William H. Calvin, A Brain for All Seasons: Human Evolution and Abrupt Climate Change (University of Chicago Press, 2002), readings and notes. See also http://WilliamCalvin.com/BrainForAllSeasons/notes.htm
ISBN 0-226-09201-1 (cloth) GN281.4 C293
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William H. Calvin
University of Washington
For background reading on climate change in general, there are
two recent books which are especially good.
Neither really explores the abrupt climate flip-flops that I
focus on here, but they are exactly what you might want to give
policymakers to help them sort through the more general issues of
climate change. Anyone
who wishes to speak intelligently about ozone, greenhouse, and El Niño
needs to read both of them.
George H. Philander,
Is the Temperature Rising? The
Uncertain Science of Global Warming (Princeton University
Press 1998). Written
with grace and understatement for general readers, by someone deeply
involved with modeling the climate, it covers much of a Princeton
introductory course in the earth sciences.
Brian Fagan, Floods,
Famines, and Emperors: El
Niño and the Fate of Civilizations (Basic
Books 1999). See also his The Little Ice Age
2000). Archaeologists have this wonderful perspective on what’s
gone wrong in the past, both with climate and human institutions.
are two books on a more direct lineage with this one; although
neither book on anthropology and climate emphasizes the abruptness
aspects, they are much better on the Miocene-Pliocene climates and
the slow aspects of the Pleistocene:
Steven M. Stanley, Children
of the Ice Age (Harmony
1996). Much more on the non-abrupt aspects of anthropology and
paleobiology in the ice ages.
Rick Potts, Humanity’s
Descent (William Morrow 1996).
And for an excellent review of paleoclimate indicators, see
his “Environmental hypotheses of hominin evolution,” Yearbook
of Physical Anthropology 41:93-136 (1998).
is now a new paleoclimate book, by one of the experts on the
abruptness seen in the ice cores, that more directly addresses the
present abruptness issues:
Richard B. Alley, The
Two-Mile Time Machine: Ice
Cores, Abrupt Climate Change, and Our Future (Princeton
University Press 2000). It
is written for nonspecialists (Alley has gotten a lot of practice as
a frequent commentator for Science news articles).
The book contains far more detail on abrupt climate change
than the others. So if you find yourself asking, “But how could they
possibly know that?” you’ll find most of the answers in
Alley’s excellent book. Its
final chapter about the future is conventional economic
extrapolation, not the more relevant perspective of high-risk
management seen in medicine, re-insurance, and disaster planning.
If anyone needs a quick reference about the importance with which the scientific community views the revelations about abrupt climate change, see the Perspectives in the 15 February 2000 issue of the Proceedings of the National Academy of Sciences. In particular, see
Richard B. Alley, "Ice-core evidence of abrupt climate changes," Proceedings of the National Academy of Sciences 97(4):1331-1334 (15 February 2000) at http://www.pnas.org/cgi/content/full/97/4/1331.
For a good textbook on the earth sciences, covering atmospheric
sciences, geology, and oceanography, let me suggest:
Brian J. Skinner, Stephen C. Porter, Daniel B. Botkin, The
Blue Planet: An Introduction to Earth Systems Science, second edition (Wiley 1999).
For the paleoanthropological side of things, there are many
choices. In general,
climate makes an appearance only in its usual
uplift-encouraging-the-savannas role or in the gradualist
simplification of the Ice Ages.
Except within the range of tree-ring dating, events that last
for only a few centuries often cannot be seen in the archaeological
record because of bioturbulence smoothing the record out, and the
abruptness implications of the ice cores have generally not been
digested yet. Besides Potts and Stanley, there are many other excellent
books for general readers about anthropology:
Jared Diamond, Guns,
Germs, and Steel: The Fates of Human Societies
Norton 1997). The focus
is on the last 13,000 years and biogeography’s influence on
Donald Johanson, Blake Edgar, From
Lucy to Language (Simon & Schuster 1996).
Richard E. Leakey, Roger Lewin, Origins
Reconsidered: In Search of What Makes Us Human (Doubleday
E. Leakey, The
Origin of Humankind (Basic Books Science Masters Series
Christopher Stringer, Robin McKie, African
Exodus: The Origins of Modern Humanity (Holt 1996).
Fossil Trail (Oxford
University Press 1995), a history of fossil finding which has
excellent fossil hominid illustrations.
Ian Tattersall, Becoming
Human (Harcourt Brace 1998).
Ian Tattersall & Jeffrey Schwartz, Extinct
Humans (Westview Press 2000).
Alan Walker and Pat Shipman, The
Wisdom of the Bones (Knopf 1996).
The relevant textbooks, both of which cover hominids well, are:
John G. Fleagle, Primate
Adaptation and Evolution, second edition (Academic Press
1999). Has more of the
comparative anatomy perspective of physical anthropology.
Richard G. Klein, The
Human Career: Human
Biological and Cultural Origins, second edition (University
of Chicago Press 1999). Has
more of the cultural perspective of archaeology.
For aspects of the great apes, start with:
Dean Falk, Primate
Diversity (W. W. Norton 2000). Her book is aimed at
anthropology undergraduates, with an excellent glossary.
Frans de Waal, Good
Natured: The Origins of
Right and Wrong (Harvard
University Press 1996). Together
with his other books for general readers, such as The
Ape and the Sushi Master, Bonobo,
Among Primates, and Chimpanzee
Politics, you get a good view of what the ape-human
transition might have been from.
Frans de Waal, editor, Tree
of Origin: What Primate Behavior Can Tell Us about Human Social Evolution
(Harvard University Press 2001).
An excellent, readable collection of chapters by nine
the brain side of things, you will find many of the
references in my earlier books, The
Cerebral Code, How Brains Think,
Lingua ex Machina (with the linguist
Derek Bickerton), and Conversations with
Neil’s Brain (with the neurosurgeon George Ojemann), all
at http://faculty.washington.edu/wcalvin. For
the connection with behavior, see:
Tangled Wing: Biological Constraints on the Human Spirit (W.
H. Freeman 2001).
Especially for evolutionary biology, some
fine writers have also been at work, adding to the books written by
the biologists. It is,
after all, one of the grand stories of all time – and nothing else
makes much sense unless you understand the evolutionary process.
Ant and the Peacock (Cambridge University Press 1992).
Richard Dawkins, Climbing
Mount Improbable (Norton,
Daniel C. Dennett,
Dangerous Idea (Simon
& Schuster 1995).
Jonathan Miller, Darwin
for Beginners (Pantheon
1982 but much reprinted) is a fine place to get up to speed, helped
by the illustrations by Borin van Loon.
Called Introducing Darwin in some editions.
John Maynard Smith and Eors Szathmary,
The Major Transitions in
Evolution (W. H. Freeman 1995).
is Biology: The Science of the Living World (Harvard University Press 1997).
Beak of the Finch: A Story of Evolution in Our Time (Knopf
Understanding Evolution (W. H. Freeman 2002).
Edward O. Wilson,
gradual climate change story, about the only aspect of
climate change that has reached a large audience, is not covered
adequately by the present book.
Few realize how strong the case is for global warming, so let
me repeat here some of the items from the IPCC summary of where
gradual climate change seems to be going, “Climate Change 2001:
The Scientific Basis.”
global-average surface temperature has increased over the 20th
century by about 0.6°C.
it is very likely that the 1990s was the warmest decade and 1998 the
warmest year in the instrumental record, since 1861 . . . the
increase in temperature in the twentieth century is likely to have
been the largest of any century during the past 1000 years.
average, between 1950 and 1993, night-time daily minimum air
temperatures over land increased by about 0.2°C per
decade. This is about
twice the rate of increase in day-time daily maximum air
temperatures (0.1°C per decade).
This has lengthened the freeze-free season in many mid- and
data show that there are very likely to have been decreases of about
10 percent in the extent of snow cover since the late 1960s, and
ground-based observations show that there is very likely to have
been a reduction of about two weeks in the annual duration of lake-
and river-ice cover in the mid- and high-latitudes of the Northern
Hemisphere, over the twentieth century.
has been a widespread retreat of mountain glaciers in non-polar
regions during the twentieth century.
Hemisphere spring and summer sea-ice extent has decreased by about
10 to 15 percent since the 1950s.
It is likely that there has been about a 40 percent decline
in Arctic sea-ice thickness during late summer to early autumn in
recent decades and a considerably slower decline in winter sea-ice
data show that global-average sea level rose between 0.1 and 0.2
meters during the twentieth century.
is very likely that precipitation has increased by 0.5 to 1 percent
per decade in the twentieth century over most mid- and
high-latitudes of the Northern Hemisphere continents, and it is
likely that rainfall has increased by 0.2 to 0.3 percent per decade
over the tropical (10°N to 10°S) land areas.
the mid- and high-latitudes of the Northern Hemisphere over the
latter half of the twentieth century, it is likely that there has
been a 2 to 4 percent increase in the frequency of heavy
precipitation events [thunderstorms and large-scale storm activity].
episodes of the El Niño-Southern Oscillation (ENSO) phenomenon…
have been more frequent, persistent and intense since the mid 1970s,
compared with the previous 100 years.
some regions, such as parts of Asia and Africa, the frequency and
intensity of droughts have been observed to increase in recent
few areas of the globe have not warmed in recent decades, mainly
over some parts of the Southern Hemisphere oceans and parts of
atmospheric concentration of carbon dioxide has increased by 31
percent since 1750. The present CO2 concentration has not
been exceeded during the past 420,000 years and likely not during
the past 20 million years. The current rate of increase is
unprecedented during at least the past 20,000 years.
three-quarters of the anthropogenic emissions of CO2 to
the atmosphere during the past 20 years is due to fossil fuel
burning. The rest is
predominantly due to land-use change, especially deforestation . . .
The entire document is at http://www.ipcc.ch.
When a reference is briefly given as Author (year),
it means that the full reference will be found nearby or in the Recommended
ordinary dry spells such as the summer of 2000, “We have the hottest
driest weather in perhaps 50 years, we have thousands of lightning
strikes an hour, we have 300 new fires
day in the West, largely because of lightning strikes,’’ a senior
forest service official said. Reuters
news story, 27 August 2000, datelined Boise, Idaho, USA.
this brief are seldom detected later by scientists studying the
layers, as the worms churn the evidence, mixing up the layers from an
entire millennium. Such
smoothings make it impossible to tell whether a cooling developed
abruptly or more slowly, and it totally hides many of the century-long
abrupt coolings and droughts, which become little bumps in the record.
Generation: Ovid didn’t
describe ashes in the Assyrian version but Hans Christian Andersen
The Phoenix Bird (1872) version.
Third Chimpanzee (HarperCollins 1992).
the brain enlargement two million years ago, there was a further shift
away from ape-like specializations; marathon-like endurance likely
developed and childhood became even longer.
See Leakey (1995).
Loren Eiseley, The Night Country (Scribners 1971),
p.159. Alley (2000),
Solene Morris, Louise Wilson, Down House: The Home of
Charles Darwin (English Heritage 1998).
Directions to Down House can be found at http://WilliamCalvin.com/bookshelf/down_hse.htm
An excellent biography in two volumes is Janet Browne’s Charles
Darwin (Jonathan Cape 1995, 2002).
For Darwin’s correspondence, see http://www.lib.cam.ac.uk/Departments/Darwin/.
Dennett (1995), p.21.
gait,” see Francis Darwin, “A character sketch by
Darwin’s son,” pp. 88-107 in his The Life and Letters of
Charles Darwin (1887).
is a nice summary of the modern synthesis and punctuated equilibria in
Tattersall (1998), ch. 3.
catastrophes: the impact
catastrophe at 65 million years ago was also a series of events and,
while the extinction of the dinosaurs is one result, the adaptive
radiation of mammals was another.
don’t know who used the phrase first, but George Orwell wrote
“Catastrophic gradualism” in the Common Wealth Review
(November 1945); see Collected Essays, Journalism and Letters,
vol. 4 (Harmondsworth 1978), p.35.
Mayr (1997), p.189.
Burnet, “Empedocles of Acragas” at http://plato.evansville.edu/public/burnet/ch5b.htm.
1838 insight upon reading Thomas Robert Malthus, Essay on the
Principle of Population (1798), is covered in Browne (1995) at
biography of Alfred Russel Wallace is at http://www.wku.edu/~smithch/index1.htm.
are discussed in Richard Dawkins, The
Selfish Gene (Oxford
University Press, revised edition 1989); Susan Blackmore, The
Meme Machine (Oxford University Press 1999); and William H.
Calvin, “The Six Essentials: Minimal Requirements for the Darwinian
Bootstrapping of Quality,” Journal of Memetics 1 (1997) at
My six essentials build on the three which Alfred Russel
Wallace listed in 1875 (“. . . the known laws of variation,
multiplication, and heredity . . . have probably sufficed. . . . ”);
I make explicit the pattern, the work space competition, and the
environmental biases. See
Wallace’s “The limits of natural selection as applied to man,”
chapter 10 of Contributions to the Theory of Natural Selection
a third and a half of an infant’s cortical connections present at
eight months of age seem to disappear by adulthood, although few
neurons are lost; essentially, some axon branches are retracted.
The best data is in monkey:
P. Rakic, J.-P. Bourgeous, M. F. Eckenhoff, N. Zecevic, and P.
Goldman-Rakic, “Concurrent overproduction of synapses in diverse
regions of the primate cerebral cortex,” Science 232:232-234
(1986). But the figure reflects the balance between creation of new
synapses and breaking of old ones – and we don’t yet know the rate
of either creation or destruction, just some estimates of the
cumulative differences. For
all we know, there could be a turnover of five percent every month,
with the rate of destruction only slightly greater than the rate of
creation leading to the observed differences.
are also needed to restore variation to an inbreed population like the
cheetahs who, while they might have gene-shuffling and recombination,
don’t have very many alternative alleles to shuffle.
ocean bottoms remain cold, see Philander (1998), p.128.
A dramatic example of trapped CO2 bubbling out in
the manner of an uncapped bottle of seltzer occurs in volcanic lakes
such as Lake Nyos in the mountainous region of northwestern Cameroon,
where 1,700 people were killed in 1986.
A strong wind causes the stratified lake to turn over; the
gas-rich bottom waters, upon reaching the surface, release their gas
in huge quantities. In
the case of Lake Nyos in 1986, the jet of gas and water shot up about
260 feet. Moving at about
45 miles an hour, the gas reached villages 12 miles away.
The lake released about a cubic kilometer of carbon dioxide.
It is also a sterling example of a recurring natural disaster
that, now that scientists understand its mechanism, can be prevented
via appropriate technology. Michel
Halbwachs, Jean-Christophe Sabroux, “Removing CO2 from
Lake Nyos in Cameroon,” Science 292(5516): 438 (20 April
see the 27 February 2001 New York Times news story, “Trying
to tame the roar of deadly lakes,” at http://www.nytimes.com/2001/02/27/science/27LAKE.html.
through clouds, see Philander (1998), p.84.
For “latent heat,” see the glossary.
Tom Lehrer, see http://www.keaveny.demon.co.uk/lehrer/lyrics
ovulation, see Jared Diamond, Why
is Sex Fun? (Basic Books 1997).
The C word: William
H. Calvin, “Competing for
Consciousness: A Darwinian Mechanism at an Appropriate Level of
Explanation,” Journal of Consciousness Studies
Frans de Waal, Frans Lanting, Bonobo:
The Forgotten Ape (University of California Press 1997) .
For more bonobo information, see http://WilliamCalvin.com/teaching/bonobo.htm.
de l’Homme in Paris
F. C. Chen and W. H. Li, “Genomic divergences between humans
and other hominoids and the effective population size of the common
ancestor of humans and chimpanzees,” American Journal of Human
Genetics 68(2):444-456 (February 2001).
S. L. Page and Morris Goodman, “Catarrhine phylogeny:
Noncoding DNA evidence for a diphyletic origin of the mangabeys and
for a human-chimpanzee clade,” Molecular Phylogenetics and
Evolution 18(1):14-25 (January 2001).
Ragir, “Diet and food preparation:
Rethinking early hominid behavior,” Evolutionary
Anthropology 9:153-155 (2000).
Sonia Ragir, Martin Rosenberg,
Philip Tierno, “Gut morphology and the avoidance of carrion among
chimpanzees, baboons, and early hominids,” Journal of
Anthropological Research 56:477-512 (2000) at http://www.unm.edu/~jar/v56n4.html#a3.
Mark F. Teaford and Peter S. Ungar, “Diet and the evolution
of the earliest human ancestors,” Proceedings of the National
Academy of Sciences (U.S.) 97: 13506-13511 (5 December 2000).
Richard W. Wrangham, James
Holland Jones, Greg Laden, David Pilbeam, and NancyLou Conklin-Brittain,
“The raw and the stolen: Cooking and the ecology of human
origins,” Current Anthropology 40(5):567-594 (December 1999).
B. M. de Waal, “Apes from Venus:
Bonobos and human social evolution,” in Tree of Origin,
edited by Frans B. M. de Waal (Harvard University Press 2001), pp.
Wrangham, Dale Peterson, Demonic
Males: Apes and the Origins of Human Violence (Houghton
E. Reed, “Early hominid evolution and ecological change throughout
the African Plio-Pleistocene.”
Journal of Human Evolution 32:289-322 (1997).
Says australopithecines are found associated with faunas
suggesting wooded habitats.
Coppens, “The East Side story,” Scientific American, pp.
88-95 (May 1994).
out-competing chimps is just the latest version; there used to be lots
more ape species, many more than Old World Monkeys.
But the monkeys have been gaining with the Pleistocene climate
changes, showing that being smarter is not always better. The Uganda story is from Michael P. Ghiglieri, East of the
Mountains of the Moon: Chimpanzee Society in the African Rain Forest
(Free Press 1988).
Leo Gabunia, Abesalom Vekua, David Lordkipanidze, Carl C.
Swisher III, Reid Ferring, Antje Justus, Medea Nioradze, Merab
Tvalchrelidze, Susan C. Antón, Gerhard Bosinski, Olaf Jöris, Marie
A.de Lumley, Givi Majsuradze, Aleksander Mouskhelishvili, “Earliest
Pleistocene hominid cranial remains from Dmanisi, Republic of Georgia:
Taxonomy, geological setting, and age,” Science
288:1019-1025 (12 May 2000).
C. Swisher, W. J. Rink, S. C. Anton, H. P. Schwarcz, G. H. Curtis, A.
Suprijo and Widiasmoro, “Latest Homo erectus of Java: Potential contemporaneity with Homo sapiens in southeast
Asia.” Science 274: 1870-1874 (1996).
scaled-down version of the multiregional hypothesis is Milford H.
Wolpoff, John Hawks, David W. Frayer, Keith Hunley, “Modern human
ancestry at the peripheries: A test of the replacement theory,” Science
291:293-297 (12 January 2001).
Yuehai Ke, Bing Su, Xiufeng Song, Daru Lu, Lifeng Chen, Hongyu
Li, Chunjian Qi, Sangkot Marzuki, Ranjan Deka, Peter Underhill,
Chunjie Xiao, Mark Shriver, Jeff Lell, Douglas Wallace, R Spencer
Wells, Mark Seielstad, Peter Oefner, Dingliang Zhu, Jianzhong Jin, Wei
Huang, Ranajit Chakraborty, Zhu Chen, and Li Jin, “African origin of
modern humans in east Asia: A
tale of 12,000 Y chromosomes,” Science 292:1151-1153 (10 May
2001). “We came to a
simple conclusion,” says Li Jin. “There are no old lineages left
[from archaic Asians].”
One self-described “dedicated multiregionalist,” Vince
Sarich of the University of California, Berkeley, said:
“I have undergone a conversion – a sort of epiphany.
There are no old Y chromosome lineages [in living humans].
There are no old mtDNA lineages.
Period. It was a
Wisteria and Out of Africa, see Kenneth
H. Thieme, “Lower Paleolithic hunting spears from Germany,”
Nature 385:807-810 (1997).
H. Orians, “Human behavioral ecology:
140 years without Darwin is too long,” Bulletin of the
Ecological Society of America 79(1):15-28 (1998).
English landscape architects were good at keeping the large animals in
the distance. They hid a
fence in a “ha-ha,” a ditch through the landscape.
From the customary viewpoint, the viewer didn’t see the
ditch, looking right over the top of it at the distant pastoral
carryover from altruism to syntax:
William H. Calvin, Derek Bickerton, Lingua
ex Machina: Reconciling
Darwin and Chomsky with the Human Brain
(MIT Press, 2000), chapter 10.
C. Brown, Benjamin Thompson, Count Rumford (MIT Press 1979).
per generation: One
sometimes sees 20 years given for the human generation time.
But a reasonable definition is not the shortest possible
interval but the age of the mother at the birth of a child, averaged
over her children that survive. With
menarche at 17 in Sweden only a century ago, and with the first baby
having a lower chance of survival, I’d guess that the average
surviving children were mostly born when the mother was between 20 and
Richard Dawkins, The Selfish Gene (Oxford University
Press 1976), p.214.
Jeremy R. Marlow, Carina B. Lange, Gerold Wefer,
Antoni Rosell-Melé, “Upwelling intensification as part of the
Pliocene-Pleistocene climate transition,” Science
290:2288-2291 (22 December 2000).
C. Aiello, Peter Wheeler, “The expensive tissue hypothesis:
The brain and the digestive system in human and primate
evolution,” Current Anthropology 36:199-221 (1995).
And see Ann Gibbon’s news story, “Solving the brain’s
energy crisis,” Science
380: 1345-1347 (29 May 1998).
one neocortical area, enlarge them all” paraphrased from:
Barbara L. Finlay and R. B.
Darlington, “Linked regularities in the development and evolution of
mammalian brains,” Science 268:1578-1584 (1995).
within and between species: As
my colleague Joe Felsenstein is fond of pointing out (the “coalesce
fallacy”), suppose you have two species A and B.
You plot brain size vs body size for a hundred As, and perhaps
you get a symmetrical scatter with no trend.
Ditto for B, except that Bs are usually bigger than As.
If you mix up As and Bs into one big scatter plot (and don’t
plot the points in different colors), you get an impressive upwards
trend: “bigger bodies
have bigger brains,” someone shouts -
all without being able to see the trend within either species by
itself. Maybe the trend
doesn’t exist at all, and is just an artifact of lumping when you
should be splitting. Actually
bigger bodies within a species usually do have bigger brains, but
there are many situations where lumping groups can mislead you.
Correlation is not causation, and sometimes correlation itself
is – as with lumping the hypothetical As with the Bs –
meaningless. The same
caution applies, say, to plotting brain size vs. IQ scores for
different geographic subpopulations, e.g., races. You need to establish the trend within the subpopulation and
you constantly have to look out for a correlation which isn’t cause
and effect but merely a mutual consequence of some third thing such as
growth rates or hormone levels at critical periods during development.
earlier discussed the r-K spectrum in chapter 6 of my The Ascent of
Mind (Bantam 1990), at http://WilliamCalvin.com/bk5/bk5ch6.htm.
Life history analysis:
Barry Bogin, Patterns
of Human Growth, 2nd ed. (Cambridge University Press 1999).
data in the figure is adapted from figure 8.3 of Klein (1999), which
is based on the 1990 collection of Aiello and Dean.
Kutzbach, G. Bonan, J. Foley, S. P. Harrison, “Vegetation and soil
feedbacks on the response of the African monsoon to orbital forcing in
the early to middle Holocene,” Nature 384:623-626 (19
J. E. Kutzbach, Z. Liu, “Response of the African Monsoon to
Orbital Forcing and Ocean Feedbacks in the Middle Holocene,” Science
278(5337) 440-443 (17 October 1997).
Martin Claussen, Claudia Kubatzki, Victor Brovkin, Andrey Ganopolski, Philipp Hoelzmann, Hans-Joachim Pachur, “Simulation of an abrupt change in Saharan vegetation in the mid-Holocene,” Geophysical Research Letters 26(14):2037-2040 (15 July 1999).
Philipp Hoelzmann, Birgit Keding, Hubert Berke, Stefan Kröpelin
and Hans-Joachim Kruse, “Environmental change and archaeology:
Lake evolution and human occupation in the Eastern Sahara
during the Holocene,” Palaeogeography, Palaeoclimatology,
Palaeoecology 169:193-217 (2001).
Ana Moreno, Jordi Targarona, Jorijntje Henderiks, Miquel
Canals, Tim Freudenthal and Helge Meggers,
“Orbital forcing of dust supply to the North Canary Basin
over the last 250 kyr,” Quaternary Science Reviews 20(12):1327-1339
Hadley, “Concerning the cause of the general trade winds,” Philosophical
Transactions, vol. 39 (1735).
a good explanation of the Coriolis effect, see Philander (1998),
pp.95-98, 234-239. This
is why all ocean currents curve; the only one that seems to travel in
a straight line for a long way is the Equatorial Undercurrent, 100
meters deep beneath the Pacific.
Being at the equator, there is no Coriolis “force” to
S. Broecker, Dorothy Peteet, Irena Hajdas, Jo Lin, Elizabeth Clark,
“Antiphasing between Rainfall in Africa’s Rift Valley and North
America’s Great Basin,” Quaternary Research 50:12-20
the Polar-Ferrel Cells via Gulf Stream
at 60°N: This idea is surely not original to me, but I cannot
find any serious studies of its stabilizing influence, compared
to other (perhaps more important) factors.
Dart, “Australopithecus africanus: the man-ape of South
Africa,” Nature 115:195-199 (1925).
M. Gray, John D. Sheaffer, Christopher W. Landsea, “Climate trends
associated with multi-decadal variability of Atlantic hurricane
activity,” pp.15-53 in Hurricanes: Climate and Socioeconomic
Impacts. (H.F. Diaz and R.S. Pulwarty, eds., Springer Verlag, New
York 1997). See http://www.aoml.noaa.gov/hrd/Landsea/climtrend/.
in drier areas: W. C.
McGrew, P. J. Baldwin, C. E. G. Tutin, “Chimpanzees in a hot, dry
and open habitat: Mt.
Assirik, Senegal, West Africa,” Journal of Human Evolution
10: 227-244 (1981); A. Kortlandt, “Marginal habitats of
chimpanzees,” Journal of Human Evolution 12: 231-278 (1983).
Hominids in arid environments, see Kaye E. Reed, “Early
hominid evolution and ecological change through the African
Plio-Pleistocene,” Journal of Human Evolution 32:289-322
J. M. Diamond, Guns,
Germs, and Steel: The Fates of Human Societies (Norton (1997), p.94.
(1996), p.109. The chimp
subpopulation map is adapted from de Waal and Lanting (1997).
glacial time (and perhaps during the cold flips as well), the tropics
were less wet than now – but some desert regions such as Nevada were
Elisabeth S. Vrba, George H. Denton, Timothy C. Partridge,
Lloyd H. Burckle (editors), Paleoclimate
and Evolution, with Emphasis on Human Origins (Yale University
C. Porter, “Snowline depression in the tropics during the last
glaciation,” Quaternary Science Reviews 20(10):1067-1091
(2000). Assuming a
full-glacial temperature lapse rate of -6°C/1000m,
depression of mean annual temperature in glaciated alpine areas was ca
5.4±0.8°C; it is similar to values of temperature
depression (5-6.4°C) for the last glaciation obtained from
various terrestrial sites, but contrasts with tropical sea-surface
temperature estimates that are only 1-3°C cooler than
of ice sheet formation: C.
H. Haug, R. Tiedemann, “Effect of the formation of the Isthmus of
Atlantic Ocean thermohaline circulation,” Nature 393
(6686):673-676 (18 June 1998).
K. Billups, A. C.
Ravelo, J. C. Zachos, “Early Pliocene deep water circulation in the
western equatorial Atlantic: Implications for high-latitude climate
change,” Paleooceanography 13: (1) 84-95 (February 1998).
C. Johnson, C. A. Sholtz, M. R. Talbot, K. Kelts, R. D. Ricketts, G.
Ngobi, K. Beuning, I. Ssemmanda, J. W. McGill, “Last Plesitocene
desiccation of Lake Victoria and rapid evolution of Cichlid fishes,”
Science 273:1091-1093 (1996).
(1995), pp. 219-220. Richard
Potts, quoted in Nature Science Update (10 May 2001).
Almeda, “Baobabs: gnarled upside-down giants,” Pacific
Discovery (Spring 1997), at http://www.calacademy.org/calwild/pacdis/issues/spring97/wild.htm.
Mark Twain (Samuel Langhorne Clemens), Life on the
Eiseley, The Night Country (Scribners 1971), p.162.
C. Walter, Richard T. Buffler, J. Henrich Bruggemann, Mireille M. M.
Guillaume, Seife M. Berhe, Berhane Negassi, Yoseph Libsekal, Hai
Cheng, R. Lawrence Edwards, Rudo Von Cosel, Didier Néraudeau &
Mario Gagnon, “Early human occupation of the Red Sea coast of
Eritrea during the last interglacial,” Nature 405(6782)65-69
(4 May 2000). And see
Chris Stringer’s comments in the same issue for shorelines more
generally, together with Klein (1999), p.454.
aquatic ape hypothesis (I now prefer to talk of the “shoreline
foraging hypothesis” to avoid the connotation of fully aquatic) and
the associated physiological agenda were reviewed at Mile 136 of my The
River That Flows Uphill (Macmillan 1986), available at http://WilliamCalvin.com/bk3/bk3day9.htm.
Physical anthropologists are unbelievably vehement in their rejection
of any aquatic aspect; they talk of only “fringe groups” believing
it with about the tone they otherwise reserve for those audience
questions about humans evolving from space travelers, so it is not
surprising that their research students stay away from the subject.
Phillip V. Tobias, “Water and human evolution,” Out
There 35: 38-44 (1998) at http://archive.outthere.co.za/98/dec98/disp1dec.html
analyzes the savannah hypothesis and why it proved flawed, emphasizing
the unanswered questions about water.
For a neurobiological agenda that is also usually missing, see
the brain developmental trajectories in Terry Deacon’s The
Symbolic Species (W.
W. Norton 1997).
an excellent example of how predation changes the rates of somatic
growth and reproductive maturity (and makes bodies much larger and
longer-lasting), see Todd A. Crowl and Alan P. Covich,
“Predator-induced life-history shifts in a freshwater snail,” Science
247:949-951 (23 February 1990). For
a survey of dwarf species on the Mediterranean islands, see Paul
Sondaar, “The island sweepstakes,” Natural History
95(9):50-57 (September 1986).
During the last interglacial about 128,000 years ago, a range
of hills in western Normandy was isolated by rising sea level,
becoming the island of Jersey. And
within a time span of only 6,000 years (during which mainland deer
didn’t change – and hadn’t for the previous 400,000 years,
either), the body size of the deer inhabiting the island dropped to
about one-sixth of their original size:
A. M. Lister, “Rapid dwarfing of red deer on Jersey in the
last interglacial,” Nature 342:539-542 (30 November 1989).
Tutu, quoted in “A Tutu tribute,” South African Airways
magazine (November 2000), p.30.
D. Hamilton, “The genetical evolution of social behavior,” Journal
of Theoretical Biology 7:1-52 (1964).
Robert Trivers, “The evolution of reciprocal altruism,” Quarterly
Review of Biology 46:35-57 (1971).
Elliott Sober, David Sloan Wilson, Unto Others: The
Evolution and Psychology of Unselfish Behavior (Harvard University
Peter J. Richerson & Robert Boyd, “The
Pleistocene and the origins of human culture: Built for speed,” In Perspectives in Ethology, Volume 13.
Nicholas S. Thompson and Francois Tonneau, eds. (Kluwer
Academic/Plenum Publishers, New York. 2000), pp. 1-45.
Isaac, as quoted by Leakey & Lewin (1992), p. 181.
fauna associated with Australopithecine fossils indicate a wooded
environment (Reed 1997, p.318); their Paranthropus successors
were sometimes found in wetland environments, but it is only the later
Homo species (ergaster, erectus) that are found in
extremely arid and open landscape.
et al (2000). The
upwelling is from a depth of about 200 m, forming filaments of cold
nutrient-rich waters that extend well offshore and mix with
low-productivity oceanic water, forming a zone of year-round high
The figure is adapted from N. J. Shackleton, “New data on the
evolution of Pliocene climatic variability,” in E. S. Vrba, G. H.
Denton, T. C. Partridge, and L. H. Burckle (eds.), Paleoclimate and
Evolution, With Emphasis on Human Origins (Yale University Press
1995), pp. 242-248.
Walker and Pat Shipman, The
Wisdom of the Bones (Knopf 1996), pp.89-93.
K. Kuman and R. J. Clarke, Sterkfontein Caves: A summary of
scientific research, a pamphlet available at http://cyberfair.gsn.org/adelaar/sterkfon.htm.
Sterkfontein is also
nicely described by Walker and Shipman (1996), p.95.
For the World Heritage Site, see http://www.cradleofhumankind.co.za.
The Taung endocast showing the brain surface is a natural one,
made by concretelike sediments collecting on the inside of the skull
long after death and settling into whatever grooves the brain surface
and blood vessels had imprinted on the inside of the skull.
Latex endocasts can also be made of skulls.
For a photo gallery of skulls and endocasts, see Dean Falk’s
collection at http://www.albany.edu/braindance/gallery.htm.
A comparative collection of brains is at http://brainmuseum.org.
The photograph of Tobias and Calvin is thanks to Dr. Qian Wang.
J. Clarke, Phillip V. Tobias, “Sterkfontein Member 2 foot bones of
the oldest South African hominid,” Science 269:521-524 (28
July 1995). And see http://cyberfair.gsn.org/adelaar/little.htm.
Ronald J. Clarke, “First ever discovery of a well-preserved
skull and associated skeleton of Australopithecus,” South
African Journal of Science 94:460-464 (October 1998) at http://www.nrf.ac.za/sajs/sp_oct98.stm
Ronald J. Clarke, “Discovery of the complete arm and hand of
the 3.3 million-year-old Australopithecus skeleton from
Sterkfontein,” South African Journal of Science 95:477-480
(November/December 1999) at http://www.nrf.ac.za/sajs/sp_nov99.stm
Growth curves in culture, see
Christophe Boesch, Michael Tomasello, “Chimpanzee and human
cultures,” Current Anthropology 39:591-614 (December 1998).
They introduce an unfortunate terminology for growth curve,
calling it the “ratchet effect” when what they mean has no
necessary aspect of backsliding prevention, only of accretion and
William C. McGrew, “The nature of culture:
Prospects and pitfalls of cultural primatology,” Tree
of Origin: What Primate Behavior Can Tell Us about Human Social Evolution, edited by Frans B. M. de Waal
(Harvard University Press 2001), pp.231-254.
Henrique Teotónio, Michael R. Rose,
“Variation in the reversibility of evolution,” Nature
408:463-466 (23 November 2000).
cultural losses: see
Diamond (1997), pp.312-313.
W. Wrangham, “Out of the Pan, into the fire: How our ancestors’ evolution depended on what they ate,”
of Origin: What Primate Behavior Can Tell Us about Human Social Evolution,
edited by Frans B. M. de Waal (Harvard University Press 2001),
Craig B. Stanford, “The ape’s gift:
Meat-eating, meat-sharing, and human evolution,” in Tree
of Origin: What Primate Behavior Can Tell Us about Human Social Evolution,
edited by Frans B. M. de Waal (Harvard University Press 2001),
Alfred Russel Wallace, The
Malay Archipelago: The Land of
the Orang-utan and the Bird of Paradise; A Narrative of Travel With
Studies of Man and Nature (Macmillan
African Museum web page (http://www.museums.org.za/sam/resource/arch/past.htm):
“Tidal Fish Traps: fish traps are artificial tidal pools
constructed of boulders across gullies in the intertidal zone of rocky
shores. In the recent
past some were rebuilt and used by local landowners.
A number were destroyed during the construction of tidal
swimming pools. They may
date back some 1600 to 2000 years when the first pastoralists reached
the western Cape.”
caves, see Klein (1999), p. 456.
China Ruled the Seas: The Treasure Fleet of the Dragon Throne,
University Press 1994). For
more, see http://www.cronab.demon.co.uk/china.htm.
Germs, and Steel: The Fates of Human Societies
Tattersall (1995), p. 231, for a rationale for even more hominid
species and genera.
An excellent starting-point for savanna reading is Peter
Tree Where Man Was Born (E. P. Dutton 1972).
lost their “breeding season” some time ago with the advent of
“concealed” ovulation (the loss of estrus behaviors which
advertise optimal fertility), but similar “analog” changes are
likely in many other areas capable of yielding reproductive isolation.
Tattersall (1998), p.103.
a discussion of imprinting and its role in speciation, see P.B. Vrana,
J.A. Fossella, P. Matteson, T. del Rio, M.J.O. O’Neill, S.M. Tilgham,
“Genetic and epigenetic incompatibilities underlie hybrid dysgenesis
in Peromyscus,” Nature Genetics 25:120-125 (2000).
studies estimate the number of unsuspected pregnancies which abort
early at 13-31 percent, though in some groups (such as women who have
had pelvic inflammatory disease), “early pregnancy loss” can rise
to 70 percent. So far, it
seems to be the conceptions with normal karyotype whose abortion rate
is increased; this isn’t just the obviously abnormal ones (trisomies,
Five cups of coffee per day doubles the spontaneous abortion
rate; see Sven Cnattingius et al., “Caffeine intake and the risk of
first-trimester spontaneous abortion,” New England Journal of
Medicine 343(25):1839-1845 (December 21, 2000). Five-fold increases in spontaneous abortion are seen in some
California counties if women drink the tap water rather than bottled
water; see S. H. Swan et al., “A prospective study of spontaneous
abortion: relation to amount and source of drinking water consumed in
early pregnancy,” Epidemiology 9(2):126-133 (March 1998).
There are now a number of studies about tobacco and alcohol
increasing spontaneous abortions but one must be careful to
distinguish studies whose patient population has a confirmed pregnancy
(seven weeks after last menses) from those “early pregnancy loss”
studies using daily urine samples tested for human chorionic
gonadotropin (hCG) to detect pregnancy via hCG rise in the second week
after ovulation. It is
the abortion rate in the first six weeks which is so high and
unexpected, a rate comparable to the induced abortion rate in many
the hyrax cooperation story, see Walker and Shipman (1996),
D2 dopamine allele story is Kenneth Blum, John G. Cull, Eric R.
Braverman and David E. Comings, “Reward deficiency syndrome,” American
Scientist 84(2): 132ff (March-April 1996) at http://www.sigmaxi.org/amsci/Articles/96Articles/Blum-full.html.
Richard Dawkins, Climbing
Mount Improbable (W.
W. Norton, 1996), p.326.
A readable introduction to hominid tool use is Stanley H.
Ambrose, “Paleolithic Technology and Human Evolution,” Science
291(5509)1748-1753 (2 March 2001).
Ll. Isaac, assisted by Barbara Isaac, Olorgesailie: Archaeological
Studies of a Middle Pleistocene Lake Basin in Kenya (University of
Chicago Press 1977). And
see The Archaeology of Human Origins: Papers by Glynn Isaac,
Barbara Isaac (editor), pp. 289-311 (Cambridge University Press 1989).
Richard Potts, Anna K. Behrensmeyer, Peter Ditchfield,
“Paleolandscape variation and Early Pleistocene hominid activities:
Members 1 and 7, Olorgesailie Formation, Kenya,” Journal of Human
Evolution 37:747-788 (1999).
I first saw a video of this torsional fracture technique for
extracting the whitish-pink bone marrow from a fresh kill, I finally
understood why the Latin prefix myelo- was used for both bone
marrow and for the spinal cord. They
look alike: long, pink tubes. Well,
the fresh spinal cord has a lot of little cut nerves, once you’ve
extracted it, but the resemblance to fresh bone marrow is quite
of contaminated meat (rather than the bone marrow and amputated legs
of my examples) is perhaps best left to animals with specialized guts;
see Ragir et al (2000).
by C. O. Waterhouse are adapted from p.70 of Kenneth P. Oakley’s Man
the Tool-maker (University of Chicago Press 1949).
The somewhat rounder Acheulian handaxe is from St. Acheul, near
Amiens in the Somme. The
more elongate Acheulian handaxe is from Olorgesailie.
“factory site” interpretations:
density of handaxes is not what they would have looked like in any one
year, long ago. The hard
surface on which they rest was what didn’t erode, when rains washed
away the mud from layers above. So
handaxes from many now-missing layers dropped their handaxes down onto
the surfaces which survived the erosion (losing, of course, any
vertical orientation they might have had from landing on edge).
Still, that’s a lot of lost handaxes – and this deflational
surface is likely what was seen by visiting Homo erectus at
various times: an
impressive display of objets trouvé.
Rift Valley diagram is modeled after one in the National Museums of
Science cover photo by R. Potts and W. Huang, showing
opposing sides of a bifacially flaked large cutting tool (~803,000
years old) from the Bose Basin, South China:
Hou Yamei, Richard Potts, Yuan Baoyin, Guo Zhengtang, Alan
Deino, Wang Wei, Jennifer Clark, Xie Guangmao, Huang Weiwen,
“Mid-Pleistocene Acheulean-like stone technology of the Bose Basin,
South China,” Science 287(5458):1622-1626 (3 March 2000).
Isaac, “Throwing and human evolution,” The African
Archaeological Review 5:3-17 (1987).
G. Wynn, “Handaxe enigmas,” World Archaeology 27:10-23
Kathy D. Schick, Nicholas Toth, Making Silent Stones Speak:
Human Evolution and the Dawn of Technology (Simon &
M. O'Brien, “The projectile capabilities of an Acheulian handaxe
Olorgesailie,” Current Anthropology 22:76-79 (1981).
And “What was the Acheulean hand ax?” Natural History
93:20-23 (1984). The
original idea about the handaxe being thrown may be M. D. W. Jeffreys,
“The hand bolt,” Man 65:154 (1965).
Handaxes in dried-up ponds and watercourses:
Isaac (1977); F. Clark Howell, “Isimila: A Paleolithic site
in Africa,” Scientific American 205:118-129 (1961); M. R.
Kleindienst and C. M. Keller, “Towards a functional analysis of
handaxes and cleavers: The evidence from East Africa,” Man
Hunting per se: Matt Cartmill, A View to a Death in the Morning
(Harvard University Press 1993).
H. Calvin, “The unitary hypothesis:
A common neural circuitry for novel manipulations, language,
plan-ahead, and throwing?” pp. 230-250 in Tools, Language, and
Cognition in Human Evolution, edited by Kathleen R. Gibson and Tim
Ingold (Cambridge University Press 1993) at
is one report of chimps throwing with a predatory result, see Frans X.
Plooij, “Tool-use during chimpanzee's bushpig hunt,” Carnivore
H. Calvin, “Rediscovery and the cognitive aspects of toolmaking:
Lessons from the handaxe
,” short commentary at http://faculty.washington.edu/wcalvin/2001/handaxe.htm
introductions to climate and human evolution include Potts (1996);
Stanley (1996); Reed (1997); and Stanley H. Ambrose, “Late
Pleistocene human population bottlenecks, volcanic winter, and
differentiation of modern humans,” Journal of Human Evolution
34(6):623-651 (1998). For
Africa more generally, see John Reader, Africa:
A biography of a continent (Knopf 1998).
that’s why I like acacias so much, having studied cortical neurons
for so long. Besides the
branching pattern similarities, they both have thorns (“dendritic
“pyramidal neuron” is another misnomer (they only look triangular
if their branching dendrites are invisible, as they usually were a
century ago with the early microscopic techniques).
Senut, Martin Pickford, D. Gommery, P. Mein, C. Cheboi, and Yves
Coppens, “First hominid
from the Miocene (Lukeino formation, Kenya),” C. R. Acad. Sci.,
Paris 332, 137-144 (2001), at http://www.becominghuman.org/news_views/article_assets/CRAS-1.PDF.
Verschuren, Kathleen R. Laird, Brian F. Cumming, “Rainfall and
equatorial East Africa during the past 1,100 years,” Nature
403:410-414 (27 January 2000).
times,” see J. B. Webster, in Chronology, Migration and
Drought in Interlacustrine Africa (J. B. Webster, editor), pp.
1-37 (Longman & Dalhousie University Press 1979).
Bond, W. Showers, M. Cheseby, R. Lotti, P. Almasi, P. deMenocal,
P. Priore, H. Cullen, I. Hajdas, G. Bonani, “A pervasive
millennial-scale cycle in North Atlantic Holocene and glacial
cycles,” Science 278:1257-1266 (1997).
Droughts: Peter B.
deMenocal, “Cultural responses to climate change during the late
Holocene,” Science 292:667-673 (27 April 2001).
U. S. map at http://www.sciencemag.org/cgi/content/full/292/5517/667/F1.
The story of the Dust Bowl drought
John Steinbeck, The
Grapes of Wrath (Viking 1939), p.2.
H. Ambrose, “Chronology of the Later Stone Age and Food Production
in East Africa ,” Journal of Archaeological Research
25(4):377-392 (1 April 1998). “Enkapune
Ya Muto rockshelter… contains the oldest known archaeological
horizons spanning this transition [to the Later Stone Age].
Radiocarbon and obsidian hydration dates from this 5-6 m deep cultural
sequence show that the Later Stone Age began substantially earlier
than 46,000 years ago.”
A. Roig, Carlos Le-Quesne, José A. Boninsegna, Keith R. Briffa,
Antonio Lara, Håkan Grudd, Philip D. Jones & Carolina Villagrán,
“Climate variability 50,000 years ago in mid-latitude Chile as
reconstructed from tree rings,” Nature 410(6828): 567-570 (29
March 2001), at http://www.nature.com/nlink/v410/n6828/abs/410567a0_fs.html.
is adapted from a manuscript by my colleague John Michael Wallace,
“Role of the atmosphere in abrupt climate change,” at http://www.geophys.washington.edu.
P. Severinghaus and Edward J. Brook, “An overview of the precise
timing of atmospheric methane change relative to abrupt Greenland
climate events in the past 60 ky,” American Geophysical Union fall
pumping along Silk Road route to China:
Adam Chou, “Migration of early hominids during the
Pleistocene,” Journal of Human Evolution 40(3):A5 (March
Greenland colony: John
Gribbin, Mary Gribbin, Children of the Ice (Basil Blackwell
For group selection, see Sober & Wilson (1998), the special
issue of American Naturalist edited by David Sloan Wilson, or
his short piece, “Human groups as units of selection,” Science
276:1816-1817 (20 June 1997) at http://www.sciencemag.org/cgi/content/full/276/5320/1816.
& Darlington (1995).
William H. Calvin, “The emergence of intelligence,” Scientific
American 271(4):100-107 (October 1994; also appears in Life in
the Universe, 1995), at http://WilliamCalvin.com/1990s/1994SciAmer.htm.
William H. Calvin, “A stone's
throw and its launch window: Timing precision and its
H. Calvin and Derek Bickerton, Lingua ex Machina: Reconciling
Darwin and Chomsky with the Human Brain (MIT Press 2000), at http://WilliamCalvin.com/LEM.
Humphrey's book The Inner Eye (Faber and Faber 1986) is a good
exposition on the role of social life in shaping up intelligence.
de Waal, Good
Natured: The Origins of
Right and Wrong (Harvard University Press 1996), p.146.
James C. Woodburn, “An introduction to Hadza ecology,” in Man
the Hunter, edited by
Matthiessen, The Tree Where Man Was Born (E. P. Dutton 1972),
175 Science literacy, see the National Science Foundation’s report, "Science & Engineering Indicators 1998" , chapter 7, at http://www.nsf.gov/sbe/srs/seind98/pdf/c7.pdf.
Theodosius Dobzhansky outlined the importance of evolution
in the teaching of biology in an issue of The American Biology
Teacher: “Seen in the light of evolution, biology is, perhaps,
intellectually the most satisfying and inspiring science.
Without that light it becomes a pile of sundry facts, some of
them interesting or curious but making no meaningful picture as a
V. Tobias, “Water and human evolution,” Out There 35: 38-44
(1998) at http://archive.outthere.co.za/98/dec98/disp1dec.html
E. Cerling, “Development of grasslands and savannahs in East Africa
during the Neogene,” Paleogeography, Paleoclimatology,
Paleoecology 97:241-247 (1992).
M.J. Wooller, F.A. Street-Perrott, A.D.Q. Agnew, “Late
grassland palaeoecology of Mount Kenya, East Africa: evidence from
charred grass cuticles in lake sediments,” Palaeogeography,
Palaeoclimatology, Palaeoecology 164:223-246 (December 2000).
Documenting ancient fires
like finding evidence for human use of fire
, more difficult than it
first appears. Winds
blow, worms churn, habitation sites erode from foot traffic – all
serve to mix annual layers in any core except an ice or tree core.
When the diffusion process is regular, in the manner of heat
within an ice sheet, deconvolution techniques can sometimes recover
the original depth profile, as has been done for borehole temperatures
in ice. But even if protected pockets of sediment could be found with
the potential for high temporal resolution, the issue is really such
evidence on a continental scale.
Habitats are always being asynchronously disrupted by fire.
The issue for present purposes is how extensive and
simultaneous a fire episode is, for which we must presently rely on
the widespread and quasi-synchronous warm-and-wet and cool-and-dry
from Donald F. Hoffmeister, Mammals of the Grand Canyon
(University of Illinois Press 1971).
K. Kuhl, S. Kirtani, T. Deguchi, A. Hayashi, E. B. Stevens, C. D.
Dugger, and P. Iverson, “Effects of language experience on speech
perception: American and Japanese infants’ perception of /ra/ and
/la/,” Journal of the Acoustical Society of America 102:3135
Sabater-Pi, J. J. Véa, J. Serrallonga, “Did the first hominids
build nests?” Current Anthropology 38(5):914-916 (1997).
Amazon flow in Younger Dryas:
Mark A. Maslin and Stephen J. Burns, “Reconstruction of the
Amazon Basin effective moisture availability over the past 14,000
years,” Science 290: 2285-2287 (22 December 2000).
McBrearty and Alison S. Brooks, “The revolution that wasn't:
A new interpretation of the origin of modern human behavior,”
Journal of Human
Evolution 39 (5):453-563 (November 2000), at p.492.
& Lewin (1992), p.212.
Bickerton, Language and Species (University of Chicago Press
(1995), p.93, and Michael Balter, “New light on the oldest
news article, 283(5404): 920-922 (12 February 1999).
Ian Tattersall, “The origin of the human capacity,” 68th
James Arthur Lecture on the Evolution of the Human Brain, American
Museum of Natural History (1998), at
see John Bargh’s work at http://www.psych.nyu.edu/people/faculty/bargh/.
McBrearty & Brooks (2000).
Ganglike attacks by male chimpanzees on isolated neighbors, see
Wrangham & Peterson (1996).
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 (20 June 2000).
Max Ingman, Henrik Kaessmann,
Svante Pääbo, Ulf Gyllensten, “Mitochondrial genome variation and
the origin of modern humans.” Nature 408:708-713 (7 December
Ornella Semino, Giuseppe
Passarino, Peter J. Oefner, Alice A. Lin, Svetlana Arbuzova, Lars E.
Beckman, Giovanna De Benedictis, Paolo Francalacci, Anastasia Kouvatsi,
Svetlana Limborska, Mladen Marcikia, Anna Mika, Barbara Mika, Dragan
Primorac, A. Silvana Santachiara-Benerecetti, L. Luca Cavalli-Sforza,
and Peter A. Underhill, “The genetic legacy of paleolithic Homo
sapiens sapiens in extant Europeans:
a Y chromosome perspective,” Science 290:1155-1159 (10
David Pilbeam, “Hominoid
systematics: The soft evidence,” Proceedings of the National
Academy of Sciences 97(20):10684-10686 (26 September 2000).
Early dates: remember
that recombination can severely skew the binary-branching trees we
construct. Were there
some horizontal gene transfer affecting the Y chromosome or the mtDNA,
it would make groups that didn’t participate look like they were the
root of the tree.
suddenness, see references on page 330
D. Agenbroad, “New World mammoth distribution,” chapter 3 of Paul
S. Martin, Richard G. Klein, editors, Quaternary Extinctions
(University of Arizona Press 1984), pp. 90-108.
D. Dillehay, “The late Pleistocene cultures of South America,” Evolutionary
Anthropology 7:206-216 (1999).
skull shapes at 10,000 years ago in South America: Walter A. Neves, M.
Blum, A. Prous, J. Powell, “Paleoindian skeletal remains from
Santana do Riacho I, Minas Gerais, Brazil:
Archaeological background, chronological context and
comparative cranial morphology,” American Journal of Physical
Anthropology 114(S32):112-113 (2001).
Fagan (2000), p.214. Another
readable account of the Little Ice Age is Thomas Levenson, Ice Times (Harper & Row
1989), chapter 4.
see Jacques Barzun, From Dawn to Decadence (HarperCollins
witches, see Fagan (2000), p.91.
Johann Wolfgang von Goethe, Maxims and Reflections I.
Carl Sagan, The Demon-haunted World (Random House 1996),
My sketch of the Gulf Stream
the underlying return current (the North Atlantic Deep Water) is
adapted from that of Stefan Rahmstorf, “Risk of sea-change in the
Atlantic,” Nature 388:825-826 (28 August 1997).
are two fine popular treatments of climate change from the 1980s that
contain much useful background for today’s general reader:
John Imbrie and Katherine P. Imbrie, Ice
University Press 1986).
Thomas Levenson, Ice Times:
Climate, Science, and Life on Earth (Harper & Row
The beginning of the ice age at 2.5 million years is dated by
N. J. Shackleton, J. Backman,
Zimmerman, D. V. Kent, M. A. Hall, D. G. Roberts, D. Schnitker, J. G.
Baldauf, A. Desprairies,
Homrighausen, P. Huddlestun, J. B. Keene, A. J. Kaltenback, K. A. O.
Krumsiek, A. C. Morton, J. W. Murray, and J. Westberg-Smith, “Oxygen
isotope calibration of the onset of ice-rafting and history of
glaciation in the North Atlantic region.” Nature 307:620-623
(1984). But, as would be expected from their origins in the earth's
orbital cycles, the Milankovitch rhythms were present long before
that, and can be seen as cycles of deep-sea anoxia: T. D. Herbert and
A. G. Fischer, “Milankovitch climatic origin of mid-Cretaceous black
shale rhythms in central Italy.” Nature 321:739-743 (1986).
The precession and tilt (though not eccentricity) rhythms were faster,
back when the moon's orbit was closer to earth: Andre Berger, M. F.
Loutre, and V. Dehant, “Pre-Quaternary Milankovitch frequencies.” Nature
A number of candidates for a biblical deluge have since
appeared, such as the waterfall when the Mediterranean poured into the
Black Sea, which 7,500 years ago was a freshwater lake.
Few of the shoreline residents of the Black Sea knew anything
more than that the shoreline kept moving inland, at speeds like those
of a glacier surging. See
Fagan (1999), pp. 87-88.
Darwin, “Notes on the effects produced by the ancient glaciers of
Caernarvonshire, and on the boulders transported by floating ice,” Philosophical
Magazine, vol. XXI (1842). For
a chronology of discoveries about the ice ages, see Imbrie &
Imbrie (1986), pp.195-202.
Adhémar history from Wallace S. Broecker and George H. Denton,
“What drives glacial cycles?”, Scientific American
262(1):48-56 (January 1990), at p. 49.
Philander (1998), pp.173-174, has one of the best explanations
of the Milankovitch “orbital” factors that I have seen.
Figures adapted from Andre Berger, M. F. Loutre, H. Gallée,
“Sensitivity of the LLN climate model to the astronomical and CO2
forcings over the last 200 ky,” Climate Dynamics 14:615-629
Peter U. Clark, Richard B. Alley, and David Pollard,
“Northern Hemisphere ice-sheet influences on global climate
change,” Science 286: 1104-1111 (5 November 1999).
(2000), p.98. Note
that I am sidestepping the 100,000 year problem; the astronomy
doesn’t predict a major meltoff at such intervals, and there is much
speculation about exotic and terrestrial causes.
See, for example, Richard A. Muller, “Glacial cycles and
orbital inclination,” Lawrence Berkeley Laboratory Report
LBL-35665 (1994), available at http://www-physics.lbl.gov/www/astro/nemesis/LBL-35665.html.
resonance is another possibility.
of Younger Dryas: Dorothy
Peteet, “Sensitivity and rapidity of vegetational response to
abrupt climate change,” Proceedings of the National Academy of
Sciences (U.S.) 97(4):1359-1361 (15 February 2000) at http://www.pnas.org/cgi/content/full/97/4/1359
The temperature and precipitation records are
replotted from the data of K. M. Cuffey and G. D. Clow,
“Temperature, accumulation, and ice sheet elevation in Central
Greenland through the last deglacial transition,” Journal of
Geophysical Research 102(C12):26383-96 (1997).
well-written account of Hans Oeschger ‘s study of fluctuations seen
in the ice cores can be found in Thomas Levenson, Ice Times
(Harper & Row 1989), chapter 3.
Thomas Stocker’s obit of Oeschger can be found at http://www.climate.unibe.ch/oeschger/obituary.html.
Heinrich events demonstrate that the North Atlantic may have a third
mode of ocean circulation. Today,
and in the warm part of the D-O cycles, there is both far-north (above
60°N) and near-north sinking. During
the cool-and-dry part of the D-O cycle, the far-north sinking shuts
down. But during the
Heinrich events, with so much fresh water being released as icebergs
sail toward the Bay of Biscay, even the near-north sinking process
shuts down, leaving warm water pooling in the southern oceans with no
place to go. See Alley
M. Cuffey and Shawn J. Marshall, “Substantial contribution to
sea-level rise during the last interglacial from the Greenland ice
sheet,” Nature 404:591-594 (2000).
The West Antarctic ice sheet contains enough water to raise sea
level about 6 meters, as does Greenland; the East Antarctic ice sheet
is huge in comparison, containing enough to raise sea level 60 meters.
All other glaciers in the world combined contain about 0.5
meters worth. Both
Greenland and West Antarctica have sunk enough under the weight of
their ice that much of the ground beneath them is now below sea level,
making them particularly vulnerable.
S. Broecker, D. Peteet, I. Hajdas, J. Lin, E. Clark, “Antiphasing
between rainfall in Africa's Rift Valley and North America's Great
Basin,” Quaternary Research 50:12-20 (1998).
“The beginning of the Bølling-Alleröd warm period was
marked in Greenland by an abrupt rise in 18O, an abrupt
drop in dust rain, and an abrupt increase in atmospheric methane
content. The surface
waters in the Norwegian Sea underwent a simultaneous abrupt warming.
At about this time, a major change in the pattern of global
rainfall occurred. Lake Victoria (latitude 0°), which prior to this time was
dry, was rejuvenated. The
Red Sea, which prior to this time was hypersaline, freshened.”
My sketch of the extent of grounded northern ice sheets is
shown atop a satellite photo at modern sea levels with floating sea
ice removed. The sketch
is adapted from the one in Clark et al. (1999).
resolution on the scale of a year or two can be obtained from
semi-fossil trees, e.g., Roig et al (2001) have a 1229-year-long
stretch of tree-ring widths from the middle of the last ice age at 40°S
that shows abrupt droughts with abrupt recoveries (tenfold changes in
yearly accumulation), but they are floating in absolute time and such
local records cannot yet be matched to events in the ice-core records.
Tropics affected: Konrad
A. Hughen, Jonathan T. Overpeck, Scott J. Lehman, Michaele Kashgarian,
John Southon, Larry C. Peterson, Richard Alley, & Daniel M. Sigman,
“Deglacial changes in ocean circulation from an extended radiocarbon
calibration,” Nature 391:65-68 (1 January 1998).
The figure is adapted from their figure 2 (GISP2 accumulation
record and Cariaco gray scale). And
see the Cariaco Project at http://paria.marine.usf.edu/cariaco/.
J. P. Kennett and B. L. Ingram, “A 20,000 year record of
ocean circulation and climate change from the Santa Barbara Basin,” Nature
377: 510-517 (1995).
Climate change was synchronous (within a few decades) over a
region of at least hemispheric extent when rewarming from the Younger
Dryas: Jeffrey P.
Severinghaus, Todd Sowers, Edward J. Brook, Richard B. Alley, &
Michael L. Bender, “Timing of abrupt climate change at the end of
the Younger Dryas interval from thermally fractionated gases in polar
391:141-146 (8 January 1998).
A. Eddy and Hans Oeschger, editors, Global
Changes in the Perspective of the Past (Wiley 1993).
“Broecker, too, heard Oeschger that year”:
see Wallace S. Broecker, “Will our ride into the greenhouse
future be a smooth one?” GSA Today 7(5):1-7 (May 1997). For more autobiography, see his “Converging paths leading
to the role of oceans in climate change,” Annual Reviews of
Energy and Environment 25:1-19 (2000).
see Fagan (1999), p.87.
stability” means avoiding the centuries-duration scale of D-O events
of 5-15°C, though that leaves a lot of room for more minor
fluctuations such as the 1,500-year cycle and the decade-scale rhythms
that are now being studied. For some contrasts between the
Younger Dryas and the most serious droughts since then at 8200, 5200,
and 4200 years ago, see Fagan (1999) and Harvey Weiss,
“Beyond the Younger Dryas:
Collapse as adaptation to abrupt climate change in ancient West
Asia and the Eastern Mediterranean,” pp. 75-98 in Confronting
Natural Disaster: Engaging the Past to Understand the Future, G.
Bawden and R. Reycraft, editors (University of New Mexico Press 2000),
E. Raymo, K. Ganley, S. Carter, D. W. Oppo, & J. McManus,
“Millennial-scale climate instability during the early Pleistocene
392:699-702 (16 April 1998).
P. E. Biscaye, F. E. Grousset, M. Revel, S. VanderGaast, G. A.
Zielinski, A. Vaars, and G. Kukla, “Asian provenance of glacial dust
(stage2) in the Greenland Ice Sheet Project 2 Ice Core, Summit,
Greenland,” Journal of Geophysical Research 102:765-781
(1997). Carbon dioxide is
best studied in bubbles from Antarctic cores, where the ice is fewer
potential contaminants than ice from Greenland; in general, see Alley
M. Grootes, M. Stuiver, J. W. C. White, S. Johnsen, and J. Jouzel,
“Comparison of oxygen isotope records from the GISP2 and GRIP
Greenland ice cores,” Nature 366:552-554 (1993).
Willi Dansgaard, S. J. Johnsen, H. B. Clausen, D. Dahl-Jensen,
N. S. Gundestrup, C. U. Hammer, C. S. Hvidberg, J. P. Steffensen, A.
E. Sveinbjörnsdottir, J. Jouzel, G. Bond,
“Evidence for general instability of past climate from a 250
kyr ice core,” Nature 364:218-219 (1993).
Figure adapted from J.R. Petit, J. Jouzel, D. Raynaud, N.I.
Barkov, J.-M. Barnola, I. Basile, M. Bender, J. Chappellaz, M. Davis,
G. Delayque, M. Delmotte, V.M. Kotlyakov, M. Legrand, V.Y. Lipenkov,
C. Lorius, L. Pépin, C. Ritz, E. Saltzman, and M. Stievenard,
“Climate and atmospheric history of the past 420,000 years from the
Vostok ice core, Antarctica,” Nature 399:429-436 (1999).
Anderson, “Same time tomorrow” lyrics, Bright
Red, track 14 (Time
Polyak, Margo H. Edwards, Bernard J. Coakley, Martin Jakobsson, “Ice
shelves in the Pleistocene Arctic Ocean inferred from glaciogenic
deep-sea bedforms,” Nature 410:453-457 (22 March 2001).
Bottom scouring at 1000 m depths; icebergs in the Arctic Ocean
have at most 50-m draughts, whereas icebergs off Antarctica and
Greenland reach depths of 550 m.
reason I say “habitable world appears to be chilled” is that some
areas of the South Pacific and Atlantic Oceans, and some (but not all)
parts of Antarctica, may be exceptions.
The extent of the Younger Dryas in higher southern latitudes
may be somewhat spotty, as it is superimposed on the warming trend
after the last glacial maximum which began in the south and spread
north. See K. D. Bennett,
S. G. Haberle, and S. H. Lumley,
“The Last Glacial-Holocene transition in southern Chile,” Science
290:325-328 (13 October 2000), http://www.sciencemag.org/cgi/content/abstract/290/5490/325
and the perspective at pp.285-286.
S. Broecker, “Chaotic climate,” Scientific American
273(5):62-69 (November 1995). A
hundred Amazons is Broecker’s figure; if the Amazon flow is instead
taken as 0.19 Sv, and the southbound NADW off Newfoundland as 13 Sv,
then it is more like 70 Amazons.
But deep water production by convection may be less, depending
on how much NADW is Arctic in origin and how much is simply
recirculated Antarctic bottom water (extremely dense water, formed as
brine under the sea ice around polynas offshore of Antarctica and
sliding down the continental shelf into the depths without much
mixing, creates a giant pool of dense water extending all the way up
the bottom of the Atlantic to about 60°N).
Greenland Sea production is said to be 5.6 Sv, about equally
divided between the sills to the east and west of Iceland.
Labrador Sea production is difficult to estimate because of the
local gyre and the frequent annual failures.
Bindschadler, “Future of the West Antarctic Ice Sheet,” Science
282:428-429 (16 October 1998).
G. H. Denton, C. H. Hendy, “Younger Dryas Age Advance of
Franz Josef Glacier in the Southern Alps of New Zealand,” Science
264:1434-1437 (3 June 1994; follow up at 271:668-669, 2 February
Judith Lean and David Rind,
“Earth's Response to a Variable Sun,” Science 292(5515)
234-236 (13 April 2001).
Peter V. Foukal, “The variable sun,” Scientific American
262(2):34-41 (February 1990).
U. Neff, S. J. Burns, A. Mangini, M. Mudelsee, D. Fleitmann
& A. Matter, “Strong coherence between solar variability and the
monsoon in Oman between 9 and 6 kyr ago,” Nature 411:290-293
J. D. Haigh, “The impact of solar variability on climate,” Science
Reductions in solar output might, of course, be one of the
things that set the stage for an abrupt cooling, as might the North
Atlantic Oscillation and other atmospheric cycles like El Niño.
Causes usually don’t come one at a time, but combine in
For climate variability more generally, start at the CLIVAR web
pages at http://www.clivar.org/start.htm
Alley (2000), p.3.
M. Stommel, “Thermohaline convection with two stable regimes of
flow,” Tellus 13:224-230 (1961) had the concept of freshening
of surface waters interfering with the thermohaline sinking.
The conceptual map is from Stommel (1957), see http://www.aoml.noaa.gov/hrd/Landsea/climtrend/.
S. Broecker, “The great ocean conveyor
Wallace S. Broecker, "Abrupt climate change: causal
constraints provided by the paleoclimate record," Earth-Science
Reviews 51:137-154 (August 2000).
D. J. Webb and N. Suginohara, “Oceanography: Vertical mixing
in the ocean,” Nature 409:37 (4 January 2001).
Munk, Laurence Armi, Kenneth Fischer, F. Zachariasen, “Spirals on
the sea,” Proceedings of the Royal Society: Mathematical,
Physical & Engineering Sciences 456:1217-1280 (1997).
First seen in the Apollo missions of the 1960s, spirals are
broadly distributed over the world's oceans, 10-25 km in size and
Whirlpools associated with salt
play an interesting role in Norse legends.
See chapter 6 of Giorgio de Santillana and Hertha von Dechend, Hamlet’s
Mill: An Essay Investigating the Origins of Human Knowledge and its
Transmission Through Myth (Godine 1969).
Sy, Monika Rhein, John R. N. Lazier, Klaus Peter Koltermann, Jens
Meincke, Alfred Putzka, and Manfred Bersch, “Surprisingly rapid
spreading of newly formed intermediate waters across the North
Atlantic Ocean,” Nature 386:675-679 (17 April 1997).
S. McCartney, Ruth G. Curry, Hugo F. Bezdek, “North Atlantic
transformation pipeline chills and redistributes subtropical water,”
Oceanus 39(2):19-23 (Fall/winter 1996).
This article elaborates on the multi-year aspects of the
formation of salt sinking in the sub-polar gyre.
from Greenland to Labrador domination:
R. Dickson, J. Lazier, J. Meincke, P. Rhines, J. Swift,
“Long-term coordinated changes in the convective activity of the
North Atlantic,” Progress in Oceanography 38:241-295 (1996).
G. C. Bond, R. Lotti, “Iceberg discharges into the North
Atlantic on millennial time scales during the last glaciation,” Science
267:1005 (17 February 1995).
Wallace S. Broecker, “Massive iceberg discharges as triggers
for global climate change,” Nature 372:421-424 (1994).
Date for closure of “Old Panama
Neil D. Opdyke, “Mammalian migration and climate over the
last seven million years,” chapter 8 in Paleoclimate and
Evolution, with Emphasis on Human Origins, edited by Elisabeth S.
Vrba, George H. Denton, Timothy C. Partridge, Lloyd H. Burckle (Yale
University Press 1995), pp.109-114 at p.112.
C. H. Haug, R. Tiedemann, “Effect of the formation of the
Isthmus of Panama
Atlantic Ocean thermohaline circulation,” Nature
393(6686):673-676 (18 June 1998).
There is a similar theory for how African climate was affected
by New Guinea moving northward to close off the easy circulation
between Pacific and Indian Oceans:
Mark A. Cane, Peter Molnar,
“Closing of the Indonesian seaway as a precursor to east
African aridification around 3–4 million years ago,” Nature
411:157-162 (10 May 2001).
Photograph of Greenland mountain peaks exposed by the thinning
continental ice sheet: Rock
protruding through an ice sheet is called a nunatak.
The low light angle is from the midnight sun, as the picture
was taken looking south on an eastbound flight in the summer in the
early morning hours.
Schlosser, Gerhard Bönisch, Monika Rhein, Reinhold Bayer,
“Reduction of deepwater formation in the Greenland Sea during the
1980s: Evidence from
tracer data,” Science 251:1054-1056 (1 March 1991).
Gerhard Bönisch, Johan Blindheim, John L. Bullister, Peter
Schlosser, and Douglas W. R. Wallace, “Long term trends of
temperature, salinity, density,
and transient tracers in the Central Greenland Sea,” Journal of
Geophysical Research 102:18553-18571 (1997), see http://www.ldeo.columbia.edu/~noblegas/gerhard/GIN/tspgs/tsp65.html.
S. McCartney, “North Atlantic Oscillation,” Oceanus
39(2):13 (Fall/winter 1996). The
regional atmospheric circulation over the North Atlantic normally
features a high over the Azores and a low near Greenland and Iceland
– the westerlies are intense but the cold air from Canada is warmed
before reaching Europe. When
the low shifts as far south as Newfoundland, a high develops over
northern Greenland; this brings cold arctic air west from northern
Europe to be warmed by the Norwegian Current and thus warm Greenland
and North America rather than Europe. The Labrador Sea is much less stormy and this likely affects
NAO is best understood as a ring of pressure anomalies extending
around the globe, not just a North Atlantic phenomenon (something
similar happens in the Southern Hemisphere at similar latitudes).
See Dennis L. Hartmann, John M. Wallace, Varavut Limpasuvan,
David W. J. Thompson, and James R. Holton, “Can ozone depletion and
global warming interact to produce rapid climate change?” Proceedings
of the National Academy of Sciences (U.S.) 97:1412-1417 (15
February 2000) at http://www.pnas.org/cgi/content/full/97/4/1319.
The relationships between the NAO and deep water production are
discussed by R. Dickson, “Observations of DecCen climate variability
in convection and water mass formation in the northern hemisphere,”
in the CLIVAR Villefranche workshop summary at
More generally, see the Climate Research Committee, National
Research Council, Natural
Climate Variability on Decade-to-Century Time Scales (National
Academy Press 1995). Excerpts
can be found at http://www.nap.edu/bookstore/isbn/0309054494.html.
Sinking to the very bottom may be important for the return leg
of the trip, south past the coast of Newfoundland where it must stay
beneath the Gulf Stream
There is some speculation that it sometimes doesn’t, and is
swept eastward, illustrating a mechanism for creating blobs that
recirculate. It is known
that semi-salty, or anomalously warm or cool, blobs even travel from
the subtropics, up and around the Greenland Seas and back around to
the Labrador Sea, suggesting another failure mode for late winter
downwelling; see Raymond W. Schmitt, “If rain falls on the ocean,
does it make a sound?” Oceanus 39(2):4-8 (Fall/winter 1996).
Thomas F. Stocker, Olivier Marchal, “Abrupt climate change in
the computer: Is it real?” Proceedings of the National Academy of
Sciences (U.S.) 97:1362-1365 (15 February 2000) at http://www.climate.unibe.ch/~stocker/.
Andrey Ganopolski and Stefan
Rahmstorf, “Simulation of rapid glacial climate changes in a coupled
climate model,” Nature 409:153-158 (11 January 2001) at http://www.pik-potsdam.de/~stefan/.
Hansen, William R. Turrell, Svein Østerhus, “Decreasing overflow
from the Nordic seas into the Atlantic Ocean through the Faroe Bank
channel since 1950,” Nature 411:927-930 (21 June 2001).
For the hinge from which icebergs break off, see E. J. Rignot,
S. P. Gogineni, W. B. Krabill, S. Ekholm, “North and
northeast Greenland ice discharge from satellite radar interferometry,”
Science 276:934-937 (9 May 1997).
Sometimes glaciers surge a mile a
month (the Bering glacier east of Cordova, Alaska – North
America’s longest glacier – is currently surging), but that’s
because of warming, not cooling.
Another one of the ice paradoxes is that glaciers can advance
for either reason. Glaciers,
too, have modes of operation: once
melting starts, a mountain of ice tends to collapse, spreading
meltwater runs off beneath the glacier (and can form there from all
the trapped heat from the earth), it smoothes the undersurface and
greases the skids. The
glacial snout may advance so quickly that the ocean’s chipping away
at it cannot keep up. And
so the snout of the glacier pushes further into the sea over a course
of months. Eventually the
tides may break it loose.
S. Reeburgh, D. L. Nebert, “The birth and death of Russell Lake,” Alaska
Science Forum 832 (3 August 1987) at http://www.gi.alaska.edu/ScienceForum/ASF8/832.html. See also http://www.asf.alaska.edu/daac%5Fdocuments/cdrom%5Fdocs/38079.html
B. Alley, P. A. Mayewski, T. Sowers, K. C. Taylor, and P. U. Clark,
"Holocene climatic instability: A prominent, widespread event
8200 yr ago." Geology 25:483-486 (1997).
D. C. Barber, A. Dyke, C. Hillaire-Marcel, A. E. Jennings, J.
T. Andrews, M. W. Kerwin, G. Bilodeau, R. Mcneely, J. Southon, M. D.
Morehead & J.-M. Gagnon, “Forcing of the cold event of 8,200
years ago by catastrophic drainage of Laurentide lakes,” Nature
A. Kerr, “Warming's unpleasant surprise: Shivering in the
greenhouse?” Science 281:156-158 (news article, 10 July
An even longer record comes from the high tropics, going back
about 500,000 years and showing many abrupt temperature changes.
L. G. Thompson, T. Yao, M. E. Davis, K. A. Henderson, E.
Mosley-Thompson, P.-N. Lin, J. Beer, H.-A. Synal, J. Cole-Dai, J. F.
Bolzan, “Tropical climate instability: The last glacial cycle from a
Qinghai-Tibetan ice core,” Science 276:1821-1825 (20 June
1997) at http://www.sciencemag.org/cgi/content/full/276/5320/1821.
Mark Maslin, “Sultry last interglacial gets a sudden
chill,” Earth in Space 9(7):12-14 (March 1997) at http://www.agu.org/sci_soc/eismaslin.html.
One of the current uncertainties about the mid-Eemian cooling
event at 122,000 years is whether it involved the complete shutdown of
the North Atlantic Deep Water production; various ocean-floor cores
suggest it didn’t.
D. Keigwin, W. B. Curry, S. J. Lehman, S. Johnsen, “The role of the
deep ocean in North Atlantic climate change between 70 and 130 kyr
ago,” Nature 371:323-326 (22 September 1994).
J. F. McManus, G. C. Bond, W. S. Broecker, S. Johnsen, L.
Labeyrie, S. Higgins, “High-resolution climate records from the
North Atlantic during the last interglacial,” Nature
371:326-329 (22 September 1994).
Robert R. Dickson, “The local, regional, and global
significance of exchanges through the Denmark Strait and Irminger
Sea,” in Natural Climate Variability of Decade-to-Century Time
Scales (National Academy Press 1995), pp. 305-317.
R. R. Dickson, J. Meincke, S-A. Malmberg, and A. J. Lee, “The
`great salinity anomaly’ in the northern North Atlantic
1968-1982,” Progress in Oceanography 20:103-151 (1988).
Note that the Great Salinity Anomaly, equivalent to an extra
2,000 km3 of fresh water, is not usually treated as a fjord
flood but as a variant on a semi-salty current out of the Arctic Sea.
This volume is about 500 times the freshwater flux from
Alaska’s Russell Fjord over a five-month period – but then the
reservoir capacity of the east Greenland fjord system at 70-77°N is
also extraordinary and ice dams can span multiple years.
The travel time from the Labrador Sea to Bermuda is about six
to restart: it’s an
example of hysteresis. This
is one of those asymmetric situations where it is easy to get in but
hard to get out, something like a one-way street where you can’t
turn around but are forced to go all the way around the block instead.
See the diagram in Stocker & Marchal (2000).
argument for 1,500-year cycle: Here
I am paraphrasing from a lecture at the University of Washington by
Wally Broecker (12 December 2000), “The big amplifier– bipolar
Note also that desert dust inhibits precipitation by a
mechanism that increases albedo:
Daniel Rosenfeld, Yinon Rudich,, and Ronen Lahav, “Desert
dust suppressing precipitation: A possible desertification feedback
loop,” Proc. Natl. Acad. Sci. USA 98(11):5975-5980 (22 May 2001).
Ray T. Pierrehumbert, “Climate change and the tropical
Pacific: The sleeping dragon wakes,”
Proceedings of the National Academy of Sciences (U.S.)
97:1355-1358 (10 February 2000) at http://www.pnas.org/cgi/content/full/97/4/1355
Levenson, Ice Times (Harper & Row 1989), p.49.
more on why open ocean occurs occasionally in Arctic summers,
sometimes even at the pole itself, see http://psc.apl.washington.edu/northpole/NPOpenWater.html.
There is an enormous heat flux through them, as the difference
between surface and air temperature is 30°C.
They soon refreeze (unless they are maintained open by offshore
winds, as in Antarctica) and produce a layer of brine.
News article by John Noble Wilford, “Ages-old polar icecap is
melting, scientists find,” New York Times (August 19, 2000),
Actually, none of the Arctic sea ice is much over three years
old, and that at 90°N is usually only a year old.
The more common confusion is
between an ice sheet, which can be 3,000 meters thick, and floating
sea ice (in the Arctic, seldom more than 3 meters thick).
The Antarctic is a continent surrounded by ocean; the Arctic is
a nearly landlocked sea surrounded by continents which empty fresh
water into it via north-flowing rivers; using the same word,
“icecap,” for both is misleading, however correct.
D. A. Rothrock, Y. Yu, G. A. Maykut, “Thinning of sea-ice
cover,” Geophysical Research Letters 26:3469-3472 (1 December
Ola M. Johannessen, Elena V. Shalina, Martin W. Miles,
“Satellite evidence for an Arctic sea ice cover in
transformation,” Science 286:1937-1939 (3 December 1999).
Konstantin Y. Vinnikov, Alan Robock, Ronald J. Stouffer, John
E. Walsh, Claire L. Parkinson, Donald J. Cavalieri, John F. B.
Mitchell, Donald Garrett, Victor F. Zakharov, “Global warming and
Northern Hemisphere sea ice extent,” Science 286:1934-1937 (3
December 1999). And see
the follow up at Science
special pleading works much better with real juries, from which
knowledgeable jurors have been systematically excluded, than it does
with the general public. Anyone
who knows more about the science or technology than the lawyers is
usually rejected during jury selection.
And the judges allow it.
Instrumental record: J.
Fred Singer, “Global warming: An insignificant trend?” Science
292:1063 (2001). And see
Donald Kennedy’s pointed reply which follows it.
change from wet to dry in the Sahara
least, as measured by offshore dust) as the axial tilt gradually
changes: Peter B.
deMenocal, J. Ortiz, T. Guilderson, J. Adkins, M. Sarnthein, L. Baker,
and M. Yarusinsky, “Abrupt onset and termination of the African
Humid Period: Rapid
climate responses to gradual insolation forcing,” Quaternary
Science Review 19: 347-361 (2000).
I cannot find any literature on equatorial warming triggering
reorganization for the D-O events, there are reports, for the
glacial-interglacial transition, that Pacific sea surface temperatures
warmed 3,000 years before changes in ice volumes.
See David W. Lea, Dorothy K. Pak, and Howard J. Spero,
“Climate impact of Late Quaternary equatorial Pacific sea
surface,” Science 289:1719 (8 September 2000) at http://www.sciencemag.org/cgi/content/full/289/5485/1719.
Quote from Broecker (1997), p. 5.
Quote from Alley (2000), p. 83.
Philander (1999), p.3.
the comparison of Canada to Europe, Conway Leovy reminds me that
Europe does not have an equivalent of the rain shadow from the
O. Wilson, Consilience: Unity of Knowledge (Knopf 1998),
warming: K. E. Taylor, J. E. Penner, “Response of the climate
system to atmospheric aerosols and greenhouse gases,” Nature
idea of a Precambrian glaciation covering even the tropics goes back
to the 1960s but it was dismissed, despite the evidence of glacial
till in suspicious places, overlain by tropical sediments.
Essentially, should the sun’s output reaching the earth
decline a few percent (Sun itself, dust clouds, whatever), even the
tropics freeze and the albedo keeps it that way.
The idea was revived in the 1990s because of a mechanism
(volcanic CO2 becoming 10% of air) that would melt it back
within a few million years, after which there is a Hothouse Earth for
a few million years until the thirty-fold-greater CO2 is
removed from the atmosphere. At
least two such episodes are thought to have occurred between 750 and
550 million years ago.
Paul F. Hoffman, Alan J. Kaufman, Galen P. Halverson, and
Daniel P. Schrag, “A neoproterozoic snowball earth,” Science
281(5381):1342-1346 (28 August 1998).
Paul F. Hoffman, Daniel P. Schrag, “Snowball Earth,” Scientific
American, pp. 68-75 (January 2000) at http://www.sciam.com/2000/0100issue/0100hoffman.html
feedback, see Alley (2000), p.86.
J. Charlson, James E. Lovelock, Meinrat O. Andreae, Stephen G. Warren,
“Oceanic phytoplankton, atmospheric sulphur, cloud albedo, and
H. Calvin, C. F. Stevens, “A Markoff process model for neuron
behavior in the interspike interval,” Proceedings of the Annual
Conference on Engineering in Medicine and Biology 7:118 (1965).
Thomas, Late Night Thoughts on Listening to Mahler's Ninth
Symphony, (Viking 1983), p. 15.
Burns, The Shape and Form of Puget Sound (University of
Washington Press 1985), p. 43.
Parfit, “Before Noah, there were the Lake Missoula Floods,” Smithsonian
John Eliot Allen and Marjorie Burns, Cataclysms on the
Columbia (Portland: Timber Press 1986).
Antonio Damasio, The Feeling of
What Happens (1999).
“Consciousness and its revelations allow us to create a
better life… but the price we pay for that better life is high. It
is not just the price of risk and danger and pain. It is the price of knowing
risk, danger, and pain. Worse
even: it is the price of knowing what pleasure is and knowing
when it is missing or unattainable.” [p.316]
H. Calvin, “The great climate flip-flop,” The Atlantic Monthly
281(1):47-64 (January 1998) at
underreporting of abrupt climate change persisted from 1985 to 1998,
even in the face of substantial recognition of some of the major
players. For example,
Wallace S. Broecker – easily the most vigorous of the geoscientists
in trying to alert the scientific community, and author of several Scientific
American articles – was awarded the U.S. National Medal of
Science by President Clinton in 1996 for “contributions to
understanding chemical changes in the ocean and atmosphere.”
The Danish ice-core expert Willi Dansgaard and the British
oceanographer Nicholas Shackleton received the Crafoord Prize from the
Swedish Academy in 1995 (see http://www.kva.se/prizes.html).
Dansgaard, the Swiss climatologist Hans Oeschger, and the
French climatologist Claude Lorius received the $150,000 Tyler Prize
despite all this recognition and all those news stories in Science
and Nature, the bistable climate story itself (sudden warmings,
flipping to sudden coolings) was seldom reported in the popular press.
It was conflated with other rapid climate changes (volcanoes,
ice shelves breaking up) lacking bistable states, or it was simply
lost in a greenhouse story. It
would be interesting for some student of the media to sort out the
underlying reasons why such a major story was ignored.
exception was Ross Gelbspan, The
Heat Is On (Addison-Wesley 1997), who treats the abrupt
cooling story at pp. 28-31.
warming” is a classic example of how not to frame an issue.
It hurts no matter what caused it; assigning fault doesn’t
resolve anything in this case. And
just because something is “natural” doesn’t mean it is out of
our control. (Floods? Smallpox?)
Many of the people whose pockets might be hurt by expenses for
combating warming are quite happy to see the issues dumped solely into
the laps of the scientists, perhaps because they know that scientific
studies always raise more questions than they answer, and so the issue
of whether science has spoken on the issue can be indefinitely
postponed. Public policy
has some similarities to medicine; the physician who waits until dead
certain of a diagnosis before starting treatment may often wind up
with a dead patient. Often,
one cannot wait for scientific certainty.
Peter Schuster, “Molecular insights into life and
evolution,” the 1998 Schrödinger lecture, at
Trinity College Dublin, http://www.tcd.ie/Physics/Schrodinger/Lecture4/lecture4.html.
Copyright ©2002 by
William H. Calvin
Book's Table of Contents
All of my books are on the web.
The six out-of-print books
are again available via Authors Guild reprint editions,