There is no step more uplifting, more momentous in the history of mind design, than the invention of language. When Homo sapiens became the beneficiary of this invention, the species stepped into a slingshot that has launched it far beyond all other earthly species in the power to look ahead and reflect.

– Daniel C. Dennett, 1996

It’s only sometime in the last 50,000 years that the archaeologists see the type of creativity that we associate with cave paintings, sewing needles, decorative carvings, pendants, and beads.  Most appear on the scene only during the last half of the last ice age – which would be the last minute of a two-hour-long “up from the apes” movie.

            The cave paintings speak, as Richard Leakey says, “of a mental world we readily recognize as our own.”  You can’t make such a statement for anytime earlier.  The Chauvet cave in France has fully representational paintings (even with perspective) dated to about 35,000 years ago, even earlier than that Cro-Magnon rock shelter.

            You may have noticed, however, that I have avoided talking about symbols.  That’s because I consider symbols an inadequate summary, not because I think the explanation “wrong.”  Here’s the OED on symbol:

2.  Something that stands for, represents, or denotes something else (not by exact resemblance, but by vague suggestion, or by some accidental or conventional relation); esp. a material object representing or taken to represent something immaterial or abstract, as a being, idea, quality, or condition; a representative or typical figure, sign, or token.

But at root, it’s an association between dissimilar things, much like Pavlov’s dog salivating for the bell in addition to dinner itself.  The important aspect for language purposes appears when the symbol stands in for something compounded of many other things, especially at a higher level of organization (more later) than mere objects and simple actions – say, the notion of a Rain God or an ecosystem.

            If one word has to suffice to summarize a broad collection of new abilities – perhaps a bad idea to start with –  I’d certainly pick a different word than the one popular throughout the twentieth century.  With notable exceptions (do read Terry Deacon’s The Symbolic Species), when people latch on to the idea of symbolic stuff, they stop thinking about the parts and pieces – and how they are coherently assembled at different levels of organization.  People go away thinking that they’ve achieved something by labeling all of it “symbolic” and may just argue in a circle.  Looking at the same material through the eyes of process, how neural circuits turn one thing into another, is more satisfying – and it enables you to spot more candidates for the big step up.

            That there is a stand-in is not what needs emphasis.  Human minds are indeed more capable of both broad categories and fine distinctions but what’s important here is that the referent is a complicated compound, often framed or structured.  Yet what I am calling “structured stuff” goes well beyond framing.  Structuring really makes long sentences fly, and likely complicated thoughts as well.

What else comes before structured language?  So far I’ve discussed some things that might be called protostructure:  staging intermediate products in food preparation and toolmaking, framing, and theory of mind.  I’ve mentioned imitation as an amplifier.  I mentioned protolanguage earlier, but let me now spell out what Derek Bickerton means by it.

            This unstructured language is what you see in toddlers, speakers of pidgins (the shared vocabulary between people who lack a common language, spoken without grammar), and in some stroke patients with aphasia.  It is often heavily augmented with gestures.  Most of all, the sentences are short in the manner of what two-year-olds produce – you can guess the meaning without any help from word order or inflections. This is the level of production that can be achieved in tutored bonobos like Kanzi and Panbinisha (they can do somewhat better at understanding than with production, much as I do with my rusty agrammatical German).  A lot can be inferred from context. 

       Long sentences, however, are simply too ambiguous without some mutually understood conventions about internal structuring into phrases and clauses.  A clause (it contains a verb) may be embedded in a phrase and vice versa.  The structuring conventions that help you figure out “who did what to whom” are called syntax and each dialect has a different way of doing things.  There are five other permutations of the subject-verb-object word order used in English declarative sentences, and all can be found in some language around the world.  Many languages convey structure with the aid of word endings that mark the role that the word is meant to play in that particular sentence; for example, –ly is an English ending that usually means that the word is going to modify a verb.

            “Universal grammar” is simply the tendency of all human groups to draw from a restricted set of structuring possibilities; not every structuring scheme appears to be possible, and that restriction likely says something about the limitations of the human brain.  For example, you can move one word out of place – say,  in making “What did she give to him?” out of the standard order “She gave what to him?” – but two things cannot be moved in the same sentence without making it hopelessly ambiguous.

The human faculty of language appears to be organized like the genetic code – hierarchical, generative, recursive, and virtually limitless with respect to its scope of expression….  Most current commentators agree that, although bees dance, birds sing, and chimpanzees grunt, these systems of communication differ qualitatively from human language.  In particular, animal communication systems lack the rich expressive and open-ended power of human language (based on humans’ capacity for recursion).

     – Marc Hauser, Noam Chomsky, Tecumseh Fitch, 2002

Syntax is the best-studied case of structured thought, one of the candidates for what “paid for” the rest, and certainly the earliest one to appear in modern childhood (kids pick one up between 18 and 36 months).  Once you have a syntax, you can convey complicated thoughts.  And the acquisition of syntax likely tunes up the brain to do other structured tasks.

            The step up to syntax is indeed a big one, as it involves such things as recursion.  In saying “I think I saw him leave to go home,” you are nesting four sentences like the Russian babushka dolls.   Structuring helps you discover the meaning of the sentence (the mental model in the speaker’s mind) but it isn’t the meaning itself.  Chomsky’s famous sentence to show the independence of syntax from semantics, “Colorless green ideas sleep furiously,” may not make any sense, but it doesn’t ring any structural alarm bells in our minds in the manner of “Colorless ideas furiously sleep green.”

            Syntax is not necessarily a tree, though people who like maps are quite attracted to the technique of diagramming a sentence using branch points with only two daughter branches.  At the heart of the structured sentence are clauses (easy to spot because each has a verb) and phrases.  It turns out that they can nest inside one another.  “John gave a present to Mary in the park last night” has only one verb but you can augment it by substituting “the present his sister bought” clause for “a present.”

            If you’re not a map person, you might like argument structure better.  This complementary way of looking at structure emphasizes the sentence as a little drama in which words play roles.  A noun might be the actor or the recipient – you have to figure it out from clues.  Some words, especially verbs, prompt you to find other words that go with them.  But not just any word. It has to be a word that can play the particular role.

            In any of its equivalents in the world’s languages, “give” is a verb with three roles to fill (there can also be associated nouns filling optional roles such as time and place, but give needs three nouns to fill its mandatory roles).  You need to find a noun that can play the role of the giver (“John”).  Another noun for the thing given (“a present”).  And a third noun that can play the recipient. Because an inanimate object (“present”) cannot be an actor, you can immediately eliminate one role possibility. 

            Try to speak a sentence without one of the three essential nouns and your listener will be perplexed and go in search of the missing word.  A missing subject probably means “you” as in the imperative form, “Give me that.”  But a billboard with a fragmentary sentence “Give him…” will cause a double take (exactly what the ad agency was trying to achieve) while you search for the pictorial equivalent of the object to be given.

            The so-called intransitive verbs such as sleep may not require much in the way of a supporting cast (“He slept.”), but you can always add optional phrases (“on the sofa” or “during the lecture”) or adverbs such as quietly or poorly.   Some languages such as Latin rely heavily on such “inflections”; word order may not matter very much.  In English, many inflections have disappeared in recent centuries; word order is often your main clue about what roles to assign, as in the subject-verb-object order of a simple declarative sentence.  But word order is only one clue to structure, not the main thing.

            The basic idea of argument structure, and of the lexicon in Chomsky’s more recent minimalist grammar, is that each word has some possible roles that form part of its mental baggage.  You simply know them from experience.  You can’t “break the blanket” because a blanket doesn’t have the right attributes to be breakable.  You can tear it or burn it or ruin it, but not break it.

            Presented with a sentence to analyze, you try to fit the pieces together in a way that makes sense.  Every required role must be filled, and no words should be left over once you have guessed the optional roles – your mental model of the sentence now hangs together.  With the meaning  thus extracted, you move on to the next sentence and its coherence-finding game.  If a sentence is incoherent, we ask for a repeat or just accept a reasonable candidate and move on.  If the sentence seems to have two perfectly reasonable alternative interpretations that leave us undecided, it may be humorous enough to make us laugh.

            The verb is usually the starting point of an analysis as it tells you how many obligatory roles must be satisfied by the other words of the sentence.  Some like “sleep” have only one role to fill, others such as “bring” and “give” have three; “bet” takes four as you also have to specify the condition of the bet.  So understanding a sentence with syntax is like solving a jigsaw puzzle.

            Language is all about taking a mental model of relationships in your mind – say, “who did what to whom” – and, via gestures or speech, getting someone else to guess exactly what you are thinking.  Language can get across a model of relationships even to someone who doesn’t share the context, even models of relationships that haven’t happened yet, even about abstract concepts like washing machines that eat socks.

            Language only needs to be good enough.  We often don’t need to finish sentences, because the rest can be guessed so easily.  We just need enough hints to allow us to guess correctly most of the time.  The task of language is to convey such relationships in an open-ended way, being able to convey novel amalgamations and have the listener effortlessly get the right idea.  If you are sticking to simple relationships, unstructured protolanguage may suffice.  But if you want to speak a long sentence, the ambiguity is a killer unless you can spot all of those prompts for frames and roles that we call grammar and syntax.

            Syntax is our best-studied case of structured thought, given how many ways there are to do the structuring job and how many schemes seem impossible, not used in any human language.  But syntax is not the only type of structured thought, and perhaps not even the first one to evolve.

Other structured aspects of thought are multistage planning, games with rules that constrain possible moves, chains of logic, structured music – and a fascination with discovering hidden order, with imagining how things hang together.  This structured suite likely enabled the giant step up to the modern mind of Homo sapiens sapiens.  Let me unpack what I mean by all the structured stuff.

Planning is not what a squirrel does as winter approaches.  Earlier I made that distinction in the context of physiological mechanisms.  Now note that from the evolutionary perspective, there is nothing novel about winter coming, even for a young squirrel.  It has happened every year to every squirrel for as long as there have been squirrels in the temperate zone, and said squirrel comes from an unbroken line of squirrels that survived winter’s dormancy of food resources.  Like mating, nest building, and nurturing behaviors, food hoarding is too important to be left to learning or innovation.  Planning pertains to novel situations, not learning or instinct.

     Note that instincts are another nice example of framing:  when a naïve animal is placed in an important setting for the first time, out pops an intricate never-experienced-before behavior like mating or nurturing.  “Context, context, context” is what those real-estate agents really mean by their mantra about the three most important considerations, “location, location, location.”

     Behaviorally modern humans plan for things that have never happened before, and in terms of choices.  ("Well, obviously if we go to the country this weekend, we can’t go to the baseball game Saturday night.")  Foresight often involves contingencies, another type of structure.  ("We can go to the country this weekend unless I have to work Saturday, in which case maybe we can go to a movie on Sunday.")  And by the time children reach school age, we start holding them responsible for having some foresight, and in a way that we do not apply to younger children or pets.  (In the immortal words of my mother, "Well, you should have thought about that before you did it!")

     It is useful to imagine a version of structured thought that is too slow for repartee.  It might be handy when you have time to think about things overnight, and so it can influence agendas and contingent planning – but even if you could speak a novel sentence aloud, no one might be able to interpret it without thinking about it overnight.  We usually assume spoken syntax comes first in evolution as it does in childhood, but overnight contemplation for planning  could have been an early payoff for structured thought, even before language.

Chains of logic, like those multistage novel plans, are considerably more difficult to handle than the simple forms of logic seen in other animals.

     Logical trains of inference allow us to connect remote causes through intermediate stages to present effects.  The basic element may be the primitive two-stage “after this therefore because of this” attribution, but reasoning in long chains is something at which we excel.  A supposed chain is, in reality, often a web instead, but the notion of being impelled down a path is very strong in us and it’s much more difficult for us to think about multiple causation.  Most of the things that happen in the world have multiple causes, of course, so we make a lot of errors of attribution.

     When not all the elements are clear, we have a propensity to guess at chains of causation.  This is very useful in doing science.  You can, of course, fool yourself very easily, which is why it is so important to keep track of what is provisional or pretense and what is well established.

Games have made-up rules that you have to consult before making your move.  Hopscotch and dance may have elements of play but they are also flexibly structured in ways that constrain choices.  But what I have in mind here is something with an arbitrary framework of allowed moves, against which possible moves must be checked before acting.

     Indeed, once four-year-olds have the ability to say “who did what to whom,” they love to keep track of the actions of others (and report deviations to the person in charge).  It becomes a game.

Narrative is closely related to framework-checking because we develop some standards for a good story – and not just epics but the everyday multifaceted stories, such as what we did for lunch.  There’s almost a “script” (with whom, where, what eaten, what discussed, and so forth).  If some part is missing, we often inquire.  So narrative is pattern on an even longer time scale than a sentence and it often has some blanks to fill in, just as in those “give him” sentences.

     I suspect that logical chains grow out of small-scale storytelling.  Someone pouring coffee into a cup provides a small story with familiar parts (called image schemas), the coffee pouring from one container, flowing along a path and then being contained by a second object.

     As Mark Turner points out in The Literary Mind, partitioning the world into object categories also involves partitioning the world into small stories: catching a ball, throwing it, sitting on a chair, drinking the coffee.  Many animals can do some of this, but modern humans can weave small stories into considerable narratives.  We use such chains to evaluate the wisdom of possible actions, to plan better ones, and when it all hangs together well enough to connect the underpinnings, we say that we have “understood” or “explained” things.

Music can be simply patterned as in rhythm and melody, and it can additionally be structured as in harmony.  Multivoiced music is what you get into with singing a fifth or an octave above someone else.  It is particularly impressive when one person can manage both, as when the left hand plays a different melody from the right hand.

     In western music, this is not much more than a thousand years old.  The counter melodies of the baroque, which Bach elaborated from church music that had already proved its emotional appeal in plainchant, are only a few centuries old.  The philosopher Karl Popper said that the development of multivoiced music was “possibly the most unprecedented, original, indeed miraculous achievement of our Western civilization, not excluding science.”

     Rhythm itself may be much older and the solo voice might be an outgrowth of ancient storytelling techniques, the melody (and alliteration and rhyme) used as an aid to memory about what comes next.  Music may elaborate social cohesion (marching music as a technique of the warmonger).  But there may also be individual advantages to be gained from showing off unusual abilities, not only musical abilities but virtuoso performances of other sorts (intricate dances, bower building, blindman’s buff).  When females choose males (rather than males excluding one another from access to females), genetic fitness tends to be judged by just such complex behavioral proxies.

Discovering hidden patterns is seen in music, jigsaw puzzles, and doing science.   We take great pleasure in “getting it.”  We love to see patterns emerging from seeming chaos, whether in doing a crossword puzzle or in doing science.  Coherence-finding is probably part of the source of our musical pleasure in listening to the left hand’s rhythm interacting with the right hand’s melody.

     As with those fill-in-the-blank test sentences, we’re always guessing about missing parts, trying to make wholes out of fragments.  Beyond-the-apes intelligence seems to be about making a guess that discovers some new underlying order – finding the solution to a problem or the logic in an argument, happening upon an appropriate analogy, creating a pleasing harmony or a witty reply, correctly predicting what’s likely to happen next.

     Indeed, you routinely guess what comes next, even subconsciously.  That’s why a joke’s punch line or a P.D.Q. Bach musical parody brings you up short – you were subconsciously predicting and were surprised by the unanticipated ending.

Note that music beyond rhythm, planning beyond the predictable seasons, and the logical chaining of ideas are all things that involve the novel, not just learned repetitions like singing the national anthem.  Novel structured stuff, with its search for coherence, is what we usually call “higher intellectual function.”

            The structuring that I have in mind for higher intellectual functions is not just a simple chain of events or intermediate products.  It is more like a symphony – and that reminds me of another important symphony that the brain had been producing for a million years before intellect.

I call them a “structured suite” because I suspect that they share a lot of the same neural machinery in the brain, one of the reasons why some functions might come (and go, in strokes or senility) as a package deal.  Perhaps the mental machinery for structuring is shared in part with some nonintellectual functions as well.

            Accurate throwing (not just flinging, which many chimps do, but practicing to hit smaller and smaller targets) is not usually a set piece like a dart throw or basketball free throw where the idea is to perform the action exactly the same way as your hard-earned standard.  Throwing at a prospect for dinner usually involves something novel: the target is not at the same distance or the same elevation as one of your standards; perhaps it is moving, too.  And throwing, much more than such ballistic motions as spitting, involves a structured plan.  Indeed, planning a throw has some nested stages, strongly reminiscent of syntax. 

            The highest velocity action is in the wrist movement, but planning it requires you to take account of what the elbow is doing:  wrist flicks, where mistakes matter most, are nested inside elbow uncocking.  What you want to achieve is a certain launch velocity, but you want the launch to occur at just the correct angle to the vertical.  That’s not a matter for the wrist alone.  You need to take into account what the elbow is doing – or rather, since this is advance planning, what the elbow plan is.  You have to estimate – guess, in other words – its motion.

            Elbow planning needs to know what the shoulder is doing.  And the shoulder too has a forward velocity due to what the whole trunk is doing, that forward velocity added by the legs.  So planning a throw is a nested problem, just like understanding “I think I saw him leave to go home.”

            You don’t do this as some assembly line during “get set,” marching from the fingers back up to shoulders, but you do have to juggle the finger, wrist, elbow, shoulder, and body plans, coordinating until you get the overall symphony right (as judged by your memories of similar-but-not-identical situations).  While there are a number of combinations that might suffice for a given target location, they have to hang together in just the right way or you’ll miss the target and go hungry.  You need, in other words, a coherent plan: all of the parts (and there are about a hundred muscles involved) have to form an internally compatible plan.  So, if the target is not standing at the location of one of your well-rehearsed set pieces, you need make a novel, staged, coherent plan.  And then execute it in an eighth of a second, getting all those muscles to come in at just the right time and with just the right strength.

            It was probably an expensive bit of Darwinian engineering, to get throws to be as good as what even eight-year-olds can accomplish on the playground of my neighborhood school.  Fortunately, once paid for by its usefulness in feeding the family with ever more frequent helpings of high calorie, nontoxic food, the neural machinery can perform other kinds of planning tasks as well, even for free.

Even without something for “free,” this sounds like heresy.  That’s because arguments about useful adaptations seem to assume (even when there is no need) that one cortical area is dedicated to one function.  As I mentioned earlier, you’d almost think that better throwing abilities ought to raise a bump on the head that could be labeled Hand-Arm Planning Center.  It would be separate, of course (another beginners’ error), from another bump labeled the Language Module.  There are two quick arguments that nicely serve to illuminate this understandable beginners’ mistake.

            One is that there may not be sufficient genetic variety to expand just one little region of the brain; the only variety available may be to increase major portions of the brain together – and that’s what most of the evolutionary data suggests.  “Increase one area, increase them all” may be the general rule.  There are important exceptions:  some lineages can increase the olfactory areas of the brain without  also increasing the cerebral cortex.  In general, raising a specialized bump is not an available option, however efficient it might seem as a first guess.  (As I’ll mention later, our intuitive notions of biological engineering often do not correspond to Darwinian reality, not any better than our intuitive physics matches up with Newtonian reality – and certainly not Einstein’s.)

            Second, though some of the best-understood regions of the brain such as primary visual cortex seem rather dedicated to a specialty, much of association cortex seems multifunctional.  Certainly there is much evidence suggesting that oral-facial movement planning can overlap with that for hand-arm – and with that for language, both sensory and motor aspects.  So we might even see “improve one function, improve some others in passing.”

Whatever economist said that “There is no such thing as a free lunch” obviously didn’t absorb the lessons from Darwin and his successors.  Pay via natural selection for one functionality like planning or language, and you may get the others such as music mostly “for free.”

            Let us assume that, however we got them, we have some brain circuits that are capable of running a process for making multistage coherent plans, and judging them for quality against your memory of what’s reasonable and safe.   Can you use them for other movement sequences as well as  hand-arm?

            Not only is there is a great deal of multiple use in evolution but you can see a nice concrete reminder on many a street corner – some missing concrete.  Wheelchair considerations paid for curb cuts but soon 99 percent of their use was for things that would never have paid their way – baby carriages, grocery carts, skateboards, wheeled suitcases, bicycles, and so on.  Maybe one of those secondary uses will eventually pay for further improvements but pay-before-using is not required.

            When did spare-time uses develop for the neural machinery for planning throws?  Hammering was likely the earliest, though I wouldn’t push cause-and-effect too far here.  With shared machinery, you can have coevolution with synergies:  better throwing might improve, in passing, the ability to hammer accurately.  And vice versa.  Though I am fond of accurate throwing as an early prime mover, remember that any of the uses of structured thought might improve the others, different ones at various times.  Even before the transition, language probably started paying its way.

            One of the free uses of the curb cut has already paid for a subsequent improvement.  I can remember when traffic jams occurred at the wheelchair ramps at airports.  The wheeled suitcases would queue up, awaiting their chance at the slot, and so in the newer airports, curb cuts were made as wide as the crosswalk.  When robotic developments enable both wheelchairs and suitcases to climb stairs, they’ll find curbs easy.  Indeed, the curb cuts may become obsolete for their original functions, though still frequented by bicycles and skateboards.  By the time that their original functions are forgotten, skateboarding will probably have evolved into a religion.  The skateboarders will surely claim the curb cuts as their ancestral sites of worship – and try to exclude pedestrians.

            In seeing the curb cut as created for its then-current best use, the skateboarders will be making the same inference that we make now when we posit that the evolution of the big brain is all about intelligence.  Maybe.  Maybe not.

            Secondary use initially gets a free ride, and it doesn’t necessarily retire the original use in the manner of Darwin’s example, the fish’s swim bladder that turns, after an intermediate period of dual use, into a lung.  (That’s where Darwin also cautions about going overboard on adaptations via natural selection, observing that conversions of function can also be quite important.)

            But just because some secondary use is possible doesn’t mean it instantly happens.  We were likely capable of structured music (what you’re doing when the left hand plays a different tune from the right hand) just after the big transition, long before Western music got around to using it about a thousand years ago.  Just because novel symphonies of hand-arm movement commands had been getting better and better for a million years doesn’t mean that secondary use for spoken language had to happen, or say when.

So when do kids pick up structured stuff from their experiences in life?  Modern children can do it from speech between 18 and 36 months of age, even before they can tie their shoes (fine movement control matures more slowly) – provided, of course, that their culture provides them with lots of examples of structured stuff to puzzle over.

            Let us say that, back 150,000 years ago, it was only when practicing accurate throwing at age eight that a lot of novel structured stuff was experienced.  Protolanguage was perhaps around, but short sentences can be understood without looking for structural hints as to roles.  All of that practice throwing at novel targets served, let us say, to softwire the brain in the manner of learning, so that adult performance was better on structured stuff.

            But picking up structured stuff also depends on an individual’s acquisitiveness, as in those modern kids picking up many new words a day.  Some kids are acquisitive of structured stuff earlier than others; it’s probably some bell-shaped curve.  And their performance as adults on structured stuff depends strongly (if we are to judge from the deaf kids without sign language environments) on a window of opportunity (to be dramatic, let us say it opens at age two and flattens at five years of age, that thick line).

            So being precocious pays off as an adult, because you do a better job of softwiring for structured stuff, having done it earlier than the average child.  There are three cases to consider:

·         The age when interested doesn’t really overlap with the window of above-average softwiring opportunity.  So the more precocious kids (left side of the top bell curve) aren’t better as adults than the average kids, no matter when culture exposes them to structured stuff.

·         The precocious kids are overlapping with the sensitive period for softwiring the brain for structured stuff – that earlier-is-better segment of the thick line – but culture doesn’t provide any structured examples that early, so they never tune up when earlier is better.  (The tragedy of the modern deaf kids with hearing parents, but also what anatomically moderns might have been like before syntax.)

·         Culture provides early examples of structured stuff via, say, speech.  Now earlier is better for eventual adult performance.  And those successful adults are providing the next round of variations centered on their (skewed) average via Darwin’s inheritance principle.  So the more precocious of the offspring of the previously precocious are even better as adults.  With this, successive generations can keep marching to the left, back up the earlier-is-better part of the thick line.

This is just another aspect of what are called epigenetic factors in development, where the environment serves to trigger an alternative path in development.  In the case of plants, it is sunlight that provides a cue to a new branch as to whether to grow upward and sprout leaves or to grow downward and develop root hairs. Culture too can provide important cues for making development choices and directional selection can move the succeeding generations up the curve.  Evolution interacts with development via the environment (the research area is known as EvoDevo) and that’s why nature-nurture and genes-culture are such false dichotomies.

            For now, note that none of this requires very much of what is usually posited by the archaeologists: some new genes to initiate the transition.  Even the tweaks in acquisitiveness might come later, if the curves originally overlapped the window of better softwiring opportunity.  In just one generation of kids finally being exposed to structured stuff at earlier ages, the next generation of adults would be far more capable, thanks to softwiring in youth.  (In fact, it need not wait until the next generation:  older children are usually the frequent companions of younger children, and so a mother speaking structured sentences can infect her children, who themselves infect other children a few years later.)

      So the simplest version of a rapid ascent to structured thought looks like this:

·         PRE:  Structured stuff is learned in later childhood with accurate throwing and toolmaking.

·         TRANSITION:  Some older children and adults manage to slowly add structure to protolanguage utterances.

·         POST: Young children are now exposed to structured stuff via the speech of caregivers, even before they can “tie their shoes,” and they then softwire their brains to really fly as adults.  But because structured stuff via one route may carry over to such things as planning and logic, most of the structured suite pops into place in a few generations.

So the archaeologist’s summary of what “behaviorally modern” involves – abstract thought, planning in depth, innovation, symbols, storytelling – overlaps with higher intellectual function.  But a “symbolic” formulation doesn’t hint at the underlying unity that I’ve been covering here.

            My point is that much of this behavioral modernity is structured – syntax, contingent plans, music, logical chains, narratives, games with rules, house-of-cards analogies – and that we compulsively guess to fill in missing pieces in the inferred structure.  Guessing at structured stuff means we can make a lot of mistakes, so we have to be constantly concerned with quality.

            Quality and coherence are also what limits creativity.  I will devote an entire chapter to creativity after saying something about how much of higher intellectual function seems half-baked, what you ordinarily see in a prototype rather than a finished, well-engineered product.  Perfection you don’t get, not from Darwinian evolution.  And the quality controls are spotty.  But culture – especially education and medicine – can sometimes patch things up, if society works hard enough at it.