I am interested in language and its evolution. Recently, I read a book related with a story of our language. I don’t know you but I am not so good at recalling things from books. So, I start taking notes while reading. In this post, I’d like to share these notes about “The Recursive Mind: The Origins of Human Language, Thought, and Civilization”. Before sharing the notes, there are two caveats I’d like to point out: (1) These notes may not be very useful for others. My intention was that notes would have merely been for my personal usage. That’s why some notes might give a feeling that they are dangling in the air. That is, they might not be self-explanatory. I try my best to reduce happening of those situations but there is a trade-off between creating something for personal use (less context, less time) versus for public use (more context, more time). (2) Reading these notes doesn’t mean that you don’t read the book anymore. It’s actually quite opposite. It’s an appetizer (yes, a very long one) for a main dish.

Details for the book: The Recursive Mind - The Origins of Human Language, Thought, and Civilization by Michael C. Corballis

Let’s get started.

Part I: Language

  • Hippocampus provides mental time travel: imagining past and future. Destruction of hippocampus makes the victim stuck in the present.
  • Recursion in language: “Jane, who flies airplanes, loves John.”. We comes up and parse recursive structures in speech.
  • Pinker and Jackendoff: “The only reason language needs to be recursive is because its function is to express recursive thoughts. If there were no recursive thoughts, the means of expression would not need recursion either.”. However, author argues that there are nonrecursive languages that express recursive thought. The Pirahã, a remote Brazilian tribe, has nonrecursive language.
  • Pinker: Recursion has dual definition: as a process and a structure.
  • Minimalist Program - Noam Chomsky’s most recent theorem: Human thought is generated by a merge operation, applied recursively.
    • I-Language (internal) - Thought language. Common for all human beings.
    • E-Langauge (external) - language that actually spoken and signed.
  • Some scientist think that human brain is like Swiss-Army Knife. It’s called Swiss-Army Knife Model of the mind - a blade for each purpose.
  • Author says that this book aims to suggest that there are deeper aspects of human thought and the recursion is one of those principles — and perhaps the most important one.
    • Also author does not completely embrace the modular view (Swiss-Army Knife Model) assumed by evolutionary psychologists. However, he agrees that a distinctively human mind evolved during the Pleistocene, 2.6 M years ago to some 12K years.
  • “Working memory” - linking non-sequential parts of the sentence
    • My dog, who eats bananas, often gets sick.
      • My dog (remember this part) —> often gets sick.
  • Center-embedded recursion.
    • the most demanding recursion
    • Even humans are not good at parsing more than 3.
  • Chomsky’s view of language:
    • Chomsky seeks deeper rules that would apply to all languages. These rules are known as universal grammar.
    • Merge operation can be seen I-Language but not E-Language (The Pirahã, the Brazilian tribe)
      • Pirahã has little sense of time, no fiction and no myths, no sense of history.
      • They have thoughts involving recursion but use non-recursive language to express them.
      • Pirahã baby raised in Boston have no problem to learn Bostonian English.
    • Also, Chomsky’s I-language has no external reference, and basis of all languages, therefore cannot be evolved through natural selection. Thus, Chomsky thinks that it must have emerged in a single step, perhaps a mutation, probably within the past 100,000 years. He calls that individual as Prometheus.
      • Another way of saying this: I-Language: language of thought. And it has no external referents, and it’s precede to evaluation of E-languages, the language that we actually speak and sign — it cannot have arisen through natural selection (has no advantages in the terms of natural selection). Because there is no way to output I-Language before E-language. So, natural selection doesn’t work for that. It should be a singular event in a single individual.
      • Question: I do not agree Chomsky’s view but what if I-Language provides a new way of thinking to Prometheus; kind of thinking that makes Prometheus superior to other humans? Perhaps I-language does not show itself as E-Language however this new thinking enabled by I-Language may create some advantages in the terms of natural selection. How do people who do not believe Chomsky’s view dispute this? How can they be sure that I-Language has no external referents? Also, what does Chomsky think about the argument that I-Language has no external referent, thus no advantages in natural selection process?)
    • From a Darwinian perspective this view is deeply implausible. Language is complex. Complex biological structures can be expressed by the power of natural selection.
    • Language was/is also as a kind of passport.
      • Nicholas Evans suggests that the diversity of language was not driven by geographic isolation, since they coexist in areas where there are no geographic barriers, and several different languages are often spoken within the same household. Language variation also seems to be driven by more than random drift. Evans suggests that language serves as a kind of passport, marking the right to belong to a particular local society. As groups split off, they may make deliberate moves to differentiate their languages. For example, in the Uisia dialect of the Buin language on Bougainville Island the gender agreements have all been reversed relative to those in the other dialects. All the masculine words have become feminine and all the feminine words masculine. This seems clearly a deliberate move to differentiate a particular subcommunity from the rest.
    • Question for Chomsky’s view: Is the degree of diversity recorded by researcher could have arisen in so short a time? That’s why author thinks that grammar itself evolved gradually rather than as a singular event withing the past 100K years.
  • Grammaticalization
    • If grammar does not depend on some inborn, universal set of principles, what does it depend on? It seems it’s more a gradual process, driven by practical concerns rather than biological predisposition.
    • One of the processes involved in grammaticalization has to do with the changing roles of words, leading to more efficient and economical expression. Functional words emerged from content words.
    • Breaking down concepts into component parts — changing holistic signs to more combinatorial format.
    • Even words may gained combinatorial structures over time.
      • phonomes - morphomes
      • “Today’s morphology is yesterday’s syntax.”
        • he laugh did —> he laughed.
        • -ed comes from did
    • Author’s claim: Language is not a product of universal grammar that suddenly emerged in some comparatively recent individual called Prometheus. It comes about gradually as a product of culture and accumulated experience and a practical concern to make communication more efficient.
    • Any universal principles underlying language can be regarded as principles of human thought and not specific to language. Even recursion appears not to be universal. It might be suggested that recursion is merely part of a toolkit for constructing language, and that not all languages use all of the tools.
  • Speech might evolved from singing. This idea explored by Steven Mithen’s book named The Singing Neanderthals.
  • Animals are different than us because their vocalization is emotional rather than voluntary control like human laugh
    • Even they have little or no ability to produce anything resembling human speech, animals may have surprising ability to understand.
    • Learning by exclusion — the dog doesn’t know one item among known items. It can still retrieve it by excluding it from known items. The ability to apply a label on a single trial is known as “fast mapping” and has hitherto been thought to be restricted to humans.
    • break sentences down into words — it was considered as a unique ability for humans.
  • Animals are better in manual gestures than vocalization. Manual gestures are used more freely and flexibly than are vocalization, and it’s intentional rather than emotional like vocalization.
  • No evidence for recursive parsing of sequences in nonhuman species. In language, at least, recursion may indeed be uniquely human, as Chomsky and others have maintained.
  • Author argues that human language wouldn’t have been possible were it not for the recursive nature of human thought.
  • Another evidence for the language evolved from manual gestures is that teaching through gesture and use of keyboards, apes to speak has much greater successes than through vocalization.
  • Mirror Neurons (“Monkey see, Monkey” do neurons)
    • Gestural theory received a powerful boost after the remarkable discovery of so-called mirror neurons in the primate brain.
    • Monkey experiment: The same neurons are active when not only the monkey does some action, but also when monkey sees another monkey does that action. This area is a part of the frontal cortex of F5.
    • Homologous area to F5 in human is Broca’s area - involved not only in speech but also motor functions unrelated to speech, such as complex hand movements, sensorimotor learning and integration, which explains why langauge can be either vocal (speech), or manual (signed languages)
    • Besides Broca’s area, another well-known language area is Wernicke’s area (not that language more widely distributed than these two areas).
    • These overlap has led that language get out of the mirror system itself.
    • So, mirror system in monkey is in essence a system for understanding action. Monkey understands action of others in terms of how it would itself perform those action. This is called “motor theory of speech perception”, which holds that we perceive speech not in terms of the acoustic patterns it creates, but in terms of how we ourselves would articulate it. Very interesting.
      • “This theory arose from the work the Alvin Liberman and others at the Haskins Laboratories in the United States, who sought the acoustic principles underlying the basic units of sound that make up our speech. For example, b sounds in words like battle, bottle, beer, bug, rabbit, Beelzebub, or flibbertigibbet probably sound much the same to you, but the actual acoustic streams created by these b sounds varies widely, to the point that they actually have virtually nothing in common. The same is true of other speech sounds, especially the plosive sounds d, g, p, t, and k; the acoustic signals vary widely depending on the contexts in which they are embedded.” So that’s why when we hear each sound as the same in each case because we hear it in terms of how we produce it.
    • Another important suggestion enabled by the exploration of mirror neurons: As we saw, vocalization in monkeys (and animals except humans) are unintentional and impervious to learning however, mirror system covers intentional action and it’s clearly modifiable by experience (e.g., monkey brain can respond sounds of certain actions such as cracking the nuts; those actions can only have been learned). These mirror neurons are not activated when monkey calls. This suggests that mirror system is separated by vocalization system, and our forebears, the mirror system was already set up for processing sounds caused by manual activity but not for processing of vocal sounds.
    • Motor theory of speech perception reminded me the embodied-simulation hypothesis. Couple of years ago, I read a book related with this: Louder than Words.
  • Bipedal hominins have free hands and it helps further development for expressive manual communication. Movement of arms and hands can mimic the movement of objects through space and facial expressions can convey emotions of events being described.
  • Signed language evolved to be less iconic (e.g., sign for play piano mimics the action) and more arbitrary, in the interests of speed, efficiency and grammatical constraints — this process is known as “conventionalization”.

The switch from manual gestures to speech

  • The first part of the switch was probably the increasing involvement of the face (facial expressions). Experiment was this: people who open their mouth bigger when they have bigger objects (not food) in their hands. However, even the object is not food, the connection might depend on our eating habit. I don’t really like this experiment (at page 67 for more detail of the experiment).
  • The final act was the incorporation of vocalization. Part of the reason for this may have been facial gestures increasingly involved movements of the tongue that are invisible. Speech itself can be viewed as gestural rather than acoustic (see above). The motor theory of speech perception is based on the idea that perceiving speech sounds depends on the mapping of those sounds on to the articulatory gestures that produce them (called articulatory phonology), in which speech is understood as gestures produced by some articulatory organs (lips, the velum, the larynx, the blade, body and root of the tongue). So, if the speech is understood as gestures (not acoustic signals), incorporation of vocal gestures into the mirror system may have been relatively small step for mankind. Now, I am curious about the activities that musical instruments cause to the animals. My guess is that the music is a manual activity (not like speech) and the mirror system in monkey’s brain would be active to process these sounds.
  • Why the switch, then? Sign language can give extra clues about the meaning than speech can do, thanks to 3d medium ofrsign language. So, advantages of speech over manual language are likely to be practical rather than linguistic.
    • Spatial reach - speech is more accessible. also manual gestures requires light. No artificial lighting back in time. It would be really hard to communicate by sign language. The Sans people (modern African hunter-gatherer society who depends highly manual gestures) frequently said when a disagreement happens: “We will go to the fire so that we can see what they say”
    • Speech is energy efficient.
    • It creates diversity and language fortress in small people groups.
      • Language diversity makes intruders and freeloaders hard to penetrate the culture. Speech which is much more diverse than sign language, makes the culture impenetrable to intruders.
      • 1500 possible speech sounds but no language uses more than 10%. Child has a distinct ability to discriminate different sounds but when she/he trains itself only set of sounds, child loses ability to “hear” other sounds. Japanese people have difficulty to distinguish R / L sound, for instance.
    • Speech frees the hands.
      • Increases the efficiency of pedagogy - you can teach someone explaining and demonstrating the action simultaneously (think about cooking shows in TV).

Part II: Mental Time Travel

  • No difficulty for humans to mentally travel other places and other times.
  • Language may therefore evolved primarily to enable us to share our stories, our memories, plans and create a common culture.
  • Episodic memory: memory that its job is to remember the actual events located in time and space. “I remember my first fight in the park close to our house.”
  • Semantic memory: I know that Ankara is the capital city of Turkey. I don’t know when/where I learn this fact but this is a knowledge.
  • paramnesia: false memories.
  • Without human contact, the language won’t be developed (A sad story about it: (1) Genie case, and (2) Guardian article about Genie)
  • Implicit memory
    • classical conditional learning (e.g. Pavlov experiment, The Little Albert Experiment), involuntary
    • operant conditioning - voluntary, dinner bell serves a signal you to go to the table.
    • do not involve consciousness - one can remember the experience of learning to ride a bicycle but this is different than learning itself.
  • Explicit memory
    • (1) Episodic and (2) semantic memory.
    • Episodic memory:
      • Episodic memory is not a video on Youtube consisted of sequences and can be distorted or embellished. It helps us to shape the future.
      • Episodic memory captures the approximate time of the event that provides an general understanding of time itself.
      • Allows us to do mental time travel; to remember past events as well as to imagine the future events. This enables us to fine-tune our lives. “episodic future thinking”
      • The importance of episodic memory is nothing about remembering the past. Therefore, episodic memory does not show an amazing performance to remember things (We don’t remember the most of the details about event or we sometimes mixed events that didn’t happen. Famous experiment related with this: When you tell a person a large set of words related with each other (i.e, kitchen utensils) and ask whether he/she did hear the word not in the list. You’ll get poor performance), but rather its role in constructing future scenarios and fine-tune our life. Ulric Neisser says: “Remembering is not like playing back a tape or looking at a picture; it is more like telling a story.”.

Is Mental Time travel unique to humans?

  • Author claims that mental time travel is unique to human even there are experiments showed that animals have mechanism resembles to this. However, author argues that these experiments didn’t show animals go back to past and remember these. This might be because birds (very successful animals in this regard) have useby-date (when versus how-long ago) not necessarily comes from mental time travel. Also designing an experiment to test an animal does a mental time travel is fundamentally hard. Bird can’t say that ‘hey I vividly remember the moment I hided a peanut here yesterday’.
  • www memory: storage of what where and when.
  • Note that birds are better than great-apes in this regard. Also they are better tool makers.
  • Bischof-Köhler hypothesis: It states that only humans can flexibly anticipate their own future mental states of need and act in the present to satisfy them.
  • In some point at the end of the Chapter 6, author says this: “It is perhaps through iteration rather than true recursion that we understand the nature of time. Just as tomorrows extend indefinitely into the future, so yesterdays extend indefinitely back into the past.”. How come we reach this conclusion, I don’t really know.

Grammatical language

  • Author thinks that the grammatical language evolves primarily to enable human to share episodes. This would also provide future planning and cultural expectations. Language helps us to share knowledge as well but author’s main claim is to enable us to communicate about events that do not take place in here and now (unlike animals which are always living in “now and here”).
  • The first requirement for grammar is that symbols for not-physically-present things.
  • Symbols derives from practical concerns rather than linguistic necessity.
    • Zipf’s law applies this phenomenon actually: Length of the word is inversely proportional to its rank in frequency.
  • We’re “the symbolic species”. — Terrence Deacon
  • Language reflects thought, rather than vice versa. Also I think thoughts are highly dependent to environment. It’s possible to say environment —> thoughts —> language.
  • Language is generative. We can construct and understand sentences that we never heard.
  • We know through Noam Chomsky that language cannot be explained in terms of learned sequences. Instead, it depends on rules which combine words in precise ways to enable us to extract meaning.
  • Mental time travel is also a recursive function.

Part III - Theory of Mind

  • Ability to understand what is happening in the other’s mind is known as theory of mind.
  • Emotion is simplest mental state to read.
  • Some test to investigate theory of mind for kids:
    • Three Mountains test.
    • Sally-Anne Test: test children’s ability to infer false beliefs. A recent study suggests that babies actually understand false belief by the age of two.
  • Theory of mind evolved because we live complex social lives which demands cooperation and social skills.
  • It’s recursive: “Ted suspects that Alice believes that he does indeed suspect that Fred thinks that she wants him (Fred) to go away”. We cannot only infer what she thinks but also infer that she infers what I am thinking.
  • Temple Grandin, documentary about her and her high functioning autism (as known as Asperger’s syndrome): The woman who thinks like a cow. Short documentary and it’s Interesting to watch. Recommended.
  • Imprinting: chromosomes come in pairs (one from the mother and one from the father), and imprinting means that one or the other is dominant. Maternal genes are expressed most strongly in the cortex — which is the place for theory of mind, language, social competence, whereas paternal genes tend to be expressed in the limbic system, which deals resource-demanding basic drives - aggression, appetites, and emotion.
  • Autism can be regarded as the extreme expression of paternal genes, schizophrenia is as the extreme expression of maternal genes.
  • Correlation between imprinting and biological sex
    • Males leaning toward the autistic end
    • Females toward the schizophrenic end
  • Imprinting may have played a major role in human evolution, one suggestion is that evolution of the human brain was driven by the progressive influence of maternal genes, leading to expansion of neocortex and the emergence of recursive cognition such as language and theory of mind.
  • Is Theory of mind special for humans?
    • Animals have it In a very limited way. Not a complex abilities.
    • No self-awareness except chimpanzees and some other animals such as dolphin and elephant.
      • Even some of these animals above can pass the test, this doesn’t imply more than a physical stance; an animal may recognize itself as a physical object, without any necessary understanding that this physical object has desires, beliefs, emotions or dreams.
  • Author says that grammatical language depends on:
    • mental time travel
    • adaptive advantage of being able to share episodes
    • theory of mind
  • Disambiguation of Implicatures:
    • Sperber and Wilson suggest that there are submodules that help narrow down the alternative meanings so reduce the computational demand of tracking each and every meaning path. For instance we have built-in attention sensitivity (we understand and focus other’s attentions).
    • We continually maximize the relevance of available inputs.
    • This is so-called relevance theory which suggests our minds tune moment by moment to what is most relevant, and reduce the linguistic demand. Language is as a meeting of minds.
  • Gestural Origins
    • Author argues that the origin of language lie in manual gestures, the language-like behavior in non-human species is gestural.
    • Non-human species are essentially imperative, designed to bring reward or advantage to the gesturer. However, human has declarative function. For instance, a toddler in the bus, which is his first ride, catches people’s eyes, and points out cars, buses outside, sharing his excitement with the people.

Part IV: Human Evolution

  • The most critical period is considered the Pleistocene (Ice Age), dating from some 2.6 millions years ago until around 12,000 years ago, thinking that this was the epoch during which the human mind took shape.
  • Descartes: mind-body dualism. Serious criticism comes from Darwin’s theory of evolution by natural selection, which says that there is no fundamental difference between humans and other species.
    • Theodosius Dobzhansky: “Nothing in biology makes sense except in the light of evolution”
  • Recursion might be observed in several other properties previously claimed as unique to humans:
    • language
    • episodic memory
    • mental time travel
    • theory of mind
  • Humans can go beyond first-order intentionality to perhaps as high as fifth or sixth order.

Chapter 11: Becoming Human

  • 20 hominin species have been identified from fossil remains, but only one species of hominin remains; guess who.
  • Bipedalism
    • Humans are not evolved from knuckle-walkers: We’re not similar in this with chimpanzee and gorilla.
    • It’s still unclear just why bipedalism was retained.
      • Locomotion is not the reason of bipedalism. Contrary, an average chimpanzee can reach speeds of up to 48 km per hour (even faster than a top athlete runs at about 30 km/h)
      • Bipedalism has a lot disadvantages: neck and back problems, hemorrhoids, hernias, excessive pain of giving birth. But there must be adaptive advantages: freeing the hands and arms and perhaps leading eventually to manufacture. However, manufacture emerged very late so it shouldn’t be the reason of bipedalism. Freeing hands would have been adaptive for other purposes, though, such as grooming, carrying things, and fighting.
      • Throwing
        • One possibility is standing up allowed us to throw things which creates superior defensive and hunting skills. Charles Darwin suggested this when he wrote: “In throwing a stone or spear a man (sic) must stand firmly on his feet.”.
          • In The Throwing Madonna, William H. Calvin suggested that it was women who were the throwing experts.
        • Right arm is largely controlled by the left brain. Accurate throwing needs precise timing. Bipedalism —> throwing —> programs left brain for timing might be favorable for evolution of speech, which also requires precise timing.
        • Accurate thrower is important for protecting the human group and hunting the prey.
          • It’s not only a matter of survival against threat. Sexual selection might also played a role.
            • Players from baseball, cricket, rugby, football, discus, javelin are very attractive for women.
          • Throwing seems like not the whole story but for powerful throwing requires flexibility of the wrist would have hindered the use of the hands for locomotion.
          • Throwing also explains the seeming perfection of the human hand — As Jacob Bronowski says “the cutting edge of the mind” for hands.
        • Hands have evolved to provide two kinds of grip. A precision grip (for throwing things) and a power grip (clubbing things).
      • Social Bonding
        • Sarah Blaffer Hrdy suggested that social bonding evolved first in the context of child rearing. Great apes are loathe to allow others to touch their infants during the first few months, whereas human mothers are very trusting in allowing other to touch, carry, nurture their babies.
        • The exposure of infants to variety of others would also foster theory of mind, teaching infants to gauge the intentions of others, learn whom to trust. Hrdy argues that this bounding may even have established the initial conditions of favoring of increase in brain size, social learning, teaching, and language itself.
        • The real challenge for humans in history was not climate, weather, food shortages, or predators. The real challenge is human itself. Humans have proven as adept at killing each other as at killing non-human predators. For successful adaption, humans needs to predict other’s mind if they want to collaborate or compete. Our lives depend on a subtle calculus of “sharing” and “greed”. Author says: “left-wing socialism versus right-wing individualism, if you like”.
  • Cooked food is softer, leading to the small mouths, weak jaws, and short digestive system. This distinguished Homo from earlier hominins and other apes.
  • Brain size
    • Positive selection
      • Abnormal spindle-like microcephaly associated (ASPM) gene, evidence suggests strong positive selection of this gene in the linage leading to Homo Sapiens. This gene known to be a specific regulator of brain size.
        • Selective sweep appears to have occurred as recently as 5,800 years ago: Human brain is still undergoing rapid evolution.
      • Microcephalin (MCPH6)
    • Negative selection
      • One gene that encodes enzyme that produces an acid that inhibits brain growth. It was once active genes that were inactivated.
      • This gene is absent in Neandertal fossils (developed brain) and present in other primates.
      • Other gene that encodes the myosin-heavy chain (MYH16) responsible for the strong chewing muscles.
        • Chimpanzees, gorillas and early hominins have it.
        • It’s deactivated an estimated 2.4 million years ago for humans.
        • Speculation that the shrinkage of jaw muscles and their supporting bone structure were removed which were a further constraints on brain growth. This may have signaled a change of diet from tough vegetables to tender meat or it may had to do with the increasing use of the hands rather than jaws to prepare food.
  • Migrations
    • Instead of traveling back and forth between different locations, hominins migrated one place and then move on rather than returning.
    • Homo erectus - mostly Asia. Nearly equivalent species known as Homo ergaster stayed in Africa.
  • Tools
    • Author’s guess is that recursive thought probably evolved in social interaction and communication before it was evident in the material creations of our forebears.
  • Human, at last
    • “It is generally reckoned that the species Homo sapiens who emerged some 170,000 years ago was “anatomically modern” human at last. This was a large-brained species equipped with the intelligence and social understanding of modern humans. If you were to snatch an infant from that time, and raise that infant in the present-day world, he or she would probably adapt as well as any modern-born person to the exigencies of modern life, whether as stockbroker, ballerina, modern-day hunter-gatherer, university professor, or used-car salesperson. The Pleistocene had gradually shaped recursive modes of thought that allowed complex theory of mind and mental time travel, and allowed for the relaying of memories, plans, and stories for the betterment of both the society and the individual.”

Chapter 12: Becoming Modern

  • Mitochondrial DNA (mtDNA), a form of DNA that is passed down the generations from mother to daughter. In contrast with DNA, it is not involved in the processes of recombination that occur in eukaryotic reproduction. Changes in mtDNA arise only through mutation, allowing us to trace ancestry through females.
  • Author argued that language evolved first as a system of manual gestures, shifting gradually through facial gestures to articulate speech.

Final Thoughts

  • Author thinks that recursion as an extension of existing faculties is a key element for uniquely human features as language, theory of mind, and mental time travel. Different animals have different faculties similar to human but they don’t have this recursive characteristic that makes us unique.
  • Author emphasizes that even recursion is critical to the evolution of human mind, it’s not a module.
  • It doesn’t depend on some specific mutation, or special kind of neuron, or the sudden appearance of a new brain structure. Instead of those, he argues that recursion probably evolved through progressive increases in short-term memory and capacity for hierarchical organizations — those things probably dependent on brain size, which increased incrementally, albeit rapidly, during the Pleistocene (According to Wikipedia: Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago.). I like to think about this part, and quoted from the author: “But incremental changes can lead to sudden more substantial jumps, as when water boils or a balloon pops. In mathematics, such sudden shifts are known as catastrophes, so we may perhaps conclude that emergence of the human mind was catastrophic.”
  • Language is a human universal and he suspects that theory of mind and mental time travel are the same, too.
  • Language that adapted to thought, rather than thought that was shaped by language.
  • There is no reason to suppose that the recursive mind evolved in a single, magical step (like Chomsky proposed on Prometheus); instead, it was shaped by natural selection, probably mostly during the last two million years.