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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

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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
2.99599°S   35.35348°E   1480m ASL
                        Olduvai Gorge
Degrees of Separation


Though the Taung child’s skull and brain endocast was the first fossil hominid of distinction, its discovery in 1924 was not heralded by National Geographic photographers and television reporters.  It wasn’t in a stone tool context, and it was ambiguous because the juvenile skulls of closely related species look so alike.  One wanted a better-differentiated adult to see what it really looked like, an ape or something more human.

       To most people who don’t know the Taung history, Olduvai Gorge is where the first hominid skull was discovered in 1959.  That’s certainly what I thought because later in that year, when Louis Leakey was showing off their finds in the U.S., he came to visit the graduate anthropology seminar that I was taking.  Out of his pocket, he pulled some stone tools and several absurdly large teeth and handed them to me, one by one.  They were probably only casts of the true fossil teeth, of course, but I couldn’t tell – I was a physics undergraduate who had talked myself into Melville Herskovits’s famous course without ever having taken the introductory anthro courses.  “Man the Toolmaker” was the motto back then, and as we handled the evidence, we caught Leakey’s enthusiasm for finding a place where some of the pieces might fit together, in the walls of Olduvai Gorge.

AS YOU DRIVE WEST DOWN FROM NGORONGORO in the crater highlands, you come to Olduvai, a gorge with layers exposed that go back 2 million years.  Higher up its walls are lots of handaxes.  No wonder Louis and Mary Leakey were attracted to Olduvai.  They reasoned that the stone tools they found here made it likely that they would eventually find some of the bones of the toolmakers.  And after several decades, they found a skull here in the bottom layers, one with such large teeth that he was sometimes called Nutcracker Man.  Ironically, Zinj now turns out to be one of the hyper-robust australopiths, and thus not so likely to have been one of the better toolmakers.  The second irony is that the vindicated Taung looks more like us than Zinj.  Indeed, with its concave face, Zinj is now considered one of the strangest-looking hominid skulls of all.

       A lot has been learned since 1959 at Olduvai.  While it bottoms out at about 2 million years, Laetoli, 45 km to the south, has earlier layers – including the volcanic ash fall that preserved 3.56-million-year-old footprints of several bipedal apes.  I was happy to see the Gorge Museum and the Zinj discovery site, especially after discovering how few tourists in Kenya seem to be interested in the paleoanthropology; our very experienced Kenyan guide had never had occasion to go to either Olorgesailie or Kariandusi.  The tourist booksellers confirmed my suspicion:  big game and birds rank far higher for tourists than some of the world’s very best sites for showing the epic story of becoming human.  If Olduvai were not on the road from Ngorongoro to the Serengeti, I wonder how many people would go out of their way to visit it.  But then half of Americans still think that humans lived at the same time as dinosaurs, a little error of 65 million years.

Olduvai Gorge

JUST SOUTHEAST OF NGORONGORO is Lake Manyara, a modern lake much like “Lake Olduvai” used to be when Zinj was around.  It’s in the rift valley and, as you drive down the brushy escarpment, passing a variety of baobab trees, you see the complete range of hominid habitats during evolutionary time as you near the lake.

       Near the springs where groundwater from the crater highlands emerges from the hillside, you see forest.  Thanks to reliable shade in this forested band, the direct sunlight in the dry season does not readily bake all of the moisture out of the soil.

       Downhill, with less water, the trees thin out.  Aided by the elephants that knock down trees and create clearings, there is an open woodland where giraffes browse the treetops.


       Finally, there is a savanna of grass near the lake, with only the occasional tree for shade or refuge. 

       Apes mostly live in forests (and occasional swamps).  Before about 1.8 million years ago, hominids lived in the open woodlands, not the savannas.  They probably dug out a lot of roots and potatolike “underground storage organs” not found in forests; in woodlands, their moisture is needed to get through the dry season.

       It was only later that hominids made their living out on the savanna with regularity.  And they probably weren’t eating grass.

Wildebeest in Ngorongoro Caldera

JUST SOUTHWEST OF NGORONGORO is where the Hadza live, downhill around Lake Eyasi. The Hadza are still a hunting and gathering people, one of the last ones left.  They have no system of chiefs, no permanent villages.  They roam the swamps and forests hunting small game (mostly alone, though they may occasionally cooperate when tackling a whole troop of baboons at once), gathering roots and tubers, living in small camps of a dozen or two and moving on every week or so.

       They speak a click language like that of the Kalahari San people a half-continent to the south, have a small pygmy-like stature despite a good diet, but look somewhat like the Arabs who spread down the coast via Somalia.  It is hoped that their DNA will help clarify their roots.

       They are surrounded by cattle herders and fledgling agriculturalists of other tribes, speaking very different languages, people who are busy burning the forests to clear the land for grass or crops.  The Tanzanian government, a few decades ago, tried to give the Hadza some cleared land, livestock, grain, and tools – but in less than a generation’s time they fled back to their traditional swamps and forests.  Soon the Hadza’s traditional way of life, thanks to their progressive neighbors, will vanish, leaving them without heritage or hope.

       The Hadza give us a rare view of how life can be lived without much planning or agriculture, without chiefs, without a settled existence.  While there are a few degrees of cultural separation between the Hadza and the Tanzanian city-dwellers, the Hadza are behaviorally modern:  their art is body decoration and perhaps some cave paintings, their language is elaborate, and they play games with rules.

       We can try to imagine the Hadza without modernity, sitting around skillfully-lit campfires pounding roots and sharpening stones, perhaps speaking the short sentences of a modern two-year-old – but without storytelling, gossip, and gambling, without showing much concern for the past or future.  And in doing so, we can perhaps approximate what Homo sapiens was doing with a modern-sized brain in Africa in the 100,000 years before Africans invented (or evolved) behavioral modernity and spread into Eurasia.  More later.

AFRICANS WHO GET GOOD EDUCATIONS and are encountered in their roles as pilots, professors, and neurosurgeons show that the biological basis is there for doing the things that the Out of Africa peoples do so well, around the rest of the world.  Within Africa, raised one way without much western-style education and then forced to deal with a technological culture in order to support their families, they may not show those strengths, for all the reasons that Peter Mattheissen wrote about in The Tree Where Man Was Born as he described the old colonial days: 

It is often said that Africans cannot lay straight paths or plow straight furrows, screw bottle caps, use rifle sights – in short, that they have no sense of geometric order, much less time, since there is nothing of this sort in nature to instruct them. “Have to watch these chaps every minute,” white East Africans will tell you. “Can’t do the first thing for themselves.”  But perhaps the proper word is “won’t.”  Most Africans are so accustomed to having decisions made for them…, and to carrying out instructions to the letter to avoid abuse, that only rarely do they think out what they are doing, much less take initiative.  Rather, they move dully through dull menial tasks – working automatically, without thought, may be all that makes such labor bearable – preferring to be thought stupid than to get in trouble, and at the same time gleeful when calamities occur.  Stubborn, apathetic, and perverse, they observe the letter of their instructions, not the spirit of them . . . .  Even among white East Africans and black who converse easily in English or Swahili, the problem appears to be mutual boredom, which comes about because both find the interests of the other trivial, and their ideas therefore of small consequence.

Dated though this is, I bring it up because I worry that much of the world could become like that, a world where most of us will not have the education to know how things work – that we will become trapped in a world where you have to wait for someone knowledgeable to tell you what to do next and are thus unable to undertake initiatives on your own.

       One of the shocks, in talking to Kenyans, is discovering that basic education is not a given, that parents must pay to send a child to grade school.  And, being so labor intensive, the good schools cost dearly.  Elsewhere with free public schools, an expensive private school may be nonetheless considered the only way for children to be properly prepared for a fast-paced world.  And so the rich get richer, and the poor get poorer.

       It takes a heavy commitment to quality education for all to avoid that stratification of society, those needless degrees of separation.  But even the present-day United States has lost what commitment it used to have to free education of high quality.  Anyone reading the annual surveys of science literacy (another example:  fewer than half of Americans know that the earth orbits the sun once a year) has to wonder how badly most people are going to be left behind, further along into the 21st Century, whether they too will become “stubborn, apathetic, and perverse” toward a scientific and technological world they must view as magical, beyond their comprehension, accessible only via the right incantations.

THERE ARE MANY REASONS why public schools are neglected.  The one I find most troubling is a curious aspect of practical genetics, one that an evolutionary viewpoint helps illuminate because it is nepotism at one remove, with all the same long-run disadvantages for the community at large.

       Take two high-IQ parents, say 130 each, and consider their offspring.  While it is true that a child of 150 IQ is more likely to come from such parents, it is also true that their average child may be only 120.  (This statistical law is called regression toward the mean; it also works to bring up children of lower-IQ parents closer to the 100 average.)  This doesn’t apply to particular families, of course, who don’t have a hundred offspring to test the probabilities, but it should collectively apply to the group of parents who send their kids to expensive schools:  on average, their kids will be less amply endowed.

       This is the familiar problem with family businesses and lines of royalty:  the second and third generations often aren’t as smart as the founders.  More intensive education can, of course, help make up for any performance differences between parents and offspring.  In this odd, unexpected way, high IQ parents feel more of a need for private schools for their offspring than do average parents, because they want their children to do at least as well as they themselves.

       The problem is that there is another way of helping the less-well-endowed offspring of those who have made it:  decreasing the competition.  It helps explain the generation-ago puzzle of the mother who was against admitting women to medical school; she thereby helped to double the chances of her on-the-edge son getting admitted.  If there are spaces for only one percent of the population, eliminating females meant that twice as many males made it in.  And who can be sure that their child is in the top one percent?

       Discrimination to reduce the competition works, alas, for any sizeable group.  And while one naturally thinks of the twentieth century racial-religious examples in higher education, it also works with the following group: those who cannot afford private education, but have the talent to compete with those who can.  By slowing down the competition, those well-off (and often influential) parents can help their kids to get ahead.  An easy effortless way of hobbling the competition is to neglect public education.

       This is, of course, not in hardly anyone’s conscious reasoning – it’s not intentional so much as conveniently incidental.  Consciously, it will be all about their admiration for high quality (though not a parent, I regularly visit the private school in Seattle where Paul Allen and Bill Gates went to high school in the 1970s, and it is wonderful to see the educational job done really well, an example for all to emulate).  Perhaps the influential parents will think that they can encourage public school quality via “competition in education” or “accountability” or “testing teachers.”  But good intentions are a tricky thing; when the free schools are hamstrung with regulations and underfunded, the holding-them-back result is much the same as overt discrimination against the group that cannot afford private educations.  You simply get needless stratification.

       If you think quality public education is expensive, consider the costs of ignorance and polarization, of an intelligent underclass that becomes stubborn, apathetic, and perverse.



Notes and References
(this chapter
corresponds to 
pages 169 to 175 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