same, and I maintain that no currently available theory of cultural evolution satisfactorily accounts for either the difference or the relationship between the two. (I hasten to say, which should not be necessary, that I see nothing magical or “mysterian” about this. At all. It is simply an open scientific question, like many others.)

The cultural evolution of art is, obviously, a huge topic, which would require a book of its own. So Laland takes a reasonable approach, focusing on aspects of the evolution of a particular art form: dance. As we shall see, he has lots of interesting things to say, but not much that would surprise a historian of dance, and definitely not much that originates specifically from a biological evolutionary perspective.

Before getting to dancing, Kevin briefly discusses another art form, acting, making the case that it crucially (though not solely, of course) depends on imitation, which he has argued previously, is an important evolved skill in the human lineage. Since dancing also fully deploys our ability to imitate others, and given that neither acting nor dancing presumably were direct targets of natural selection, he can then conclude that both art forms are in fact a byproduct of natural selection for the capacity to imitate.

“Imitation is no trivial matter. Few other animals are capable of motor imitation, and even those that do exhibit this form of learning cannot imitate with anything like the accuracy and precision of our species.” (p. 295)

Our ancestors at some point became able to solve what Laland calls the correspondence problem: imagine, for instance, that you are trying to learn how to use chopsticks. This is done by imitation, which requires translating the visual cues obtained by watching someone using chopsticks into the motor control that our own muscles have to exercise in order for us to be able to do the same. The sensory experiences involved in watching and doing are utterly different, and yet somehow our brain has to be capable to solve this correspondence problem.

Recent research has shown that human beings solve the correspondence problem by using neural networks similar to the so-called mirror neurons discovered in other primates. Kevin suggests that it is plausible that the mirror neuron or equivalent network has been selected precisely to facilitate imitation, that this particular skill has been much more refined by natural selection in humans, and that one of its most astounding and least recognized byproducts is our ability to do and appreciate art — not just movies and dancing, but also painting, sculpture, theater, music, and even computer gaming.

Kevin doesn’t think much of the alleged ability of other animals to produce art, and I think he is right:

“The motor control that allows humans to produce artistic works and performances spontaneously is a capability that no other animal shares. … The claim that chimpanzees [for instance] are artists, in any meaningful sense, is greeted with skepticism by animal behaviorists and art scholars alike.” (p. 299)

He also thoroughly debunks the idea that elephants in Thailand can paint, referring instead to evidence that the animals have been well trained to respond to subtle cues provided by their handlers, through the simple device of tugging at the elephant’s ears.

What about dancing? Here again the suggestion has been made that some animals do it, though as Laland points out, much of the answer depends on how one defines dancing, and what counts as instances of the art form. Regardless, and more importantly, he highlights the fact that the only good candidates for dancing animals are, not surprisingly, those species that are most capable of imitation. (The same considerations apply to singing animals, by the way.)

“The most transparent connection between dance and imitation … will be readily apparent to just about anyone who has ever taken or observed a dance lesson; that is, dance sequences are typically learned through imitation. … It is no coincidence that dance rehearsal studios around the world almost always have large mirrors along one wall. These allow the learner to flit rapidly between observing the movements of the instructor or choreographer and observing their own performance.” (p. 307-308)

The other thing that makes for a good dancer is the ability to learn a long sequence of actions, and Kevin has shown before in the book that this type of learning is very difficult in a non-social setting, because it pretty much requires teachers. So the evolution of teaching, which he has discussed previously as a crucial component of early cultural evolution in the human lineage, is also a prerequisite for the wonderful byproduct of our biology that we call dance.

Much of the remainder of the chapter concerns itself with the history of dancing, and it is there, I think, that the limits of insights from biological evolution are most painfully clear. Laland asks whether dance could be said to have evolved in any “rigorous” sense of the term, by which he means to ask whether dance as a “system” possesses the characteristics that any evolving system has to possess: variation, differential fitness, and inheritance. But it should be obvious that while the evolution of dance does display all three, we have essentially no account whatsoever of the second element, differential fitness. This deficiency, I argue, at the moment makes cultural evolution into a tautological theory of the kind that Karl Popper (mistakenly) thought the theory of biological evolution was. While Darwin and his successors solved that problem in the biological case, neither evolutionary psychologists nor the more sophisticated approach advocated by Kevin and colleagues has been able to solve it in the case of cultural evolution.

Kevin presents readers with a number of examples showing that there is much variation among the world’s dances, and that this variation is culturally inherited via imitation (though, crucially, the equivalent of biological “mutation” and “recombination” result from conscious or unconscious human decision making, which follows, and indeed also shapes, human aesthetic judgments).

We therefore learn about European sword dances, which apparently first appeared in ancient Greece and were brought to Britain by invading Danes and Vikings. Waltz is Kevin’s favorite example of cultural fitness, as he calls it. And yet, here the limits of his approach are stark, in his own words:

“Relative to other dances in the late eighteenth century, the waltz could be said to possess high ‘cultural fitness,’ which really means little more than it was unusually appealing and as a result increased readily in frequency.” (p. 311)

Right. And that, right there, is the problem. Strip the fancy wording and we are left with: “waltz (at that particular time, in that particular culture) had high fitness because it had high fitness.” That’s the sort of vicious circularity that rightly annoyed Popper. You don’t find it in evolutionary biology because a separate discipline comes to the rescue: functional ecology. It is the latter that allows us to make predictions about which organismal traits are going to be adaptive in one environment or another, given the organism’s anatomy, physiology, and ecology (and given the laws of physics and chemistry). We don’t just say that natural selection favors the fit, and then immediately turn around and define the fit as those that are favored by natural selection. But that’s pretty much what cultural evolutionary theory does, at the moment, and it shares this limitation with other approaches, such as evolutionary psychology and memetics, though for different reasons that are specific to each approach.

To be fair, Kevin does attempt to sketch an elementary functional ecology of dance. For instance we are told that waltz was attractive in late 18th century Europe, in part because of the “dance’s intoxicating swirling, and the dangerously intimate contact between male and female were a major draw.”

Okay, but presumably swirling and close male and female contact have always been intoxicating. So why late 18th century Europe? Moreover, I don’t know much about the history of dance as an academic field of study, but I doubt anything Laland says in this chapter will come as a surprise to historians of dance — and I mean everything, from the genealogical patterns of evolution by imitation to the “mutations” introduced by different cultures at different times, to ad hoc explanations (which may even be true) like the intoxicating effect of a particular dance. In other words, invoking Darwin here does no work at all, or almost.

I don’t have a better alternative. I chose Kevin’s book precisely because I think it is one of the best in the field of cultural evolution, reflecting the incredible vigor and ingenuity of Kevin as a principal investigator, not to mention the many collaborators he gives due credit throughout the book. It’s all tantalizing and very, very interesting. But it falls far short of a comprehensive theory of cultural evolution. It is good to learn about the importance of social learning, of teaching, and of imitation throughout the history of hominins. It is fascinating to think that such biological history has a lot to do with the subsequent shaping of cultural evolution. But we are still nowhere near giving a decent scientific account of sword dancing, waltz, flamenco, polka, jitterbug, or rock’n’roll. Not to mention Michelangelo, Picasso, and de Kooning; or Mozart, Beethoven and Tchaikovsky; or Homer, Dante, and Shakespeare. And so on and so forth, encompassing the bewildering variety of manifestations of what we call culture.

_____

And now for something completely different: our next book will be Early Socratic Dialogues, edited by Trevor J. Saunders, Penguin 2005. I figured that this is a blog called Footnotes to Plato, and yet we have hardly talked about Plato. So, here we go…

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Book Club: Darwin’s Unfinished Symphony, 8, foundations of cooperation

reciprocal altruismThink about the complexities involved in allowing you to do something that nowadays is fairly normal: getting on a plane and fly to another city, across an ocean. It’s not just the sophisticated machinery, ground transportation, the airports, and so forth. It’s the people. Accomplishing such a feat requires the coordinated cooperation of a large number of people who don’t know each other, and don’t know you or why you wish to get on that plane in the first place. This observation sets the stage for the next to the last chapter of Kevin Laland’s Darwin’s Unfinished Symphony: How Culture Made the Human Mind, which we have been discussing for a while now.

The first point Kevin makes in this chapter (n. 11 in the book) is that conventional evolutionary explanations, such as kin selection and other gene-based explanations are insufficient to account for the degree and sophistication of cooperative activities that have characterized human civilization ever since the agricultural revolution. A fully formed theory of cultural evolution is needed, to draw the outlines of which, of course, is Kevin’s goal. Obviously, the idea is not that cultural evolution is independent from its biological counterpart, but rather that it is a novel mode of evolutionary change that resulted from the particular path of biological evolution that hominins happen to have taken.

Two of the factors that make large-scale human cooperation possible are the ability to teach others, and language, which Laland has already argued itself evolved to facilitate teaching. A third factor was the origin of social norms. These specify how individuals are expected to behave within a group, including how to treat individuals who violate norms. Crucially, norms also make possible for people to identify with a particular group, as abiding by its norms carries privileges for in-group members.

Moreover, humans are pretty much the only animals capable of trading goods (there are a few alleged cases in other primates, but they are disputed), and certainly the only ones that arrived at that convenient abstraction we call money. This level of sophistication requires language, and it is both facilitated and made necessary by the existence of division of labor, something that evolved to a high degree of sophistication, again, after the agricultural revolution, which made possible the existence of large and stable groups of humans.

All of this coordination is beneficial thanks to the advantage provided to individuals by indirect reciprocity: I do something for you, you do something for someone else, and at some point down the line another person that has been benefiting from in-group membership does something for me. Like allowing me to safely cross the Atlantic to get from New York to Rome. Repeated bouts of indirect reciprocity require gossip, so that people have a sense of who they can trust and who to stay away from. Needless to say, gossiping, and hence the building and destroying of social reputations, is not possible, again, without language.

Language, in turn, also evolves, quickly generating local dialects. Dialects then rapidly become a mark of local membership, a quick heuristic to tell apart in- from out-group members. They increase within-group cooperation, and likely across-group conflict, which sets the stage for group selection at the cultural level:

“Cultural processes generate plenty of variation among human groups for natural selection to act upon. Extensive data now demonstrate that the differences between human societies result far more from cultural rather than genetic variation. … Symbolic group marker systems, such as rituals, dances, songs, languages, dress, and flags, make it considerably easier for cultures to maintain their identities and to resist imported cultural traits from immigrants, than it is for local gene pools to maintain their identity by resisting gene flow.” (p. 283)

This is something important to keep in mind, as it is intuitive to say that cultures change more rapidly than genes. While this is true if we are talking about mutations (which are, indeed, rare), it is not the case once we consider gene flow and genetic recombination, which happen far more frequently, as Kevin points out, than some types of cultural change.

Laland also remarks on the widespread existence of practices that synchronize the behavior of individuals, like group dancing, or military marches. These activities result in the simultaneous release of endorphins, which in turn promotes within-group bonding. The broader point is that humans evolved a psychology of group behavior that is entirely unknown in other animals, and that cannot be explained on the basis of standard genetic models of evolution. Pace the evolutionary psychologists, of course, for whom we have seen Laland has relatively little patience.

We are reaching the end of this series of posts on Darwin’s Unfinished Symphony. The next and last installment will focus on the cultural evolutionary origin and significance of art.

Book Club: Darwin’s Unfinished Symphony, 7, the dawn of civilization

Egyptian agricultureHomo sapiens is the only species on planet Earth to have experienced three phases of evolution: the standard biological one, driven by mutation and natural selection; gene-culture coevolution; and now the period of evolution driven primarily by culture. This is how chapter 10 of Kevin Laland’s Darwin’s Unfinished Symphony: How Culture Made the Human Mind, begins the transition to the author’s discussion of that very last, novel, and crucial phase. (More entries in this ongoing series here.)

It’s an obviously crucial topic for a variety of reasons. First off, to help explain why on earth we evolved such large and metabolically expensive brains. Keep in mind that the human brain accounts for only 2% of our total body weight, and yet it consumes a whopping 20% of our daily caloric intake. (It’s unfortunate that thinking harder doesn’t lead to weight loss…). Second, as Kevin has documented in the previous chapters of the book, it is our capacity for social learning (and teaching) that accounts for the incredible success of our species, as the third mode of evolution is what has made possible for us to build giant cities, go to the Moon, and waste our existence on social media.

Kevin begins by addressing a related question: why did it take so long for our species to develop complex civilizations, while hunter-gatherer societies still today have very limited technology and simple cultures? The likely answer has to do with the severe limitations imposed by a hunter-gatherer lifestyle. To begin with, of course, hunter-gatherers have to be constantly on the move, changing base location once the local resources are depleted. This means that it is impossible to settle down long enough to develop a large population size and the division of labor that foster new technological developments. And even if some new technology were to be developed, it would have to be of limited size and complexity, again because the entire population has to pick up and move every few weeks or so.

Similarly, in hunter-gatherer societies the birthrate is typically low, with new pregnancies well separated in time, as a human female cannot carry and care for many small children when the group is constantly on the move. Small population size and temporary abodes also means no accumulation of wealth of the kind that makes division of labor possible, leading in turn to the origin of specialized classes of workers that can rapidly accumulate specific technical knowledge over few generations.

“This helps us understand why hunter-gather technology was only slowly changing for such a long time, and also why, even today, many small-scale societies possess limited technology. Hunter-gatherers are effectively trapped in a vicious cycle that severely constrains their rate of cultural evolution.” (p. 248)

That’s also why the invention of agriculture, which took place multiple times after the last Ice Age, is tightly linked with the origin of complex human technological cultures. The reason agriculture did not originate earlier is because the conditions following that Ice Age, about 11,500 years ago, have actually been the most favorable — climatically speaking — for such an event over the last two million years of hominid evolution. And before then our ancestors simply did not have the required brain power and ability to communicate through language.

Plant and animal domestication of some sort preceded the full blown agriculture revolution, and the first plants to be domesticated were annuals, characterized by a rapid life cycle and hence easy to select artificially. These included peas, wheat, rye, barley, and maize. A new form of wheat, for instance, appeared around 9,600 BCE in the eastern Mediterranean region. Maize was farmed in southern Mexico around 9,000 years ago. Millet appeared in China between 10,300 and 8,700 years ago, rice around 9,000 years ago.

The invention of agriculture was not without its own problems. The more stable source of food led to population explosions, which in turn caused periodical famines. Indeed, the archeological data show that Europeans became shorter by about 7 cm. between 2,300 and as little as 400 years ago, because of poor nutrition.

As Laland points out, agriculture is a great example of niche construction on the part of human beings. The old idea, in ecology, that niches are “out there,” waiting to be filled by new species of organisms, has been questioned for some time now. Rather, living beings actively alter their environment, co-evolving with it, if you will. By far the most spectacular example in the history of earth is the fact that we have high levels of oxygen in our atmosphere, a byproduct of photosynthesis, an organic process that has made animal life possible in the first place.

Since agriculture was not an unqualified good, it is reasonable to ask how come the new mode of life largely and rapidly replaced the old hunter-gathering. Kevin offers two main reasons: first, agriculturalists simply outbred hunter-gatherers, because of the larger population size made possible by a sedentary lifestyle. Before the advent of agriculture the world’s human population had stabilized at around one million people. By the time of the Roman empire it was up to 60 millions.

The second factor was a wave of innovations triggered by agriculture. For instance, the invention of the wheel, which appeared simultaneously in Mesopotamia, Russia and central Europe around 5,500 years ago. The first organized religions also sprang in agricultural societies, with different cultures, predictably, worshiping gods related to agriculture: Inti, the sun-god of the Inca; Renenutet, the Egyptian god of harvest; Ashnan, the goddess of grain in Mesopotamia; and Ceres, the Roman goddess (counterpart of the Greek Demeter) who was credited with the discovery of wheat, the invention of ploughing, the yoking of oxen, and similar.

Here is another way to appreciate the difference between pre- and post-agriculture humanity:

“Prior to the advent of agriculture, each population would have possessed at most a few hundred types of artifacts, while today the inhabitants of New York are able to choose between 100 billion bar-coded items. … One recent estimate of the amount of information now stored on the internet is 1,200,000 terabytes.” (p. 263, 269)

Kevin points out that all this innovation has had dark sides, including environmental destruction, not just today, but throughout the last 10,000 years or so, with humanity being responsible for countless extinctions of other species; as well as of course the scale of war that technology has made possible; and the increasing inequality (compared to hunter-gatherer societies) among human beings themselves. It seems like both natural and cultural selection don’t really care about ethical considerations, although of course we should. But that’s another story.

Book Club: Darwin’s Unfinished Symphony, 6, gene-culture co-evolution

lactose tolerance

map of lactose tolerance

Kevin Laland’s book, Darwin’s Unfinished Symphony, which I have been discussing for several posts now, is basically one long argument in favor of the thesis that human evolution has been shaped by a feedback process involving a cultural drive mechanism initiated by natural selection, a mechanism that favored the acquisition of accurate and efficient copying. Chapter 9, to be examined here, is devoted to the classic approach of gene-culture co-evolution, the fundamental notion that cultural changes affect genetic evolution, and indeed that the more time passes the more human evolution is increasingly driven by culture and less so by biology (though biology always remains a fundamental constraint to be reckoned with):

“Genetic propensities, expressed throughout development, influence the cultural traits that are learned, while cultural knowledge, expressed in behavior and artifacts, spreads through populations and modifies how natural selection affects human populations in repeated, richly interwoven interactions.” (p. 217)

While the chapter begins with an interesting treatment of the phenomenon of right-handedness, the standard example of gene-culture co-evolution is, of course, lactose tolerance. In most humans, the ability to metabolize milk disappears in adulthood, as it was not pre-historically needed. But some populations have large numbers of adult individuals that retain a functional version of the gene coding for lactase activity, resulting in the phenotype of lactose tolerance. We now know that lactose tolerance evolved independently at least six times, and that this happened after the switch to agriculture following the last glaciation, making it a strong candidate for culture-driven genetic change in humans. Interestingly, mathematical models show that the rapidity of spread of the genetic trait depends on the fidelity of transmission of the cultural one: the more likely children of milk drinkers are to become milk drinkers themselves, the stronger the selection coefficient favoring the continued expression of the lactase gene into adulthood.

Several other traits have been shown to have evolved in a similar fashion in recent human history, including genes involved in skin pigmentation, salt retention, and heat stress, all obviously related to the sorts of climate changes experienced by human populations during their migrations. Unfortunately for us today, some of these strongly selected genes facilitate a highly efficient usage of food sources, as well as storage of energy into fats. Hence the trouble that many moderns are experiencing with obesity, leading to diabetes and heart problems, among other negative effects. Another fascinating example is the sarcomeric myosin gene MYH16, expressed mostly in the jawbone. A sizable chunk of the gene has been deleted, leading hominins to lose a lot of jaw muscles. This genetic event occurred at about the time we invented cooking, which made strong jaw muscles unnecessary (and likely metabolically expensive). And of course, many genes involved with brain development, particularly the neocortex, are now known to have undergone very strong positive selection in recent time.

As Kevin is careful to point out, none of this means that natural selection stopped working in humans. So long as there will be differential survival and reproduction, selection will be active on our genomes. But its mode and tempo have been dramatically altered by the onset of cultural evolution, which has become a drive, rather than an outcome, of natural selection in our species. As Laland puts it:

“Theoretical models consistently find that gene-culture dynamics are typically faster, stronger, and operate over a broader range of conditions than conventional evolutionary dynamics. … This picture of the evolution of the human mind is radically different from the portrayal advanced by evolutionary psychologists and many popular science writers.” (p. 239)

I think Kevin is a bit too mild when he discusses the limitations of evolutionary psychology (whose initial central hypothesis, a massive modularity of the human mind, has now been definitively rejected empirically). He states that current research in gene-culture co-evolution shows that the degree of mismatch between our genetic endowment and our culturally created environment is “far more limited” than evopsych authors envisioned. I’d say that’s a dramatic understatement, but certainly still an observation that should lead serious evolutionary psychologists to revise a great deal of what they are doing, abandoning the increasingly silly idea that the Pleistocene was a crucial “environment of evolutionary adaptedness” (EEA), as if the genetic evolution of Homo sapiens had suddenly stopped at that point in time.

“Far from being trapped in the past by an outdated biological legacy, humans are characterized by a remarkable plasticity. Our adaptiveness is reinforced by both cultural and biological evolution.” (p. 240)

If people who write about evopsych were to take this conclusion a bit more seriously, especially when they write for a general public, there would be a lot less garbage floating around the pop science literature. But I ain’t holding my breath…

Book Club: Darwin’s Unfinished Symphony, 5, the evolution of language

LanguageWhy is it that only the species Homo sapiens has evolved language? Well, aside, possibly, for other, now extinct, species of our own genus. Despite much talk of animal communication, that’s just what other species do: communicate. Language is a very special, and highly sophisticated, type of communication. Characterized by grammar, capable of recursivity, inherently open ended. Nothing like that exists anywhere else in the animal world. Why?

That’s the topic of the eight chapter of Kevin Laland’s Darwin’s Unfinished Symphony: How Culture Made the Human Mind, which we are in the midst of discussing. A major problem here, as Laland points out, is not that we have no idea of the possible answer, but rather that there are too many explanations on offer, none of which seems to quite do the job. Here is a partial list. Language evolved:

  • To facilitate cooperative hunting.
  • As a costly ornament allowing females to assess male quality.
  • As a substitute for the grooming exhibited by other primate species.
  • To promote pair bonding.
  • To aid mother-child communication.
  • To gossip about others.
  • To expedite tool making.
  • As a tool for thought.

And of course it’s very possible that language evolved to fulfill more than one, or even all of those functions! The stumbling block isn’t the imagination of researchers, but rather the dearth of relevant empirical evidence (something, of course, that isn’t the case only in some areas of evolutionary biology).

Part of the difficulty stems from the fact that the evolution of language was a singular event, which precludes the use of one of evolutionary biology’s standard tools of investigation, the comparative phylogenetic method. Moreover, languages don’t leave much of a fossil record, thus taking out a second major tool from the biologist’s box.

Kevin proceeds by listing six criteria (and adding a seventh of his own) that a successful theory of language’s origin should meet in order to be further considered (I refer the reader to the chapter itself for more in-depth explanations concerning each criterion):

  1. The theory must account for the honesty of early language. (If words are easy and cost-free, why should anyone believe what others say?)
  2. The theory should account for the cooperativeness of early language. (Why should people, early on, have gone out of their way to help others by passing to them valuable information?)
  3. The theory should explain how language was adaptive from the onset. (As it is hard to imagine how it could have been a spandrel.)
  4. The concepts proposed by the theory should be grounded in reality. (That is, how did words acquire meaning in the first place?)
  5. The theory should explain the generality of language. (As opposed to the specificity characteristic of every other animal communication system.)
  6. The theory should account for the uniqueness of human language. (Why us and not anyone else?)
  7. The theory should explain why communication needed to be learned. (Why is it that language needed to be socially learned and capable of changing rapidly?)

Laland then concludes that no theory suggested so far meets all seven of these criteria, and I think he’s right. His preferred answer should, at this point in our discussion of the book, come as no surprise:

“[This] raises the question of why humans alone should exhibit a culture that ratchets up in complexity. Theoretical studies answer this question by showing that high-fidelity information transmission is necessary for cumulative culture, but then pose the supplementary question of how our ancestors achieved high-fidelity transmission. The obvious answer is through teaching.” (p. 183)

Kevin then proceeds in orderly fashion by comparing his preferred hypothesis — that language evolved in order to teach relatives — to the seven criteria just listed, finding that the language-to-teach scenario satisfies all of them.

At this point it will be good to step back for a second. To begin with, I’m sure that other students of the evolution of language will dispute both of Laland’s claims: (i) that no other hypothesis is a good fit for all seven criteria, and (ii) that only the language-to-teach hypothesis does a good job with the same criteria. Or perhaps (iii) someone will question the adequacy or necessity of one or more of the criteria in the first place.

For me, though, what makes this chapter the least convincing of those we have read so far is that even if we grant Kevin everything he is arguing for, we are still left, at best, with an hypothetical scenario that falls far short of empirical verification. Yes, maybe language evolved so that we could efficiently teach valuable information to our relatives, and things then went on from there. Or maybe there is a clever variant of one of the other hypotheses now on the table that will be even more convincing than the present analysis. Or perhaps there is yet another scenario that simply nobody has thought up yet. We just don’t know. And to be honest I don’t think we are likely to know any time soon, if ever. Precisely because of a major stumbling block acknowledged by Laland himself: the evolution of language was a unique historical event, and unique historical events are exceedingly difficult (though not impossible) to study.

While reading the chapter, I was reminded of some sharp, and I’m sure very much unwelcome words written by one of my scientific role models, the Harvard geneticist Richard Lewontin. In a book chapter entitled “The evolution of cognition: questions we will never answer,” he presents a critical analysis of the literature on the topic, making an argument that builds up to the following conclusion:

“I must say that the best lesson our readers can learn is to give up the childish notion that everything that is interesting about nature can be understood. History, and evolution is a form of history, [often] simply does not leave sufficient traces. … Form and even behavior may leave fossil remains, but forces like natural selection do not. It might be interesting to know how cognition (whatever that is) arose and spread and changed, but we cannot know. Tough luck.” (p. 130)

Seems to me that one could easily replace “cognition” with “language” and still be largely in the right. I’m sure Kevin will disagree, and I look forward to his comments.

_____

(Note to the reader: this commentary covers that major part of chapter 8, devoted to the question of the original function of language. The latter part of the chapter addresses a different, if related, question: how was it computationally possible for hominins to learn language, regardless of which selective pressured favored it? While interesting, I elected not to cover this bit, in order to focus discussion on what I think are the more crucial points of the chapter.)

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)

Book Club: Darwin’s Unfinished Symphony, 3, fish tales and creativity

Threespine and Ninespine sticklebacks

Continuing our discussion of Kevin Laland’s Darwin’s Unfinished Symphony, on the evolution of culture, I am going to briefly cover “A tale of two fishes” (ch. 4) and “The roots of creativity” (ch. 5). Together with the chapters we have already discussed, they complete the first part of the book, devoted to the foundations of culture. (After this, we’ll move to the chapters in the second part, on the evolution of the mind.)

Chapter 4 is devoted primarily to research conducted over a period of two decades by Laland’s own lab, focusing on the contrast in the behavior between two small species of fish, the threespine and the ninespine sticklebacks. The reason for working on this sort of experimental animals is that if one is interested in social evolution then one needs to set up replicates of entire populations. Logistically, this is going to be impossible to do for large vertebrates, especially mammals, but it is eminently feasible with fish. Sticklebacks are a well studied group of 16 related species, common in rivers, streams and coastal regions of the Northern hemisphere. Evolutionarily speaking, they are closely related to seahorses.

Laland’s lab focused on sticklebacks’ use of public information, i.e., on how they socially learn from other members of their own or even of other species. When they started the research project, the consensus was that use of public information required a high degree of intelligence on the part of the animal. It turns out that was definitely not the case, thus providing another important piece of the cultural evolution puzzle. Chapter 4 details lots of fascinating experiments with these two species of sticklebacks, but I will summarize only the basic stuff, leaving it to the interested reader to dig deeper.

The basic setup is one in which an aquarium is divided into compartments. In one area some fish of either species are being fed at a high rate (“rich patch”); in a second one they are being fed at a lower rate (“poor patch”); and in a third one they can observe their fellow species members feeding before being allowed to do so themselves: “if the sticklebacks were capable of public-information use, they would be able to distinguish between the rich and the poor patch based solely on the reactions of the demonstrators to the food.” (p. 80).

Interestingly, the ninespine was apparently able to use public information and, when allowed access, swim preferentially to the rich patch. The threespine, by contrast, showed no preference, indicating that the observers in that species had not learned from the demonstrators. Why the difference?

Laland’s group performed several follow-up experiments aimed at eliminating a number of simple explanations, such as that perhaps the demonstrators of one species were not as good as the demonstrators of the other, or that there was an inter-specific difference in the visual acuity of the fish, or maybe some of the relevant cues were olfactory, not just visual. None of that was the case.

“We began to believe that what we had discovered might genuinely be an adaptive specialization in social learning, with ninespines capable of exploiting public information, while their close relatives, the threespines, were not.” (p. 81)

The answer turned out to have to do with the relative cost of social and asocial learning. The cost of asocial learning is different for the two species, because of differences in their anatomical structures. The threespine stickleback has large spines, which are very effective against predation, so much so that often the fish gets stuck into the predator’s mouth, and is forcefully rejected instead of being eaten. This is not the case with the ninespine stickleback, whose spines are more numerous but much smaller and less robust, and therefore not as effective an anti-predator device. Threespines don’t need to engage in public information use because they can afford to explore the various patches and learn on their own. That approach, by contrast, is very dangerous for the ninespines, which accordingly evolved the more advantageous habit of learning socially by observing others. Interestingly:

“The ninespines’ behavior is precisely that predicted by a sophisticated evolutionary game theory analysis conducted by an economist in order to understand human behavior.” (p. 89)

Moreover, comparative research conducted on 50 populations sampled from 8 species belonging to 5 genera showed that only the ninespine and their closest relative, the brooks sticklebacks, are capable of public information use, thus demonstrating the intricate relationship between evolutionary history, ecology, and morphology in shaping cultural evolution.

Chapter 5 of Darwin’s Unfinished Symphony opens with the classic example of animal learning and cultural spreading: the invention of a method to open home delivered milk bottles by blue tit birds back in 1921 England. The instance is well documented, and because of the involvement of amateur ornithologists, we know how quickly and how far it spread, eventually to involve several species other than the blue tits. Interestingly, the “invention” appeared to be relatively easy to come by, so that a number of animals arrived at the same solution independently, not necessarily relying on copying public information. So milk bottle opening is a good example of innovation, the devising of a solution to a new problem posed by the environment.

Things like the milk bottle opening clearly show that human beings do not have a monopoly on creativity, though Laland immediately qualifies this by remind his readers that:

“A vast difference exists between dipping food and inventing a microwave cooker, while banging cans together to send a message is a long way from developing e-mail.” (p. 100)

Still, studying innovation is crucial to understanding human creativity and cultural evolution, and it is not easy because it is difficult to recognize a behavior as innovative unless one has a solid baseline of studies on pre-innovation behaviors in whatever species of interest.

One of the classical studies on animal innovation was conducted by Edward Thorndike at Columbia University. He confined cats in small boxes from which it was difficult, but not impossible, to escape. This was something the cats clearly disliked, to put it mildly. Thorndike was able to show that cats — once they learn how to get out of the box — fine tune their behavior so that the escape becomes easier and easier. The interesting part was that the animals arrive at suitable solutions by trying out a bunch of seemingly random moves, until something happens to work, even sub-optimally. It’s innovation by trial and error, very much something human beings do quite well.

One of the most interesting things about this chapter is Laland’s detailed presentation of evidence that, as the saying goes, “necessity is the mother of invention,” meaning that innovations are triggered by new challenges faced by animals, often under unusual or novel environmental conditions. Moreover, studies in callitrichid monkeys clearly showed that it is often the older, more experienced, individuals that come up with innovative behaviors, not the young ones, who are presumably insufficiently experienced to have mastered the problems posed by their environment.

While experiments with mammals, and especially primates, are of course the most fascinating, as pointed out above, they are both logistically challenging and expensive. Hence, again, the use of fish, which are much easier to raise and manipulate in statistically sufficient numbers.

Laland then describes a series of experiments his lab has conducted on another common fish, familiar to aquarium enthusiasts: guppies. The results were fascinating:

“Innovators were significantly more likely to be females than males, more likely to be food deprived than not, and typically smaller rather than larger fish. … The observed patterns are best explained by differences among fish in their motivational state. The first individuals to solve the [problem posed by the experimenter] are those driven to find novel foraging solutions by hunger, or by the metabolic costs of growth, or pregnancy [hence the predominance of females among innovators].” (p. 112)

Research on birds yields equally tantalizing clues. For one thing, species of birds that are more capable of innovation tend to be the ones whose populations survive when introduced into a new environment. Moreover, migratory species are less likely to be innovators than non-migrant ones, apparently because they are not as capable of introducing innovations in order to cope with their environment. If you can’t thrive in a given place, then change place, seems to be the idea. So migration turns out to be an evolutionarily alternative strategy to the option of staying and coping + innovating. Finally, innovative species of birds are more likely to speciate, i.e., to give origin to new species.

Though it is difficult to carry out systematic experiments on primates, it is possible to canvass the extensive literature on primatology, searching for and categorizing examples of innovative behaviors. Laland did this with one of his collaborators, Simon Reader. They found that:

“Consistent with our hypothesis that necessity was the mother of much animal innovation (derived from our fish experiments), across all primates [we] found more reported incidences of innovation in low-status individuals and fewer reports of innovation in high-status individuals than expected in either, given their numbers in the populations. … [We] found that approximately half of the instances of innovation that had taken place among primates had followed some sort of ecological challenge, such as a period of food shortage, a dry season, or habitat degradation.” (pp. 116-117)

And here is the kicker: controlling for phylogenetic relatedness, there is a very strong correlation between a tendency of a species to innovate and both its relative and absolute brain size. This, however, led to a puzzle: while the obvious conclusion to be drawn is that intelligence (measured by brain size as a proxy) has been favored in certain lineages in order to facilitate social learning and innovation, it is also true that several small-brained species — from fruit flies to fish — are capable of both. Why, then, evolve large brains to begin with? That’s going to be the next topic, in the second part of the book.