William H. Calvin, "The Mind’s Big Bang." An after-dinner speech in San Diego (5 August 2000).  See also

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This 'tree' is really a pyramidal neuron of cerebral cortex.  The axon exiting at bottom goes long distances, eventually splitting up into 10,000 small branchlets to make synapses with other brain cells.
William H. Calvin

University of Washington
Seattle WA 98195-1800 USA

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The Mind’s Big Bang

        William H. Calvin  

The upper Paleolithic art and tools speak, it says here, “of a mental world we readily recognize as our own,” to quote Richard Leakey - who, for the last year, in one of the strangest power-sharing arrangements ever seen, has been the number two man in the government of Kenya, with powers perhaps greater than those of Al Gore.  He was elected to that position, as best as I can tell, by the World Bank, as a condition for resuming financial aid to the corrupt Kenyan government, which they did this last week after a three-year hiatus.  I remember how impressed I was in 1976 when Don Kennedy gave up the fun of doing neurobiology in order to become the Commissioner of the FDA, and then president of Stanford, and now editor of Science.  For Richard Leakey to give up doing paleoanthropology to try to rescue his country from a corrupt tribal coalition seems even more magnanimous, if anything.  But let me now turn to a simpler time, the one Richard Leakey was speaking of, the far-simpler times before it, and why things took a big step up in complexity about 40,000 years ago.

            Complex toolmaking bursts on the scene rather suddenly between 50,000 and 35,000 years ago, compared to the infrequent progress in toolmaking since the common ancestor with the chimpanzees about 5 million years ago.  And it occurs about when cave art makes us aware that something symbolic might also be happening (see the pictures in the July 2000 National Geographic).  As Ian Tattersall says, “This… stands in dramatic contrast to the relative monotony of human evolution throughout the five million years that preceded it.  For prior to the Cro-Magnons, innovation was… sporadic at best.”

            This has been a big puzzle in human evolution, obvious a half-century ago, and it has only become more puzzling as they’ve gotten more sites and more dates.  Most of you already know about it because of the tendency of paleoanthropologists to speak of anatomically-modern Homo sapiens starting perhaps 150,000 years ago and, separately, starting about 40,000 years ago, of behaviorally-modern Homo sapiens.

            So did a new species appear then?  Not by the usual criterion, based on fossil evidence.  By 150,000 years ago, there were people that looked like us.  They likely had modern brain size but, judging from their art and technology, they didn’t think like us.  The British anthropologist Kenneth Oakley suggested in 1951 that the art-and-tools efflorescence of the Upper Paleolithic might have been when fully modern language appeared on the scene.

            Before then, did anatomically-modern humans just talk silently to themselves, like the animals in Gary Larson cartoons?  Most people assume they did.  They believe that our pet cats and dogs think, and certainly apes.  So let me tell you what I always say to such statements about the great apes:  If they could talk to themselves with the complexity we seem to assume, they could think complex thoughts.  And if they could think complex thoughts, they’d be able to plan ahead and do other things clearly advantageous to themselves.  We’d see the evidence for complex thought in their behavior, even if they didn’t talk about it.  Indeed talking like a 2-year-old wouldn’t imply complex thought, so the issue really isn’t speech per se.

            And after you’ve learned enough animal behavior to also know what they don’t do, you begin to wonder.  If chimps had complex thought, for example, they’d be the terror of Africa.  Instead of their ganglike hit-and-run raids on their neighbors, chimps would make war on their neighbors using stockpiling of supplies and staged, coordinated attacks.  We do not see that.  No one sees much evidence of logical planning in the chimps, not the kind of planning where two or three novel stages need to be worked out in advance of acting.  No such evidence in chimps, and certainly not in Gary Larson’s talking fruit flies.

            Yes, it is easy to miss evidence.  As the archaeologists say, absence of evidence is not evidence of absence.  But since the great apes don’t much plan for tomorrow, I’m willing for the moment to consider that complexity of thought may not be present in them.  And maybe this same viewpoint ought to be applied to our ancestors, too, at least considering the possibility that complex thought is not much older than the evidence that Tattersall and Leakey are talking about, at 40,000 years ago.

            This efflorescence of technique is what is sometimes called “The mind’s big bang.”  I will first review what is meant by complex thought, especially structuring of thought and extended consciousness.  Then, I will ask two questions:  1) What was thought like back in “antebellum” days?  2) What brain mechanisms might kick in, to produce the efflorescence?  This will lead me to a brief final discussion of speciation’s possible role in the spread of the higher intellectual functions.

Structuring as a Candidate for the Big Difference

We tend to think that there was a gradual development of novel vocalizations and words for over a million years or more.  And there were likely even short sentences like our two-year-olds produce (for which you don’t need structure to understand their meaning).   Eventually the long sentences of structured language (and thought) developed - perhaps gradually, perhaps more suddenly.  A great deal of what’s important for language doesn’t involve syntax, but structuring really makes long sentences fly, and likely complicated thoughts as well.

            There are certainly major predecessors to structured language.  Body postures communicate mood and intention (dogs communicate dozens).  Arm or face posture sequences provide even more bandwidth for broadcasting your feelings and intentions, when trying to persuade others to do things your way.

            Species-specific vocalizations get a big addition from culturally-defined “words” (whether gestural or spoken), whose learned meaning depends much more on context for their interpretation.

            Next come word combinations, such as short sentences, of the 2-yr-old variety.  So far we’re mostly talking about what in 1990 Derek Bickerton called “protolanguage” and this unstructured language (you can guess the meaning without any help from word order or inflections) is what you see in toddlers and speakers of pidgins.

            Long sentences, however, are too ambiguous without some mutually understood conventions about internal structuring into phrases and clauses.  A clause with its verb may be embedded in a phrase, and vice versa, ad infinitum.  Such conventions constitute syntax and each dialect has a different way of doing things.  “Universal grammar” highlights the tendency of all human groups to use a restricted set of structuring possibilities; not every scheme is possible, and that restriction likely has something to do with the way in which the average human brain is wired.

            Once you have a syntax (kids most obviously pick them up in the second year, and start producing longer sentences between 18 and 36 months), you can convey complicated thoughts.  And hopefully think them first, so as to avoid that blues lament of Mose Allison, about when “Your mind is on vacation but your mouth is working overtime.”  It is this last step up to syntax that is the usual candidate for the mind’s big bang, not the language-lower-case stuff that, though essential, falls short of capital-L Language per se.

       But the mental machinery for syntax is likely shared, at least in part, with other things that require some structuring. 

1.      planning for uncertain futures (not just the seasons) and their associated agendas (contingencies are structuring)

2.   logical trains of inference that allow us to connect remote causes through intermediate stages to present effects (and a propensity to guess at chains of causation, useful both for doing science and for fooling yourself).

3.   games with made-up rules (hopscotch, not just play) and dance,

4.   our fascination with discovering hidden patterns, seen in music (not just rhythm but four-part harmony), crossword puzzles, and doing science.

And perhaps the mental machinery is shared in part with some nonintellectual functions as well, such as

1.      accurate throwing (not just flinging, which many chimps do, but practicing to hit smaller and smaller targets),

2.   extensive tool making (especially tools with which to make other tools - multiple stages again, like prepared cores),

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 for the Nth time.  Novel structured stuff is what we usually call “higher intellectual function.”

            Whatever economist said that “There are no free lunches” obviously didn’t read Darwin and his successors.  Pay via natural selection for one functionality like planning or language, and you may get the others like music mostly “for free.”  Not only is there is a great deal of multiple use in evolution but you can see a low-tech reminder on many a street corner.  Those curb cuts were paid for by the wheelchair considerations but such “wheelchair ramps” are largely used - and for free - by suitcases and skateboards, bicycles and tricycles.

            The free uses may, of course, pay for subsequent improvements.  I can remember the traffic jams that used to occur at the wheelchair ramps at airports, as the wheeled suitcases all queued up, awaiting their chance at the slot - this resulted in making curb cuts as wide as the crosswalk.  So we see how one secondary use did eventually pay for additional improvements.  When robotic developments enable both wheelchairs and suitcases to climb seven-inch-high stairs, they'll find curbs easy.  The curb cuts may become obsolete for their original functions, though still frequented by bicycles and skateboards.

            But the point remains:  secondary use initially gets a free ride, and any improvements don’t necessarily displace the primary use.  The structure remains multifunctional.  The name changes to reflect the most obvious high-order use - and since the brain is very good about multiple use, maybe our high-order uses ought to be seen in this curb-cut context.  All this is, of course, meant to be a parable:  I want you to see the story of complex thought as a parallel to curb-cut uses.  Bickerton and I address some of the possible preadaptations for syntax in our Lingua ex Machina book.  As Liz Bates is fond of saying about so-called language cortex, these areas seem to have “kept their day jobs.”  They haven’t turned pro, true specialists like the neurosurgeons who have forgotten how to deliver babies.  And I would add that some of the secondary uses of the shared mental circuitry, like logical chains of reasoning, are so amateur that maybe they too are not ready for prime time, that we’re winging it, in relying so much on them.

            At the short-sentence stage of protolanguage, the speed of articulation or the duration of the speech buffer may not be important - though I think that Phil Libermann’s argument does apply later on.  Instead, I like 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 complex novel sentence aloud, no one might be able to interpret it, without thinking about it overnight.

            So conversational language may not have been the first “killer application” of structured thought.  It could have been something closer to the contingency or precision aspects of plan-ahead (“planning first, repartee last,” I call this scenario) - and, of course, if you want to speculate about the “wheelchair” that initially paid for it, remember that accurate throwing requires an exquisite amount of planning, that it has big immediate payoffs in terms of high-calorie meals - and that if you miss the first time, dinner runs away.

What was thought like before structuring?  

            People love to speculate about what life was like “before modern consciousness.”  It isn’t just novelists.  The archaeologist Steven Mithen speculates about how Neanderthals thought, recalling Dan Dennett’s description of “rolling consciousness” without memory storage, the sort of thing that allows you to drive a car and carry on a conversation at the same time, but not be able to recall the stop signs along the route.  One of the reasons that paleo­anthropologists like Ian Tattersall like to talk about consciousness kicking in at 40,000 years ago is that modern humans then seem so much more capable of high-end functions.

            Personally, I hate to use the C word and other such big, loaded words to describe things that I think of in more textured, fine-grain terms.  Many of you will recall that quip by Francis Crick, about the border between the living and the inorganic, which used to be a big dichotomous debate.   Well, said Crick, the boundary disappeared into so much molecular biology - and the same thing was going to happen to consciousness as a concept, that it would disappear into so much neurobiology.  But I do think the archaeologists and paleontologists are all on to something, whatever they call it in their groping around for mechanism and metaphor, and that it perhaps points to the structuring of thought.

            We have trouble thinking about unstructured thought because we can do it so effortlessly.  I may be forced into unstructured language when traveling abroad, but I can still structure the English version before I try to translate it into my halting, agrammatical German-with-gestures.  My purpose here is simply to provide a few examples that might illuminate what mental life might have been like for everyone, all the time, back in antebellum days.

            Thought before structuring might have something to do with what some followers of Freud like to call “primary process” in our mental lives.  The notion is that primary perceptual stuff got an addition called “secondary process.”  Secondary stuff involves symbolic representations of an experience, not merely the primary-process experience itself.  Secondary stuff is capable of being logical, even occasionally achieves it.  Then there are the Piagetian stages.  Their distinctions are hard to summarize briefly so let me stick to the neurologists’ descriptions instead.

            Oliver Sacks’ description of an eleven-year-old deaf boy, reared without sign language for his first ten years, nicely shows what mental life is like, when lacking syntax:

Joseph saw, distinguished, categorized, used; he had no problems with perceptual categorization or generalization, but he could not, it seemed, go much beyond this, hold abstract ideas in mind, reflect, play, plan.  He seemed completely literal -- unable to juggle images or hypotheses or possibilities, unable to enter an imaginative or figurative realm.... He seemed, like an animal, or an infant, to be stuck in the present, to be confined to literal and immediate perception….

Similar cases also illustrate that any intrinsic aptitude for language must be developed by exposure during early childhood.  Joseph didn't have the opportunity to observe syntax in operation during his critical years of early childhood:  he couldn't hear spoken language, nor he was ever exposed to the syntax of sign language.

            Tony Damasio’s extended consciousness, in The Feeling of What Happens, is not explicitly structured, though I think it amounts to the same thing.  He certainly shows us another way to describe the big step up, and rather elegantly at that:

When we slip and say that consciousness is a distinctively human quality, we are thinking of extended consciousness at its highest reaches, not of core consciousness, and we should be forgiven for the arrogance: extended consciousness is indeed a prodigious function, and, at its peak, it is uniquely human.

      Extended consciousness goes beyond the here and now of core consciousness, both backward and forward…. If core consciousness allows you to know for a transient moment that it is you seeing a bird in flight or that it is you having a sensation of pain, extended consciousness places these same experiences in a broader canvas and over a longer period of time.  Extended consciousness still hinges on the same core "you," but that "you" is now connected to the lived past and anticipated future that are part of your autobiographical record.  Rather than just accessing the fact that you have pain, you can also survey the facts concerning where the pain is (the elbow), what caused it (tennis), when you last had it before (three years ago, or was it four?), who has also had it recently (Aunt Maggie), the doctor she went to…, the fact that you will not be able to play with Jack tomorrow.  [pp.195-6]

Damasio’s focus is not on the higher intellectual functions (indeed, he treats language only briefly).  But note that his enhanced detail and time span of extended consciousness likely could not be achieved without an equivalent in thought of Bickerton’s long sentences.  I’ll bet that in Damasio’s extended consciousness, you still need phrases and clauses that can have a life of their own and combine in different ways.  In short, extended consciousness likely needs syntax’s structuring aspect, even without overt planning or speech, just to keep mental life from blending everything like a summer drink.  And getting muddled when more than maybe three concepts have to juggled at the same time.

            Now that I’ve explained what I mean by structured thought and life without it, let me turn to the two remaining questions:  What are the gene-specified neural mechanisms coming into play?  And what are the roles played by speciation and by cultural spread - might culture alone suffice to explain the Mind’s Big Bang, even with old genes?

            Let me briefly tackle the culture-alone possibility.  Most things are nature and nurture, genes and culture - and chances are that the 40,000-years-ago happening is both a change in gene combinations and cultural spread amplifying it.  But sometimes, as with the invention of reading and writing 5,000 years ago, culture alone likely did the whole job, building on preexisting genes already in use.  What someone needs to do is to rough out a culture-alone candidate for the rapid emergence of syntax and complex thought, against which we can judge the new-gene-combination candidates that we so readily concoct.  I’m trying to do just that for a book manuscript in progress, but there isn’t time here to flesh it out.  So I’m going to stick to giving you two examples of how subtle genetic changes might have triggered the efflorescence of tool-making and art-making, and then consider how speciation prevents backsliding and conserves progress.

What brain mechanisms might kick in,
to produce the efflorescence?

          One of the simplest changes you can make is in a behavioral predisposition:  Loner vs gregarious.  Propensity to share food.  Liking to dig.  Liking to throw.  Hoarding.  Acquisitiveness is the concept which I have applied (it’s somewhere in Lingua ex Machina) to how the human infant builds a language machine by listening for patterns.  First, infants begin forming up categories for the common speech sounds they hear, not whole words so much as the little units we call phonemes, less than a tenth of a second in duration.  Categories allow them to generalize across speakers, so that the mother’s /ba/ sound and the father’s somewhat deeper /ba/ sound are treated the same despite their differences.  By about a year of age, babies stop hearing many of these differences, having standardized them.

            By a year of age, babies are discovering patterns in the strings of phonemes and acquiring six to nine new words every day, just from the examples they hear (long before they begin speaking them).  The words acquiring meaning, the phonemes remain meaningless.  You can say kids are like ‘sponges’ soaking up words but that’s too passive a notion, one of the reasons I prefer the more active ‘acquisitive’ as the characterization. 

            So kids have pyramided words atop the phonemes, and now have compound structures made from building blocks.  But then they do it again, discovering patterns in the strings of words they hear and inferring the grammar of that particular language:  ways of making plurals and past tenses and nested phrases.  This happens between the ages of 18 and 36 months.  Then they’re off detecting patterns on even longer time scales, that of the collection of sentences we call a story.  They infer that a satisfying story has a beginning, middle, and a wrap-up ending - and then they start demanding proper endings for their bedtime stories.

            Now you can talk about this as separate instincts for acquiring phonemes, words, syntax, and narrative - or you can try out an overarching principle.  Mine is that it is just repeated instances of pattern-finding acquisitiveness, spanning longer and longer time windows.  It may, of course, turn out to be something of both the general and the specific, but what’s interesting is how much you can buy by just pyramiding ‘acquisitiveness’ concepts four times over.  It’s a pyramid, about like compounding atoms into molecules, molecules into crystals, and then making goblets out of the crystals.

            Acquisitiveness by kids is why there might be more than just cultural spread involved when converting to widespread syntax, perhaps 40,000 years ago.  Yes, I can see acquisitiveness for words per se having been around for a million years or more.  But pyramiding to syntax and then narratives in the preschool years, well before much plan-ahead or accurate throwing develops, happens so reliably in most modern kids that it makes me wonder if that higher-order acquisitiveness is an additional adaptation, perhaps backstopped by a speciation-like event.  That’s one possibility for the efflorescence, not a syntax gene but minor changes in language development via acquisitiveness changes of some sort, maybe just by change timing of staging in development.

            Now let me briefly address another suggestion, Steven Mithen’s 1996 notion of connecting mental modules as a source of the mind’s big bang.  It’s in The Prehistory of the Mind but let me quote the summary that Ramachandran made:

“[Mithen] claims that before the big bang there were three different brain modules in the human brain that were specialized for ‘social or machiavellian intelligence,’ for ‘mechanical intelligence’ or tool use, and for ‘natural history’ (a propensity to classify).  These three modules remained isolated from each other but around 50,000 years ago some genetic change in the brain suddenly allowed them to communicate with each other, resulting in the enormous flexibility and versatility of human consciousness.”

As the proprietor of about the only neural-circuits theory for how novel long-distance cortical interconnections might improve dramatically (and without any further brain enlargement or reorganization, at that), I find Mithen’s notion appealing (though not his specific compartments; he seems to have learned his neuroanatomy from Jerry Fodor).

            But better interconnections fits very well with the second half of my 1996 book, The Cerebral Code.  It addresses the subject of rapid, on-the-fly communications between distant cortical areas - and how to make a big improvement in them.  The problem is how to do long-distance communication in the cortex without a slow learning procedure for each new novel combination.

            I suggested that the improved interconnections between areas briefly occur when the anatomically-incoherent corticocortical interconnections (lots of jumble and blur) finally become temporarily coherent via a physiological workaround involving sufficient redundancy.  With such a plainchant chorus of sufficient size all singing the same little spatiotemporal melody, you can recover that novel spatiotemporal firing pattern at the other end and pass it on (see chapter 7 of The Cerebral Code) to a third cortical area, also unaltered.  And even loop back to the original area, with it immediately (without a learning process) able to recognize the message.

            A common code in neocortex would sure make life easier for novelty.  And a Darwinian process of the kind I describe in the Cerebral Code - which is where the populations come from that act like choirs - sure helps eliminate the nonsense and make the good even better.

            That ability to routinely handle novelty, dependent on finally reaching a critical mass that allows recovery of the original pattern from the blur and jumble, might well have contributed to the aforementioned Big Step Up.  It would have allowed novel parts, such as phrases and clauses, to each be maintained in their own cortical workspace - while still contributing to a whole somewhere else, such as a sentence with syntax.  A contingent plan, a chain of logic, or a multivoiced musical appreciation also have independent parts contributing to a whole - and often a whole that must be contrasted to other wholes, even compete with multiple possibilities quickly.

            So I wonder if it wasn’t the whole suite of higher intellectual functions that emerged so dramatically 50,000 years ago, not just syntax or complex thought.  Other things, like buffers and speech speed, and certainly augmented imitation abilities, might have helped.  Indeed, mirroring novel sequences, as in learning how to dance by mimicry, may have been the key to spreading structured language around the world so quickly, just as a cultural conquest.  

Speciation and the Emergence of Higher Intellectual Functions  

This step up, remember, is from protolanguage with lots of vocabulary and novel short sentences, not all of the way up from the associative memory abilities of chimpanzeelike creatures.  But the inflammation of protolanguage into red-hot syntax may not be the complete answer.  As I noted earlier, kids today are extremely acquisitive of phonemes, then words, then syntax, and then narrative.  This suggests that some behavioral adaptations have been operating, perhaps with the aid of ratchets that protect against backsliding.

            So let me revisit the old what’s-a-species issue.  You can have physiological speciation (poor interbreeding between populations) without the obvious gross anatomical changes that paleo­anthropologists would be comfortable labeling a new species. As Ian Tattersall points out, there have likely been many times more “physiological” speciation events than we could infer from the bony-anatomy ones seen in the fossils.

            What is speciation good for, anyhow?  It preserves progress.  It keeps things from backsliding, that’s what.  To understand speciation, think small.  Accumulating some physical differences is much easier in an isolated small population with no gene flow into it, say on an island.  The local environment can really “select for” those variants which fit it.  Similarly, sexual selection’s peculiarities like peacock tails can also get going most easily in small situations.

             But when the climate improves, facilitating travel, some immigrants arrive from a larger population elsewhere.  This dilutes whatever adaptations might have been achieved locally (which is one definition of “progress”).  “Genes for cooperation,” for example. might have increased to involve half of the small population but then the percentage backslides with the dilution.  The locals become more average.

            That’s adaptation.  Speciation is quite another matter, sometimes due to chromosomal peculiarities as in the horses, sometimes to shifted breeding seasons as in the Grand Canyon squirrels, sometimes to mate selection peculiarities such as males that don’t dance well enough to get an invitation to mate.  The high spontaneous abortion rate in humans (80 percent of all conceptions are flushed in the first six weeks -- the rate is very low in domestic animals like horses and cattle) holds a lot of possibilities for speciation because if something raised it to 98% between groups, that would effectively create a barrier between the populations.

            So you have to distinguish between the evolution of physical differences in a regional population (that’s “adaptation”) and the reproductively isolating mechanisms which occasionally preserve those physical differences (that’s “speciation”) from the usual back-and-forth mixing.  One usually doesn’t produce the other, but sometimes they coincide.  It’s much like trying to cross a two-way street, waiting for gaps in the traffic.  A gap in one lane doesn’t help much, so you await simultaneous gaps before crossing.

            It is when adaptation and speciation coincide that life undergoes sustainable change (though most new species promptly go extinct, just because small populations are more likely to be wiped out in the downsizing caused by the next drought).  It’s the disruption of reproductive continuity that allows regional physical differences to accumulate, protecting them from dilution, much as a ratchet prevents backsliding.

            Once two populations become reproductively isolated (“the species has split into two”), then they tend to compete with one another.  Yes, they might ignore one another like two ships passing in the night, just a wave in passing, or they might even cooperate in some matters, but if they utilize much the same resources (food, nesting places) and have similar predators and parasites, then one of the species is likely to fare somewhat better than the other.  That’s all that “competition” really means - though, of course, competition between populations can also include the bloodier forms.

            So that’s the sort of thing that might have preserved innovations at the Big Step Up.  While some modern mental abilities become apparent in art and toolmaking between 50,000 and 35,000 years ago, it’s not clear yet how fast they spread -  whether there was enough time for gene flow to operate, as in the two Out of Africas, or whether cultural spread did the job.  Furthermore, the Y chromosome data suggests a population bottleneck about 50,000 to 40,000 years ago[i], raising the possibility of some late genetic change affecting higher intellectual function - so that the creative explosion might have been spread, in part, by gene spread.

             Maybe new genes appeared on the scene 50,000 years ago.  Maybe not, too – we’re always happy to credit some new gene, but as Ajit Varki points out, it’s even more likely to be the loss of an allele than the addition of one.  But the committee changes, the committee of genes regulating early brain development trajectories and staging, from whence comes the behavioral propensities, and the bigger cerebral choirs, or whatever.  

If our modern life of the mind is less than 50,000 years old, however, it does raise some interesting questions.  The efficiency notions surrounding evolution often lead to generalities about how evolution produces “well-tested” parts - this despite all of the evidence from medicine about how poorly “designed” a lot of important things are, such as the female reproductive tract.

            But when innovations are still young, then all bets are certainly off.  We don’t expect reading to work well because writing has only been around for 5,000 years.  Five thousand years is only fifty centuries and, at four generations per century, that’s a mere 200 generations since writing was invented (and was only implemented in only a few percent of the population, until recent centuries).  No time for adaptations, much less speciation to prevent backsliding.  It’s surprising that 85% of kids who try to read succeed so easily.  That’s all culture operating on some multifunctional brain circuitry.

            Well, 50,000 years is only 2,000 generations and that sure isn’t much time either, but at least a physiological speciation or two seems possible in that period.  The time back to the common ancestor with the chimps and bonobos is, fortunately, a hundred-fold greater span of five million years.  A lot more speciation is possible to protect progress from backsliding, and a lot more multiple use could have developed in brain circuits.

            Gary Larson and the other cartoonists have fun imagining that the other animals think too, but I suspect they’re profoundly wrong, that structured thinking about novelty is one of the aspects of human uniqueness.  And one that evolution hasn’t yet tested very well, one that is clunky - and perhaps dangerous, both to ourselves and the other inhabitants of our planet.


Copyright ©2000 by William H. Calvin, University of Washington, Seattle (

[i] “These results indicate that male movement out of Africa first occurred around 47,000 years ago. The age of mutation 2, at around 40,000 years ago, represents an estimate of the time of the beginning of global expansion.   Russell Thomson, Jonathan K. Pritchard, Peidong Shen, Peter J. Oefner, and Marcus W. Feldman, “Recent common ancestry of human Y chromosomes: Evidence from DNA sequence data,” Proc. Natl. Acad. Sci. USA, Vol. 97, Issue 13, 7360-7365, June 20, 2000.

Ian Tattersall, Becoming Human (1998).

Richard Leakey, The Origin of Humankind (BasicBooks, 1995).

Oliver Sacks, Seeing Voices (University of California Press, 1987).

William H. Calvin is a theoretical neurobiologist, Affiliate Professor of Psychiatry and Behavioral Sciences at the University of Washington in Seattle.  He is the author of ten books, mostly for general readers, about brains and evolution.  The most recent is his book with Derek Bickerton, Lingua ex Machina: Reconciling Darwin and Chomsky with the Human Brain (MIT Press, 2000).  His web site starts at



Related books and their links:

William H. Calvin, The Cerebral Code (1996)

William H. Calvin and Derek Bickerton,
  Lingua ex Machina: Reconciling Darwin and Chomsky with the Human Brain  
(MIT Press, 2000).

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