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William H. Calvin, A Brain for All Seasons:  Human Evolution and Abrupt Climate Change (University of Chicago Press, 2002). See also

copyright ©2002 by William H. Calvin
ISBN 0-226-09201-1 (cloth)    GN21.xxx0     
Available from or University of Chicago Press.
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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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To:                  Human Evolution E-Seminar
From:             William H. Calvin
51.3°N     1.4°E     -40m ASL
Down among the fossils

Subject:            All of those chimp-human differences

Hurrying through the fossils at eighty miles per hour, I can’t see a thing except for some little lights that go by every two seconds, serving to reassure you that the train hasn’t stopped somewhere beneath the ocean.  A train usually jerks around enough to reassure the passengers that it hasn’t stopped, but this undersea railroad is pretty smooth.  I’m en route to a meeting in Paris, so you get my third installment for our virtual seminar from a tunnel (“the chunnel”) that is 40 meters beneath the English Channel connecting Folkestone, England, with Calais, France.

          Thinking back to the Sand Walk, I now realize that we often make mistakes in science by making logical but erroneous extrapolations.  For example, “It’s just a drop in the ocean” doesn’t always scale up.  We assume that oceans mix and dilute anything added, despite the evidence that oceans stay poorly mixed (and thus stay cold in the depths) because of dynamic processes that circulate in “streams” more quickly than diffusion can be effective.  This is of some importance; were the depths to start warming up, CO2 would come bubbling out just like from an uncapped bottle of seltzer.  It would, of course, add to the greenhouse effect.

          We don’t scale up time very well either, which is why Darwin and the geologists of the nineteenth century had such a problem convincing nonscientists about the time scale of evolution.  And they worked so hard in selling gradualism over eons that today, when we first begin to think about evolutionary change, we often assume that it is just like when you slide a cardboard box down a loading ramp.  It doesn’t accelerate very much by the time it reaches the bottom; it’s not too different from pushing it across a horizontal floor.

          But every beginning physics student soon learns how different fast dynamics is from slow statics.  Process becomes important and oscillations may occur, as when a pendulum converts kinetic and potential energy back and forth.  In nonlinear systems, dynamics is further complicated because there are often modes of operation, with change-of-state transitions between them that require a story of their own.  The latent heats of the solid-liquid-vapor transitions are the best known – and appearances can fool you.  A cloud layer on the lee side of a mountain may look perfectly static, but it is really forming by condensation at the bottom (which heats the water droplets) and evaporation at the top (which cools them), with a constant flow of water up through the cloud.  The cloud is just an emergent property, its thickness a consequence of those change-of-state transitions.

          For a century, we tried to pretend that evolutionary transitions were just like that box slowly sliding down a ramp, where a slight imbalance of forces operated slowly.  But change-of-state transitions may become far more important than the longer-lasting states.  For example, animals must survive and reproduce during a chaotic climate transition, when all of their hard-earned efficiency adaptations to a particular environment have just become worthless and a new regime hasn’t yet been established. 

Oops, we’ve popped out into France in a mere twenty minutes.  Farther up the French coast is one of the German V-2 rocket-launching sites, made into a museum explaining how Hitler planned to invade Britain.  Apropos of whether scientists are seen as saviors or serpents, I am reminded of Tom Lehrer’s famous satire on scientific responsibility, “Once the rockets are up / Who cares where they come down? / That’s not my department / Says Wernher von Braun.”

          This part of France looks suspiciously like Kansas – I confess, I graduated from a Kansas high school, and learned my evolution later.  Hereabouts, the farm buildings have nice red tile roofs.  Improbably, there are two-story-high earthen berms along the railroad’s right-of-way wherever there is a nearby barn.  These artificial hills deflect noise upward, perhaps keeping the cows from being disturbed by the noise of the Eurostar trains.

          I’ll get to ancient climate presently, but first I thought that I’d do a little stage-setting for this virtual seminar, a shopping list of desiderata.  Since I don’t want you to get too focused on higher intellectual functions (skimming the cream is, in general, a bad habit), this will be a short list of all the major behavioral changes since our last common ancestor with the chimps and bonobos, 5-6 million years ago.

          Mine are all major improvements that need an evolutionary explanation for how we got beyond a great-ape level of abilities in so short a time.  They are things like extensive altruism – not just the sharing with relatives that genes-in-common can help explain, but the sharing with (and taking risks to come to the aid of) strangers, where the giver gets paid back (if at all) by some third person.  Also, things that develop trust among individuals in large groups who don’t all know one another – a prime example is the worldwide scientific community. 

Sharing and cooperation may be good for the species in the long run, but evolution has no known foresight mechanism.  This means that every little increment has to pay its own way with immediate advantages.  It’s difficult even to explain an in-between stage, reciprocal altruism – that’s where you’re doing favors for unrelated friends – because the entry-level stages of it are so easily swamped by freeloaders who receive without giving back.  It’s leaky, like a tire that sinks after a while.

          Yet some reciprocal altruism exists, in chimps and bonobos,  and our ancestors developed altruism more generally into disaster relief, welfare, and peacekeeping forces.  How was such altruism bootstrapped up, through a series of stages with intermediate payoffs?

          Similar questions apply to other beyond-the-apes abilities that we have.  Yet, compared to stones and bones, such issues can be confusingly abstract, and so we tend to focus on “hard evidence” like the hip-and-knee rearrangements needed for upright posture.  Or the big increase in brain size.  We can, however, infer a lot of behavioral changes, just by comparing our fully-human abilities with the versions seen in our closest cousins.

          So here’s my most recent attempt at a hominid bootstrap list, for what happened along with upright stance and enlarged brains.  In my opinion, the big beyond-the-chimps improvements that need step-by-step bootstrap explanations covering the last five million years are:

·         altruism (beyond chimp-level reciprocal altruism),

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

·         extensive tool making (especially tools with which to make other tools),

·         protolanguage (real words used in short combinations, such as the language of two-year-olds),

·         structured language (long sentences with recursive embedding of phrases and clauses, likely a different evolutionary problem),

·         planning for uncertain futures (not just the seasons) and their associated agendas,

·         logical trains of inference that allow us to connect remote causes with present effects (and a propensity to guess at them, useful both for doing science and for fooling yourself),

·         ethics (which may require an ability to estimate the consequences of a proposed course of action, and judge it from another’s standpoint),

·         concealed ovulation (the disappearance of obvious “in heat” periods tended to force males into prolonged sharing with a female and her previous offspring, just to be around at the right time),

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

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

·         our extensive offline creativity (an ability to speculate, to shape up quality by bootstrapping from rude beginnings, yet without acting in the real world).

You’ll notice that I didn’t use the C word here, though I did describe most of the beyond-the-apes uses of consciousness along the way.

          There are many more differences, of course, but I’m trying here for ones with a big order-of-magnitude improvement beyond great ape abilities, the ones which will surely play some prime-mover or hitchhiker role in the evolutionary scenarios that we try to construct for the last five million years.  (Such “uniquely human” lists have proved very useful in the past – because they stimulate ape researchers to disprove them!)

          This isn’t, by the way, a list of “important” things.  For example, dozens of fine primate studies over the last few decades have shown that we share a lot of social behaviors with chimps and bonobos (who have an amazing amount of hugging and kissing, reassuring touches, coalition behaviors, and so forth).  These would make everyone’s list of “important” attributes – and, forty years ago, such things would have made my up-from-the-apes list.  They’re obviously important to “being human” but – as it now turns out –  they may not be order-of-magnitude advances beyond those of five million years ago.  My list is a differential view (as it were, subtracting apes from humans), not the grand view.

          Yes, that’s a rather concentrated list, rather like a five-course French dinner stuffed into a small take-out box.  My sympathies.  But you get a week to dissect and digest it while I soak up some more linguistics and archaeology in a dim classroom in Paris, the variety with hard seats to keep the students awake.  You can argue among yourselves about possible additions to, and subtractions from, my list.  It’s a game anyone can play.

Several minutes ago, we were in farmland, and I was puzzled at why the other passengers were putting their coats on.  Well, I just looked up again and I don’t think we’re in Kansas anymore.  That’s Paris out there.  The Eurostar train isn’t that fast.  It’s just that France has some well-delineated urban areas that lack the usual sprawl of many other cities, the strips extending from the core along the traffic arterials, so like the way that invasive cancers spread along arteries, veins, and nerves.

          The French, at least in places, have learned to deal with that urban form of cancer.  Maybe they will build berms someday to protect people in the cities from the train’s noise, now that they have set a precedent with consideration for the cows.



Notes and References
(this chapter
corresponds to 
pages 27 to 33 of the printed book)

Copyright ©2002 by
William H. Calvin

The nonvirtual book is
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All of my books are on the web.
You can also click on a cover for the link to

Conversations with Neil's Brain:  The Neural Nature of Thought and Language (Calvin & Ojemann, 1994)

The Cerebral Code:  Thinking a Thought in the Mosaics of the Mind (1996)

How Brains Think:  Evolving Intelligence, Then and Now (1996)

Lingua ex Machina:  Reconciling Darwin and Chomsky with the Human Brain (Calvin & Bickerton, 2000)

The six out-of-print books are again available via Authors Guild reprint editions,
also available through (click on cover):

Inside the Brain

The Throwing Madonna:  Essays on the Brain

The River That Flows Uphill


The Cerebral Symphony

The Ascent of Mind

How the Shaman Stole the Moon