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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
24.65469°S   15.90924°E    858m ASL
                        Sossusvlei, Namibia
Hominid opportunities in deserts?



We’ve gone from part of the Kalahari Desert, the part with a lot of water passing through and evaporating in Okavango Delta, to a more typical desert farther to the west, one with ephemeral streams lined with a few trees – and almost none elsewhere.  It’s a savanna strip.

     Admittedly, this was a good year for rainfall, but even when it is much drier, the oryx, eland, and springbok (you really have to see the youngsters’ jack-in-a-box act to appreciate the name) thrive here on the valley floors among the sand dunes.  When you fly low over the area, you see a series of dark lines stretching across the light desert floor.  They are dry watercourses.  There is still some water beneath the surface and, even if there isn’t, the nearby plants are good at storing water for the rest of the year.  The leaves of some plants can be crushed and wrung out like a washcloth, yielding a surprising amount of water.

     When the South African paleontologist Elisabeth Vrba told us that there were a lot of new species of antelope appearing back about 2.7 million years ago in southern Africa, one of its prime implications was that it indicated a need to adapt to arid environments.  And today, there are amazing numbers of oryx and the even bigger eland here in the Namib Desert, happily grazing.  There are some small antelope that can forego visits to the waterhole entirely, getting enough water from the leaves they eat.  If we could test antelope for landscape esthetics, they’d probably prefer to look at something like a bush airstrip – a cleared area where predators can’t hide.  And so bush pilots coming in for a landing have to first buzz the airstrip, to chase them away.

     It makes me realize how much meat on the hoof there was for our ancestors to have exploited in arid environments.  If the antelope and the desert elephant hereabouts can adapt to the desert, then they may make it possible for their predators to do so as well.  They just have to patrol the strips, like teenagers cruising those urban strips following highways out into the countryside.  All the resources are along a track, and it’s just back and forth.

     The fauna associated with the small-brained australopithecine fossils indicate a wooded environment; they wouldn’t have liked it here.  The later versions called Paranthropus between 2 and 1 million years ago were sometimes found in wetland environments, as were the earliest Homo species.  It’s Homo ergaster/erectus and later species that are found in extremely arid and open landscapes like this.  It seems pretty clear what they were eating; certainly in South African coast archaeological sites, there are a lot of eland bones.


This place is a desert because, at these southern latitudes, the rains come from the east.  And by the time that they have traversed the whole width of Africa from east to west (we’re just inland from the west coast), it is even more of a rain shadow than Botswana’s Kalahari Desert.  Namibia is one of the driest places on Earth.  Indeed, what moisture Namibia gets often comes from dew, thanks to the fog drifting in off the ocean, much the same as in the coastal regions of Peru on South America’s west coast.  And there is fog here because the cold Benguela current offshore causes the sea breezes to drop below the dew point as they blow in over the cold current.

     This cold current is part of the developing story about how ocean currents and winds rearranged themselves just before the ice ages started.  Strong winds often sweep surface waters aside – I’ll get into the subject when I fly home over the North Atlantic and discuss the conveyor belt for salt and heat – and bring deeper waters to the surface.  Deeper waters are cold; they’re also loaded with nutrients, and so when they get brought up near the surface where sunlight can penetrate, they serve as fertilizer for all the sea life offshore, a whole food chain worth (lots of seals and dolphins and fishermen hereabouts).

     Well, at drilling site 1084, less than an hour’s flying time west of here, the surface waters are about 10°C colder now than they were 3.2 million years ago.  That means some stronger winds have developed in this part of the South Atlantic Ocean.  The big changes were between 3.2 and 2.1 million years ago, in the second half of the Pliocene, just before we start talking about the Pleistocene’s ice ages.  They go in lockstep with the changes in the North Atlantic.  It’s all part of the story about how the ocean and atmospheric circulation rearranged themselves, to plunge us into the fickle climates of the ice ages.  Which we are still in.


Just to prepare you for hominid fossil country (my next stop is South Africa’s caves, then Kenya’s Rift Valley), let me suggest reading an account of how hominid fossils have been found.  I’m particularly fond of Alan Walker and Pat Shipman’s The Wisdom of the Bones which contains the following account of how the first australopithecine came to scientific attention in 1924 and how it was mostly ignored for the following decades.  I always tend to think of the Leakeys’ 1959 discovery of Zinj at Olduvai Gorge as the first hominid skull discovery, but it was only the first in East Africa (and in a stone-tool context).  The Taung skull was actually discovered a quarter-century earlier by workers in a South African quarry, but dismissed by experts as some sort of ape: 

It is a classic story of anthropology, all the more engaging for being true.  With unerring timing, the box with the missing link in it turned up as [Raymond] Dart was dressing, in wing collar and morning dress, to serve as best man and host for a friend's wedding.  The men from South African Railways who staggered up to the house that summer day in 1924 left two large crates blocking the stoop shortly before the guests were to arrive. Dart had them moved to the pergola, where they would be out of the way, and left off dressing to find a crowbar to pry them open.  The contents of the first box were uninteresting scraps of fossil eggshells and turtle scutes (the bony plates that underlie the turtle's shell).  On the top of the rubble that filled the second crate, Dart spied an extraordinary thing: a natural, fossilized cast of the brain – an endocast. It was of some creature whose brain was about as big as that of an adult chimpanzee.  From his work with Elliot Smith, Dart immediately recognized that this was no ape endocast (unparalleled as that would have been), but one with distinctly human anatomy.  He rummaged through the box frantically and found a piece of bone, covered in rock, into which the endocast fit.  And then real life intervened.  The groom appeared, anxious that Dart should brush the dust off his suit and struggle into his stiff collar; the wedding party was arriving momentarily.  Dart took these two precious pieces of our ancestry and locked them in his wardrobe, reluctantly abandoning them until the festivities were over. . . .

     Dart's precious find was not only overshadowed [first by the Piltdown hoax and then by Peking Man], it was literally abandoned – left, in its humble brown-paper-covered box, in the backseat of a London taxi by Dart's wife.  It was recovered only after frantic searching.  Dart gave up on plans to publish a monograph and returned home, discouraged and defeated.  He gave up fossil work for many years and subsequently suffered a nervous breakdown.  For years, the Taung child sat, forgotten, on Dart's colleague Gerrit Schepers's desk at Wits. . . .


Notes and References
(this chapter
corresponds to 
pages 96 to 101 of the printed book)

Copyright ©2002 by
William H. Calvin

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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