Notes
Chapter 1. Following the Gulf Stream to Europe:
Tracking Climate Change and Human Evolution
1994 Update: The current dating of the Younger Dryas onset is 13,000 years
ago rather than the 11,500 mentioned in this 1990 manuscript. And the abrupt
climate changes are even more frequent than then appeared: see Wallace S. Broecker,
"Massive iceberg discharges as triggers for global climate change." Nature
372:421-424 (1 December 1994). For updates on El Nino, see El Nino tuitorial
from NOAA.
2 Robert Ardrey, The Hunting Hypothesis
(Atheneum, 1976).
4 Lionel E. Jackson, Jr. and Alejandra Duk-Rodkin, "Geology of the ice-free corridor." University
of Washington lecture (19 January 1988). E. James
Dixon, "Eastern Beringian paleoindians and the
paleoenvironments of the ice-free corridor."
University of Washington lecture (1 March 1988).
Michael Wendorf, "Diabetes, the ice free corridor,
and the paleoindian settlement of North America."
American Journal of Physical Anthropology
79(4):503-520 (1989). Joseph H. Greenberg,
Christy G. Turner II, and Stephen L. Zegura, "The
settlement of the Americas: A Comparison of the
linguistic, dental, and genetic evidence." Current
Anthropology 27(5):477-497 (1986).
6 For the general anthropological background
concerning ice-age Europe, see John Gowlett,
Ascent to Civilization: The Archaeology of Early
Man (Knopf, 1984). For the general background
on the ice-age theories, see John Imbrie and
Katherine P. Imbrie, Ice Ages
(Harvard University Press, 1986); John Gribbin and
Mary Gribbin, Children of the Ice: Climate and
Human Origins (Basil Blackwell, 1990); and
Wallace S. Broecker and George H. Denton,
"What drives glacial cycles?" Scientific
American 262(1):48-56 (January 1990). For the
greenhouse, see Warren M. Washington, "Where's
the heat?" Natural History (3):66-72 (1990).
7 Initially, several layers of Dryas pollen
showed up in Denmark, but only the more recent of
them was seen elsewhere, hence the "Younger Dryas"
terminology that is conventional for this period. From
a lecture by Dorothy M. Peteet, "Younger Dryas
oscillation: a late-glacial example of abrupt climatic
change," University of Washington (28 February
1989).
The basic data on the cold spikes is in: W.
Dansgaard, H. B. Clausen, N. Gundestrup, C. U.
Hammer, S. F. Johnsen, P. M. Kristinsdottir, and
N. Reeh, "A new Greenland deep ice core."
Science 218:1273-1277 (1982). For droughts,
see F. Alayne Street-Perrott and R. Ross
Perrott, "Abrupt climate fluctuations in the tropics:
the influence of Atlantic Ocean circulation."
Nature 343:607-612 (15 February 1990). For
what droughts did in the U.S. Southwest, see Robert
C. Euler, George J. Gumerman, Thor N. V.
Karlstrom, Jeffrey S. Dean, and Richard H.
Hevly, "The Colorado plateau: Cultural dynamics
and paleoenvironment." Science
205:1089-1101 (14 September 1979).
The timing of the termination of the Dryas at
about 10,700 years ago is in W. Dansgaard, J. W. C.
White, and S. J. Johnsen, "The abrupt termination of
the Younger Dryas climate event." Nature
339:532-534 (15 June 1989).
The basics on the carbon budget of the earth can
be found in Richard A. Houghton and George M.
Woodwell, "Global climatic change." Scientific
American 260(4):36-44 (April 1989).
David A. Peel, "Ice-age clues for warmer world."
Nature 339:508-509 (15 June 1989).
Wallace S. Broecker, Dorothy M. Peteet,
and David Rind, "Does the ocean-atmosphere system
have more than one stable mode of operation."
Nature 315:21-26 (2 May 1985). Wallace
S. Broecker, "Unpleasant surprises in the
greenhouse?" Nature 328:123-126 (9 June
1987). And Broecker et al, "The chronology of the
deglaciation: Implications to the cause of the Younger
Dryas cooling." Paleoceanography 3:1-19
(1988). Richard G. Fairbanks, "A 17,000-year
glacio-eustatic sea level record: Influence of glacial
melting rates on the Younger Dryas event and deep-ocean circulation." Nature 342:637-642
(7 December 1989). E. Jansen and T. Veum,
"Evidence for two-step deglaciation and its impact on
North Atlantic deep-water circulation."
Nature 343:612-616 (15 February 1990).
Hans Oeschger and C. C. Langway, editors, "The
Environmental Record in Glaciers and Ice Sheets."
Dahlem Workshop 8 (Wiley, 1989). Hans
Oeschger and H. U. Dütsch, "Ozone and the
Greenhouse Effect." Nature 339:19 (4 May
1989). Robert J. Charlson, James E. Lovelock,
Meinrat O. Andreae, and Stephen G. Warren,
"Oceanic phytoplankton, atmospheric sulphur, cloud
albedo, and climate." Nature 326:655-661
(1987). And the news stories regarding cloud cover
and albedo, "Pinning down clouds" in Scientific
American 260(5):22-24 (May 1989) and "Cloudy
concerns" in Science News 136:106-110
(12 August 1989).
9 Irish elk, from Anthony D. Barnosky, "Paleo-
ecology and extinction of Irish elk (Megaloceros
giganteus)," lecture at the University of
Washington (13 February 1990); see also his "`Big
game' extinction caused by climatic change: Irish elk
(Megaloceros giganteus) in Ireland,"
Quaternary Research 25:128-135 (1986).
10 Quotation from Edwin Dobb, "The big picture."
The Sciences 29(2):44-50 (1989).
11 Volcano ash potentially rewarming earth by changing
albedo: it all depends on how thick it is, whether it
warms or insulates. The dark medial stripes of many
glaciers, from where lateral debris has collected as
two smaller glaciers merge, often causes the
underlying ice to melt slower than the
surroundings. Glacial "tables" provide another
example: If a rock on the glacial surface cannot warm
up enough during the day to transmit heat to the
underlying ice, then the surrounding ice will melt
faster, leaving the rock atop a pedestal. I thank the
geologist Neil Fahy for pointing this out to me in the
Gulf of Alaska.
11 Stephen E. Zebiak, "Ill Winds: How events in the
tropics throw the world's weather out of whack."
The Sciences 29(2):26-31 (1989). And for
historical data, the news article "La Niña's big chill
replaces El Niño," Science 241:1037-1038 (26
August 1988).
18 W. S. Broecker, letter in Science 245:451 (4
August 1989).
Chapter 2. Incrementing Intelligence:
A Principle of Nature?
20 Francis Bacon, The Advancement of
Learning (1640).
21 Brain/body ratios, see Harry Jerison, Evolution
of the Brain and Intelligence (Academic Press,
1973); for hominid brain/body estimates, see Robert
Foley and Robin Dunbar, "Beyond the bones of
contention," New Scientist 1686:37-41
(14 October 1989), especially the boxed data from
Henry McHenry and Leslie Aiello.
22 Ants are a particularly good example of how
"intelligent" behavior seems to be the collective
property of a minimum number of contributors. See
Thomas D. Seeley and Royce A. Levien, "A colony
of mind: the beehive as thinking machine." The
Sciences 27(4):38-43 (1987). Nigel R. Franks,
"Army ants: a collective intelligence." American
Scientist 77:139-145 (March-April, 1989).
Dictionary definitions of intelligence, cleverness,
etc., are of little help. Some of the more thoughtful
distinctions regarding intelligence are to be found in
Horace B. Barlow's "Intelligence, guesswork,
language," Nature 304:207-209 (1983), and
his entry "Intelligence: The Art of Good Guesswork"
in The Oxford Companion to the Mind, edited
by Richard L. Gregory, pp. 381-383 (Oxford,
1987). But pigeons are pretty good at guessing new
perceptual categories, one of the reasons why I
emphasize inventing and judging "novel courses of
action" as a basic aspect of human intelligent
behavior.
24 W. H. Calvin, The Cerebral Symphony: Seashore
Reflections on the Structure of Consciousness
(Bantam, 1989), chapter 1. In that book and the
present one, I have started the evolution story with the
animals of the last 100 million years; for a more
complete time scale of evolutionary processes, see my
third book, The River that Flows Uphill: A
Journey from the Big Bang to the Big Brain
(Macmillan 1986, Sierra Club Books softcover edition
1987).
26 For a view that says language is the big step to
becoming intelligent, see E. MacPhail, "Vertebrate
intelligence: the null hypothesis." Philosophical
Transactions of the Royal Society of London
B308:37-51 (1985). Tool use isn't necessarily
"intelligent": Benjamin B. Beck, "Tools and
intelligence." In: Animal Intelligence, edited
by R. J. Hoage and Larry Goldman, pp. 135-147
(Washington, D.C., Smithsonian Institution Press,
1986).
27 Oliver Sacks, Seeing Voices: A Journey
Into the World of the Deaf (University of
California Press, 1989), p. 40. Many prelingually-deaf
children raised without Sign will, however, develop
their own "home sign" system of much greater
sophistication than that of their caregivers: see Susan
Goldin-Meadow and H. Feldman, "The
development of language-like communication without
a language model," Science 197:401-403
(1977). While this indicates that the developing brain
can "invent" language without hearing speech, the
prospects of such children are still bleak.
30 W. H. Calvin, "The brain as a Darwin Machine."
Nature 330:33-34 (5 November 1987). An
interesting predecessor from the computer science
community to the Darwin Machine concept can be
seen in John H. Holland, K. J. Holyoak, R. E.
Nisbett, and P. R. Thagard, Induction:
Processes of Inference, Learning, and Discovery
(MIT Press, 1986). Though neither draws explicitly
on the serial-ordered aspect of DNA bases and of
antibody amino acids that characterize darwinism in
our best-understood systems, Holland's genetic
algorithms is the closer analogy to Darwin Machines
creating strings of movement commands than is the
"neural darwinism" seen in Gerald M. Edelman,
The Remembered Present: A Biological Theory of
Consciousness (Basic Books, 1989). My review
of Edelman's earlier book draws some distinctions:
W. H. Calvin, "A global brain theory,"
Science 240:1802-1803 (24 June 1988).
32 Nicholas Keynes Humphrey's book The Inner
Eye (Faber and Faber, 1986) is a good exposition
on the role of social life in shaping up intelligence,
and Frans de Waal's Peacemaking Among
Primates (Harvard University Press, 1989) has
many examples of "look-ahead" in a social setting. If
you want more, there is Machiavellian
Intelligence, edited by Richard Byrne and
Andrew Whiten (Oxford University Press, 1988).
More conventional analyses of animal mentality can
be found in Hoage and Goldman (1986); and
Donald R. Griffin, Animal Thinking
(Harvard University Press, 1984).
37 Charles Darwin, On the Origin of Species
(John Murray, 1859), p. 194.
38 Herbert A. Simon, Models of Thought (Yale
University Press, 1979; first appeared in a 1956
paper), p. 20. Closely related to satisficing is
good-enough engineering, whose physiological
implications are discussed by Lloyd D. Partridge,
"The good enough calculi of evolving control systems:
Evolution is not engineering," American Journal
of Physiology 242:R173-R177 (1982).
39 Copernicus's sun-centered model actually wasn't
simpler than Ptolemy's earth-centered one, because
Copernicus used circular orbits. It wasn't until Kepler
used ellipses that things simplified. See James
Trefil, Reading the Mind of God (Scribner's,
1989).
41 Increasing body size is another drive toward
behavioral complexity, in the analysis of James Tyler
Bonner, The Evolution of Complexity
(Princeton University Press, 1988). But body size is
surprisingly labile: A. M. Lister, "Rapid dwarfing of
red deer on Jersey in the last interglacial,"
Nature 342:539-542 (30 November 1989).
And, for 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).
Some of the Hungary-specific material in this
chapter first appeared in somewhat different form in
my article, "Fast tracks to intelligence (considerations
from neurobiology and evolutionary biology)," in
Bioastronomy -- The Next Steps, edited by G.
Marx (Kluwer, 1988), pp. 237-245.
43 Darwin (1859), p. 191.
46 Flickers, cited in David P. Barash, The Hare and
the Tortoise (Viking, 1986), p. 84.
48 Chewing ends of sticks: Y. Sugiyama et al., "Ant-catching wands of wild chimpanzees at Bossou,
Guinea." Folia Primatologica 51(1):56-60
(1988).
48 Much has been made of the tendency for behavior to
lead the way in evolution ("Free will can guide the
evolutionary process" and other such upbeat
pronouncements). It was first formulated (in
somewhat more obscure terms) in 1894 when three
different scientists discovered it: Henry F. Osborn,
James Mark Baldwin, and Lloyd Morgan. Today it
tends to go under the name "the Baldwin Effect" or
the motto "form follows function." It marks the last
big discovery of the nineteenth-century followers of
Charles Darwin, who clearly laid the foundation for
how we now think about thought processes (I describe
animal decision-making and human Darwin Machines
more fully in The Cerebral Symphony). But
their work was largely forgotten when the early
mutations-are-everything geneticists turned their backs
on Darwin and the psychologists became so enamored
of the behaviorist and Freudian extremes that they
could tolerate no other way of looking at things.
Population thinking, that concern with the changing
statistical profile of whole groups which is the key
feature of darwinism, does not come naturally to most
humans, who more readily identify with an "essence,"
that "typical type." For the Baldwin Effect, see
Robert J. Richards, Darwin and the Emergence
of Evolutionary Theories of Mind and Behavior
(University of Chicago Press, 1987), p. 452.
51 Darwin (1859), p.182. Loren Eiseley, The Man
Who Saw Through Time, (Scribner's, 1973), p. 95.
Chapter 3. Finding a Fast Track to the Big Brain:
How Climate Pumps Up Complexity.
53 Paul Gauguin, as quoted by Humphrey (1986),
pp. 172-173.
55 Reconstructing hominid evolution using cues from the
great apes: see the various contributions in The
Evolution of Human Behavior: Primate Models,
edited by Warren G. Kinzey (State University of
New York Press, 1987).
56 Kenneth Boulding, quoted in The Environmental
Crisis, edited by Harold W. Helfrich (Yale
University Press, 1970), p. 160.
56 Russell H. Tuttle, "The pitted pattern of Laetoli
feet." Natural History (3):60-65 (1990). R.
H. Tuttle, D. M. Webb, and M. Baksh, "The pattern
of little feet." American Journal of Physical
Anthropology 78(2):316 (1989). "The Laetoli G
prints are indistinguishable from those of habitually
barefoot Homo sapiens."
58 Sue Taylor Parker and Kathleen Rita Gibson,
"A developmental model for the evolution of language
and intelligence in early hominids," in Behavioral
and Brain Sciences 2:367-408 (1979), identify
"extractive foraging of embedded foods" as creating
selection for tool use, and so on to intelligence.
58 Chimpanzee sign language references, see
Teaching Sign Language to Chimpanzees,
edited by R. Allen Gardner, Beatrix T. Gardner,
and Thomas E. Van Cantfort (State University of
New York Press, Albany, 1989).
59 Hay plays an interesting role midway in civilization,
as Freeman Dyson notes in Infinite in All
Directions (Harper and Row, 1988). The Roman
Empire didn't need to cut grass in the autumn and
store it for winter "grazing" because in the
Mediterranean basin grass grows well enough in
winter for animals to graze; the idea of hay was
unknown to the Roman Empire but was known to
every village of medieval Europe. Keeping large
numbers of horses and cows alive through the winter
aided in the development of the northern population
centers such as Paris and Berlin, whose economies
came to dominate the Mediterranean ones.
62 Ronald M. Nowak and John L. Paradiso,
Walker's Mammals of the World, 4th edition
(Johns Hopkins University Press, 1983). Black bears
have litters of one to four, usually two or three.
67 Mutation rate, see J. S. Jones, "A tale of three cities."
Nature 339:176-177 (18 May 1989).
69 Loren Eiseley, The Immense
Journey (Doubleday, 1957), p. 51 and p. 54.
72 Herbert A. Simon, Reason in Human Affairs
(Stanford University Press, 1983), p. 44.
72 Woodpeckers' empty niche, see Ernst Mayr,
Animal Species and Evolution (Harvard
University Press, 1963), p. 87.
73 Epidemic originally meant to spread beyond
the local deme; endemic means only within a
local population, as in "this deme is the only one that
exists anywhere," a species unique to the locality.
77 Matt Cartmill, "Misdeeds in anthropology: a
review of Bones, Bodies, Behavior, edited by
George W. Stocking, Jr." Science 244:858-9 (1989).
78 Erik Erikson, Identity: Youth and Crisis
(Norton, 1968).
80 Mayr (1963) p. 371.
81 Most such refuges have been logged off, their
ecosystems greatly disrupted, but a few remain. A
conflict between different branches of science
occurred in the late 1980s, when astronomers wanted
to build yet another telescope atop the mountains of
southern Arizona in the midst of one of the last
Pleistocene refugia, misrepresenting the biologists'
ancient ecosystem concerns as a fight over "just one
more kind of squirrel." The U.S. Congress, familiar
with squirrels but not with ecosystems, overrode the
environmental protection laws in 1988 at the request
of Arizona politicians concerned that the construction
and operations money might go to some other
deserving state without a Pleistocene refuge to destroy.
A partial account can be found in The
Scientist (22 January 1990), pp. 4-5.
The illustration of the last five major ice ages has
been adapted from figures 40 and 48 in Imbrie and
Imbrie (1986); based on cores from the floor of the
Indian Ocean, these records have less regional bias
than the Greenland ice cores (which tend to reflect the
surface temperature of the North Atlantic Ocean) used
for similar illustrations in chapters five and ten.
85 Lewis Thomas, Late Night Thoughts on Listening
to Mahler's Ninth Symphony, (Viking, 1983),
p. 15.
Chapter 4. Neandertal Country:
Some Consequences of a Fickle Climate
87 Heinz Pagels, The Dreams of Reason (Simon
and Schuster, 1988), p. 161.
88 John Imbrie and Katherine P. Imbrie, Ice
Ages (Harvard University Press, 1986); the
Milankovitch quote is from pp. 102-103.
89 R. E. Edwards, J. H. Chen, T.-L. Ku, and G. J.
Wasserburg, "Precise timing of the last interglacial
period from mass spectroscopic determination of
Thorium-230 in corals." Science 236:1547-1553 (19 June 1987).
The illustration of encephalization quotient is taken
from the work of Henry McHenry and of Leslie
Aiello featured in the New Scientist of 14
October 1989, p. 39.
90 Erik Trinkaus, "The fate of the Neandertals."
Lecture at University of Washington (6 February
1990); see his "The Neandertals and modern human
origins," Annual Review of Anthropology
15:193-218 (1986).
90 Stature in aboriginal groups, see K. L. Beals, C. L.
Smith, and S. M. Dodd, "Brain size, cranial
morphology, climate, and time machines."
Current Anthropology 25:301-330 (1984).
93 Gracile chimpanzees, see Adrienne L. Zihlman,
John E. Cronin, D.L. Cramer, and Vincent M.
Sarich, "Pygmy chimpanzee as a possible prototype
for common ancestor of humans, chimpanzees and
gorillas." Nature 275(5682):744-0746 (1978).
Randall L. Susman, "Pygmy chimpanzees and
common chimpanzees: models for the behavioral
ecology of the earliest hominids," in The Evolution
of Human Behavior: Primate Models, edited by
Warren G. Kinzey (State University of New York
Press, 1987), pp. 72-86.
95 "Juvenile playing-around tendencies" may be useful
for discovering a new niche, but aren't as likely to be
important for the maintenance of it, if culturally
enlightened robusts can equally well exploit it. My
guess is that shortened generation time was typically
the major factor, with some other aspect of juvenilized
brains maintaining the gracile form in the face of
harder times.
96 Charles Darwin, as quoted by Ernst Mayr in
Scientific American (March 1990), p. 37.
97 The quote is from Stephen Jay Gould's column in
Natural History (November 1986), p. 28. The
basic reference on brain/body ratio is Jerison (1973).
97 "Features by which humans differ from apes...." For
starters, see the list in Richard D. Alexander's
Darwinism and Human Affairs, (University of
Washington Press, 1979), pp. 209 ff.
98 Alister Hardy's hypothesis can be best read in
Elaine Morgan's The Aquatic Ape (Stein and
Day, 1982); see her regular updates in New
Scientist. For some aspects of aquatic ape
proposals and their chronology, see Mile 136-137 of
my 1986 book, The River that Flows Uphill.
For bonobos (the gracile chimpanzees) as evidencing
some aquatic adaptations, see Frans de Waal's
Peacemaking Among Primates (Harvard
University Press, 1989), pp. 183-186.
98 Savannah theory restatement: C. Owen Lovejoy,
"The origin of man." Science 211:341-350
(23 January 1981).
100 "20 percent of land covered..." About 10 million
square miles of land are covered at the peak of an
ice age (see Imbrie and Imbrie, 1986). My
calculation goes as follows: Subtracting 5 million
for uninhabited Greenland, Canada, and the
northern U.S. leaves 5 million for covering
northern Europe and Asia. Europe-Asia-Africa
total 32 million square miles, though perhaps a
third of Africa and of Central Asia is only
marginally habitable. Thus 5 million reduces the
inhabitable 25 million by 20 percent; a meltback
would expand the remaining core by 25 percent.
102 Latitude effect on stature summarized by Beals
et al. (1984).
102 Calories from gathering vs. hunting, see Richard
B. Lee, in Man the Hunter, edited
by R. B. Lee and I. DeVore. (Aldine, 1968)
pp. 30-48.
103 No, I'm not slighting the southern mid-latitudes in
temperate zone roles: neither New Zealand nor
Chile-Argentina had hominids until 1,200 and
31,000 years ago, respectively, after modern
Homo sapiens arrived.
107 "This pump is even simpler than Darwin's": Note,
however, that this expand-the-periphery but
compress-the-center principle won't work in every
case of population fluctuation. The dramatic
frontier-type advantage is dependent on the
relative rates of frontier movement (the no-land-rush qualification); it may not apply to the end of
a drought where the remaining population can
quickly space itself out to occupy the newly
productive land. And it depends on shaping up a
somewhat different frontier genome by special
selection pressures (the annual round of selection
associated with winter); the margins of a drought-devastated region are unlikely to present
opportunities comparable to the herds of
megafauna attracted by the good grazing on the
glacial margins.
Still, though dramatic accelerations of gradual
evolution depend on such qualifications about the rates
at which frontiers move and specialize, pumping the
periphery of the habitat may be a more general
principle relevant to the slower evolution of many
species: selection pressures are always the most
severe where the species is precariously adapted to its
niche, such as at the margins of a habitat. Because
climates are always fluctuating to cause substantial
alterations in the habitat size and thus population
levels (e.g., El Niño causes population crashes among
Pacific birds and fish), the frontier-type representation
in the total genome may be pumped up repeatedly
even in the general case.
This is a simple model, assuming a doughnutlike
arrangement: a ring around the outside of the main
population with 15 percent of the total area. In real
life, it was surely more complicated, if only from the
geography having inhabitable areas. As the crows of
Europe demonstrate, temperate zone species may be
pushed south into refugia that are isolated from one
another (eastern and western Mediterranean
peninsulas), rather than continuously spread around a
single ring. While there is some tendency for
temperate zone and central populations to constantly
mix, this stirring of the gene pool will be minimized
during the expansion phase, the crucial period for this
analysis. The invention of boats during the most
recent glaciation may have promoted greater mixing of
peripheral and central populations.
Fragmentation of the frontier has two
consequences, both of which speed up evolution even
more. Speciation becomes more likely, as in the
crows. And secondly, the contracted population has
more of its population living on a margin of the
habitat than they would joined into one continuous
ring -- and if one lives on the margins of the range,
living conditions are marginal. The perimeter-to-population ratio (just a special case of surface-to-volume ratio reasoning) would be even higher, with a
higher percentage of the population living in marginal
circumstances that speed up natural selection's
modifications to the population.
Francis Bacon and Charles Darwin speculated
on reasons for the frequent dominance of northern
faunas over southern: see Loren Eiseley,
Darwin's Century (Doubleday, 1958),
pp. 10-11. For flora, however, Europe is something of
a special case, with many fewer species of plants than
North America or east Asia. As the British botanist
Charles Turner explained ("Plant extinctions of the
European Quaternary," lecture at University of
Washington, 9 January 1990), this is probably because
the Mediterranean limits the southern retreat of species
during an ice advance, so that species go extinct more
readily there rather than surviving in refugia. For a
review of how gene flow and regional specialization
interact, see N. H. Barton and G. M. Hewitt,
"Adaptation, speciation, and hybrid zones,"
Nature 341:497-503 (12 October 1989).
108 Speciation is, in a sense, more common in the
relatively static tropics -- the way that every
valley in Hawaii seems to have its own endemic
species of fruit fly. But my argument on
reproductive quasi-isolation in islandlike refugia
seems particularly appropriate to temperate-zone
hominid evolution, given that the various isolated
groups are always coming back to potentially
intermix with each other at each major meltback:
whatever reproductive isolation is achieved during
geographic isolation will serve to limit backsliding
during boom times.
107 Because there is no land for interglacial expansion
in Africa, southern Africa might house the most
conservative type in spite of its borderline-temperate climate; because of the bottleneck at
Suez, Africa might also be invaded more slowly
from Eurasia than in a simple model. Southern
Africa does have one of the oldest types of
mtDNA: Rebecca L. Cann, Mark Stoneking,
and Allan C. Wilson, "Mitochondrial DNA and
human evolution," Nature 325:31-36 (1
January 1987). "All these mtDNAs stem from
one woman who is postulated to have lived about
[150,000] years ago, probably in Africa." But just
as an English surname may disappear from the
church records following generations of all female
offspring, so a woman with a rare mtDNA allele
may fail to pass it on if only her sons grow up to
reproduce. Such loss of alleles in clonal lineages
reduces variability; one would expect such loss to
be exaggerated in small temperate zone
populations, compared to the tropical demes.
Such effects could give rise to a substantially
different interpretation of where ancestors lived.
The "Eve" interpretation of the mtDNA analyses
is quite misleading; to say that all modern peoples
have one common ancestor that lived about 150,000
years ago is only to restate the initial
assumption of genetic drift. There were many
women then living, and their nuclear DNA is
to be found in all of us. It's just that the mtDNA
inheritance is odd in two ways: the genes aren't
regularly shuffled, and they are inherited only from
one's mother. Because of this, some variants die out.
In a population of n mothers, each of whom
produces on average one daughter, it will take about
2n generations for the mtDNA from n-1 of the original mothers to die out via having only
sons at some generation along the way. Though the
tree-making model itself is most helpful in suggesting
when migrations might have occurred, focussing on its
singular root is nonsensical; all it tells you is that the
genetic drift method is useless for dates older than
150,000 years (just as the carbon-14 dating methods
are no good for dates older than about 70,000 years).
108 Punctuated equilibrium: Stephen Jay Gould, in
Perspectives on Evolution, edited
by R. Milkman (Sinauer, 1982), pp. 83-104.
108 Note that the selection pressures seasonally
present at the margins of the habitat could be far
more influential than the everyday selection
pressures of the average habitat, e.g., infrequently
used hunting skills might evolve more rapidly
than frequently needed gathering skills in the total
population, simply because of ice-age cycling.
For hominid evolution, this disassociation
promises to create severe difficulties for
interpreting fossils: the living conditions when
bones were deposited in the African savannah
might be unrepresentative of those at the distant
margins of the habitat where features were most
effectively shaped. Similarly, where less-modified
genes can still be found need not mean that this
locale was where the ancient genome was shaped
up, or where speciation occurred.
109 Dating of the earliest spread of hominids out of
Africa is reviewed by Richard G. Klein in his
text The Human Career (University of
Chicago Press, 1989).
111 Loren Eiseley, The Immense Journey
(Doubleday, 1957), p. 55.
Chapter 5. Over the Pole: Surveying the
Ice Ages from a Seat in Heaven . . . . . .
113 Robert Ardrey, introduction to Eugène N.
Marais, The Soul of the Ape (1969),
p. 21 of the 1973 Penguin edition.
Peter Wadhams, "Evidence for thinning of the
Arctic ice cover north of Greenland," Nature
345:795-797 (28 June 1990).
114 A brief introduction to the glaciations is John
Gribbin, "The end of the ice ages?" New
Scientist 1669:48-52 (17 June 1989). The
extensive popular treatment is John Imbrie and
Katherine P. Imbrie, Ice Ages
(Harvard University Press, 1986), pp. 102-103. D.
R. Lindstrom and D. R. MacAyeal,
"Scandinavian, Siberian, and Arctic Ocean
glaciation: Effect of Holocene atmospheric CO2
variations." Science 245:628-631 (1989).
The beginning of the ice age at 2.5 million years
is dated by N. J. Shackleton, J. Backman, H.
Zimmerman, D. V. Kent, M. A. Hall, D. G.
Roberts, D. Schnitker, J. G. Baldauf, A.
Desprairies, R. 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
342:133 (1989).
115 Fridtjof Nansen: See my notes in The
Cerebral Symphony, pp. 352-353.
117 M. Milankovitch, Canon of Insolation and
the Ice Age Problem (Königlich Serbische
Akademie, 1941; English translation by the Israel
Program for Scientific Translations, 1969).
Joseph 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.
COHMAP members, "Climatic changes of the last
18,000 years: Observations and model simulations."
Science 241:1043-1052 (1988).
118 Iceland's volcanos, see John McPhee's The
Control of Nature (Farrar Straus Giroux,
1989).
121 For the fourfold rate differences, see John Imbrie
and John Z. Imbrie, "Modeling the climatic
response to orbital variations," Science
207:943-953 (1980). There are, however, some
significant nonlinearities associated with melting.
The coastal glaciers provide an important example
of modes of operation. Even when rainfall and
temperature are shared by neighboring glacial
systems, as at Glacier Bay National Park near
Juneau, Alaska, some will be in "retreat mode"
and others in "advance mode." If a glacier has
retreated far enough back up its valley, the next
advance will plow a terminal moraine -- that
serves as a coffer dam when reaching the sea,
allowing the glacial snout to push far offshore.
This makes it difficult for seawater to erode
beneath the glacier. When water finally comes in
over the top of the coffer dam, one gets a
"tidewater glacier." They are an anomaly, cliffs
ten stories high above the waterline dropping
blocks of ice into the sea. They may have twice
as many stories below sea level, with the
submerged snout extending far out from the
"shoreline". Once sea water does penetrate
beneath the submerged section of glacier (and
great icebergs begin popping to the surface!), the
glacier will rapidly retreat until only a tip is
touching the shoreline -- and be unable to advance
again to form an ice cliff, at least until retreating
far enough to build up another terminal moraine.
There may be similar state-dependent situations in
the ocean-ice-atmosphere system more generally.
122 W. R. Peltier, "Slow changes in the earth's shape
and gravitational field: constraints on the
glaciation history and internal viscoelastic
stratification." Space Geodesy and
Geodynamics (Academic Press, London,
1986), pp. 75-109.
122 When northern glaciers melt back in response to
changes in summer sunshine, so do the southern
hemisphere glaciers of South American and New
Zealand, as Stephen G. Porter points out. That
suggests that the northern meltoff is affecting
global climate in a big way, overriding the effects
of the minimal summer sunshine of the Southern
Hemisphere.
49 Greenhouse warming and the chance of triggering
another Dryaslike shutdown of the North Atlantic
Current: Uwe Mikolajewicz, Benjamin D. Santer,
and Ernst Maier-Reimer, "Ocean response to
greenhouse warming," Nature 345:589-593 (14
June 1990), do not discuss the Dryaslike episodes, but
their simulations of ocean currents do show the
decreased North Atlantic deep water production and
decreased salinity of surface waters there that
Broecker and Denton (1989) identify as precursors
of a shutdown.
123 Intermediate meltoffs best correlated with June-July perihelion: from a lecture by the French
glacial expert, Robert J. Delmas, "Climatic and
environmental information from ice cores."
Lecture at University of Washington (14 February
1989).
123 Paul Hoffman's piecing-together of the mosaic
geology of Archean North America, Greenland,
and Scandinavia is covered in a news story in
Discover, (February 1990), pp. 26-27.
126 John Gribbin and Mary Gribbin, "Climate and
history: the Westviking's saga." New
Scientist 1700:52-55 (20 January 1990).
Settlement of Greenland and windows of
opportunity from climate change in the North
Atlantic. The illustration of medieval-to-modern
temperatures of the North Atlantic Ocean is
modified from their sidebar.
127 Aurora, see Syun-Ichi Akasofu, "The dynamic
aurora." Scientific American 260(5):90-97
(May 1989). Solar output also varies, with
implications for climate: Richard R. Radick, G.
W. Lockwood, and Sallie L. Baliunas, "Stellar
activity and brightness variations: a glimpse at
the sun's history." Science 247:39-44
(5 January 1990)
130 Ice-free corridor opening dates: Lionel E.
Jackson, Jr., and Alejandra Duk-Rodkin,
"Geology of the ice-free corridor," talk at
University of Washington (19 January 1988), and
John Ives, Alwynne B. Beaudoin, and Martin
P. R. Magne, "Evaluating the role of a western
corridor in the peopling of the Americas,"
Circum-Pacific Prehistory Conference,
(Lecture in Seattle, 3 August 1989; to be
published by Washington State University Press).
The illustration of the ice-free corridor and
Clovis-Folsom sites was adapted from the more
detailed figure of Wendorf (1989).
132 Earliest human habitation dates in the Americas:
Roger Lewin's news article "Skepticism fades
over pre-Clovis man." Science 244:1140
(9 June 1989).
133 Richard E. Leakey on widespread disappearance
of predecessor hominid populations: lecture in
Seattle, Washington (25 February 1989).
137 Benjamin Thompson (Count Rumford), quoted
by Warren M. Washington in Natural
History (March 1990), p. 68.
139 Wallace S. Broecker and George H. Denton,
"What drives glacial cycles?" Scientific
American 262(1):48-56 (January 1990),
pp. 55-56. For a paleosalinity story, see David
A. Anati, "Red Sea Salinity." Nature
339:20-21 (4 May 1989).
The illustration of winter ice extent was adapted from
Fig. 6 in the review of Broecker et al. (1985).
143 Rebounding bluffs, from a lecture by Stephen C.
Porter, director of the Quaternary Research
Center, University of Washington (May 1989).
145 Seattle tombstone-cum-park-bench:
Robert Fulghum, in It Was On Fire When
I Lay Down On It (Villard, 1989), pp. 209-210, may have remembered the quotation
incorrectly -- but not the sentiments! The
tombstone is not entirely anonymous: the
surname Whitebrook can be inferred from the
family plot.
146 Puget lobe of Cordilleran glacier, see Robert
Burns, The Shape and Form of Puget
Sound (University of Washington Press,
1985); Thomas A. Terich, Living with the
Shore of Puget Sound and the Georgia Strait
(Duke University Press, 1987). Ocean circulation
theory, see Broecker and Denton; their figure
on p. 52 shows the advance and retreat of
Washington State glaciers.
Chapter 6. Mount Rainier:
Growing Up in a Boom Time
149 Charles Darwin, On the Origin of
Species (John Murray, 1859), pp. 481-482.
155 James Hanken, "Development of evolution in
amphibians." American Scientist 77:336-343 (July 1989). R. D. Semlitsch and H. M.
Wilbur, "Artificial selection for paedomorphosis
in the salamander Ambystoma
talpoideum." Evolution
43(1):105-112 (1989).
156 Stephen Jay Gould, Ontogeny and
Phylogeny (Harvard University Press, 1977),
pp. 177 ff.
157 Walter Garstang, Larval Forms With
Other Zoological Verses (Basil Blackwell,
1951), p. 62.
157 Adult development finally implementing typically
truncated features, see Aldous Huxley's
cautionary novel After Many a Summer Dies
the Swan (Harper, 1939).
158 Juvenile advantages in adulthood: I discuss this
in The Throwing Madonna: Essays on the
Brain (Bantam, 1991), chapter 3.
158 The first species to fill a "new niche" may, of
course, not be able to hold it, e.g., the grasslands-to-forest succession.
159 Clifford J. Jolly and Jane E. Phillips-Conroy,
"Bulls, bears and baboons: the evolutionary
significance of developmental plasticity."
American Journal of Physical
Anthropology 75(2):227 (1988). Robert M.
Sapolsky, "Lessons of the Serengeti." The
Sciences (May/June 1988). See also his "Junk
food monkeys," Discover 10(9):48-51
(September 1989). Jeanne Altmann has shown
that garbage-fed baboons mature faster and have
more babies, and Sapolsky has found that they
have cholestrol levels one-third higher than
savanna baboons (see Natural History,
May 1990, p. 107 for a picture).
160 Animals that adjust their reproductive policy, see
Paul Colinvaux, Why Big Fierce Animals
Are Rare (Princeton University Press, 1978),
p. 16.
165 Supernormal releasers and attractors, see David P.
Barash, The Hare and the Tortoise
(Viking, 1986), pp. 84-86, and Annie Dillard,
The Writing Life (Harper and Row, 1989),
p. 18. These behavioral attractors are quite
different from the "strange attractors" of chaotic
systems, more like the attractions of quicksand
than the "gravitational centers" of chaos.
30 David Brin, "Neoteny and two-way human sexual
selection" (unpublished manuscript, 1990). Brin's
suggestion that juvenilized appearance in females
might preferentially attract nurturing males has several
interesting consequences, as he points out: it helps to
explain the unusual (compared to other mammals)
amount of attention-attracting female adornment
(which currently supports an enormous cosmetics and
fashion industry), and it helps to explain pedophilia.
If male preference for juvenile-appearing females
coevolved with paedomorphosis, then one might
expect more than the usual (for other primates)
amount of misplaced sexual attraction toward
juveniles. Brin suggests that the unusual-for-mammals
breasts of the human female (which are 85 percent fat
pad) might serve as a sexual releaser, helping the
sexually-interested male to distinguish between
appropriate and inappropriate juvenile-appearing
females.
168 Adolescent growth spurt, see J. M. Tanner,
Foetus into Man: Physical Growth from
Conception to Maturity. (Harvard University
Press, 1978), p. 14. Growth in general (and
models for the adolescent growth spurt associated
with sexual maturity, in particular): Barry
Bogin, Patterns of Human Growth
(Cambridge University Press, 1988). For juvenile
periods of various species, see P. H. Harvey and
T. H. Clutton-Brock, "Life history variation in
primates." Evolution 39:559-581 (1985).
Juvenilization, neoteny, and paedomorphism are
not really synonymous. See Bogin (1988, p. 71),
Gould (1977, p. 179), Ashley Montagu,
Growing Young (McGraw-Hill, 1981),
and F. Harvey Pough, John B. Heiser, and William
N. McFarland, Vertebrate Life, 3rd edition
(Macmillan, 1989, p. 68).
My own summary of the confusing terminology:
what is here called paedomorphosis ("child-shaped") or juvenilization is simply descriptive
of the appearance of the end-product, without
implication of mechanism. Lately neoteny has
been used by some, but not all, authors to refer to the
slowing ("retardation") of somatic development.
Progenesis, on the other hand, refers to
paedomorphosis associated with accelerated somatic
development plus the truncation of ontogeny. Thus,
compared to the apes, we are both neotenized (somatic
development retarded to half the pongid rate) and
paedomorphic. But compared to modern-type
Homo sapiens earlier in the last ice
age, we exhibit progenesis in the same sense as,
compared to wild-types, the domestic animals exhibit
progenesis.
168 For the invertebrate-to-chordate transition, see Q.
Bone, The Origin of Chordates (Oxford
University Press; Carolina Biology Readers #18,
1979), or p. 70 of Pough (1989).
171 C. Loring Brace, Karen R. Rosenberg, and
Kevin D. Hunt, "Gradual change in human tooth
size in the late Pleistocene and post Pleistocene."
Evolution 41:705-720 (1987). And C.
Loring Brace, The Stages of Human
Evolution, 3d edition (Prentice-Hall, 1988) --
though, as Kathleen Gibson notes (personal
communication, Cascais, Portugal, 22 March
1990), simple truncation of tooth growth by
precocious puberty will not explain tooth size
reduction, as tooth size is seemingly determined
much earlier in childhood. James M. Calcagno,
Mechanisms of Human Dental Reduction
(University of Kansas Publications in
Anthropology No. 18, 1989). One of the hazards
of the simplified treatment of early puberty which
I and others utilize is that it leads us to think of
early puberty occurring as if the living conditions
suddenly improved at the time of truncation --
when, of course, they are usually spread out over
the previous decade and influence somatic growth
as well as menarche.
173 Rose E. Frisch, "Fatness and fertility."
Scientific American 258(3):88-95 (March
1988). See also Science 185:949-951 (13
September 1974), and 199:22-30 (6 January
1978).
174 Deer on the Kaibab Plateau of Arizona, see John
P. Russo, "The Kaibab North Deer Herd," a 1964
publication of the Arizona Department of Fish and
Game.
174 Humans perhaps too K-selected, see
Lovejoy (1981).
177 Jerome Kagan, J. Steven Reznick, and Nancy
Snidman, "Biological Bases of Childhood
Shyness." Science 240:167-171 (8 April
1988).
178 Victor H. Dennenberg, "Hemispheric laterality
in animals and the effects of early experience."
Behavioral and Brain Sciences 4(1):1-50
(March 1981).
179 Richard D. Alexander, The Biology of
Moral Systems (Aldine de Gruyter, 1987),
p. 23.
180 The "28-year-old grandparent" phenomenon has
been commented upon by people who work in
hospital maternity wards, e.g., Melvin Konner,
Becoming a Doctor: A Journey of Initiation
in Medical School (Viking, 1987).
181 Susan Oyama, The Ontogeny of Information:
Developmental Systems and Evolution
(Cambridge University Press, 1985), p. 188.
Chapter 7. Whidbey Island:
Ratcheting Up Brain Size
183 Leonard A. Sagan, "Family ties." The
Sciences 28(2):20-29 (March 1988).
189 Ruth Kirk with Richard Daugherty,
Exploring Washington
Archaeology. (University of Washington
Press, 1978). Note that ice age fishing villages
would have been covered up by rising sea level,
unless the land uplifted at a faster pace. There
are some sites along the Alaskan panhandle
coastline where uplift could have preserved an
early Holocene fishing village: Bruce F.
Molnia, "Glacial history of the northeastern Gulf
of Alaska: A synthesis." In Glaciation in
Alaska: The Geologic Record, edited by
T. D. Hamilton, K. M. Reed, and R. M. Thorson
(Alaska Geological Society, 1986), pp. 219-236.
190 Death in childbirth, see Sue Armstrong, "Labour
of death," New Scientist 1710:50-55 (31
March 1990). "All but 1 per cent of these
maternal deaths take place in the Third World,
where the average lifetime risk of dying as a
result of pregnancy is between one in 25 and one
in 50; this compares to a lifetime risk of between
one in 4000 and one in 10,000 for a woman in the
developed world."
191 Hat size and IQ, see Stephen Jay Gould,
The Mismeasure of Man.
(Norton, 1981).
191 Kin selection by big heads, see W. H. Calvin,
"The great encephalization: throwing,
juvenilization, developmental slowing, and
maternal mortality roles in prehuman brain
enlargement." Human Ethology
Newsletter 5(3):4-6 (September 1987). And
also W. H. Calvin, "Of fast teeth and big heads."
Nature 328:481 (6 August 1987).
193 Despite our perceptual abilities to guess a racial
designation from a collection of traits such as skin
color, hair color and stiffness, eye color, and
facial shape, the serious study of the subject
suggests that we are simply inventing pigeonholes
("categorical perception") along a continuous
distribution of traits. There is, however, a
tendency called assortitive mating where people
tend to pick mates for themselves or their children
on the basis of physical similarity; this tends to
maintain distinctive groupings of physical
traits that might arise by chance. Such
considerations of "beauty" may be simple sexual
selection with no rhyme or reason -- but sexual
selection often has some natural selection
rationale, however exaggerated and inappropriate
the extremes to which it is taken (those long or
iridescent bird tails probably started out as simple
female preference for mates healthy enough to
grow new feathers; women in many parts of the
world prefer tall men as mates, stature being an
indirect indicator of successful childhood
development).
And the birth canal bottleneck could be the
rationale for some such human mate selection, given
how obstetricians worry about difficult deliveries
when the wife is petite and the husband isn't. Any
random (but heritable) tendency to select a body type
similar to one's parents or siblings would be reinforced
by improved survival of offspring and mothers. And
so the birth canal bottleneck might have helped
maintain local standards of "beauty" (and, alas,
reinforced racism).
194 Heritability of early menarche: Tanner (1978),
p. 126.
195 Herbert A. Simon, Reason in Human
Affairs (Stanford University Press, 1983),
p. 50.
195 F. Brown, J. Harris, R. Leakey, and A.
Walker, "Early Homo erectus skeleton
from west Lake Turkana, Kenya."
Nature 316:788-792 (1985).
195 Secular trend in height, see Tanner (1978),
p. 150.
196 Peter K. Stevens, Patterns in Nature
(Little, Brown 1974), p. 25.
199 Theodosius Dobzhansky, "Discussion." In
Insect Polymorphism, edited by J. S.
Kennedy (Symposia of the Royal Entomological
Society, 1961), p. 49.
201 James Lovelock in The Ages of Gaia
(Norton, 1989) gives a nice treatment of those
population boom-and-bust equations for general
readers.
201 Oscillations in population size, see Paul
Colinvaux, Introduction to Ecology
(Wiley, 1973), pp. 483-485.
201 How might domestication thoroughly embed a
juvenilized form of the species if natural selection
operated upon the r-shift itself? This is
somewhat like asking why those invariably-aquatic axolotls might have evolved from those
conditionally aquatic Ambystoma -- again
it is a question of how the conditional feature
might have been lost without natural selection for
losing it.
It's potentially like that recessive gene which,
when two are present, causes sickle-cell anemia -- but
when only heterozygous, protects against malaria (and
so is selected for, in low-lying tropical areas with the
mosquitos that spread malaria). Only in my theory,
the homozygous condition causes sure-fire acceleration
rather than the conditional-on-climate acceleration of
the heterozygous case.
Ordinarily you'd think that the natural selection
would operate on the flexibility, so that the body
features would spring back to the old average once the
climate stabilized at a new mean. But there are some
ways in which accelerated maturity might become
unconditionally established despite an origin in a
series of conditional r-shift events. Suppose
we have one version (allele) of a developmental rate
gene that, when homozygous (the individual has two
copies and so no other choices), leads to accelerated
maturity. When neither allele at this position in the
chromosome is the special allele, one gets average
developmental rates. But if one version is present,
and the other is the standard allele, one gets a
precarious balance between acceleration and standard.
And so the special accelerated version is conditionally
used: the occasions being when the environment
improves (the better nutrition, increased daylight,
higher population density, or whatever). Since the
phenotypes will be more successful under such
conditions, the allele will become more and more
common in the general population. Some individuals
will become homozygous for it, and thus always
accelerated in maturity, unconditionally juvenile in
adult appearance.
202 The enormous plasticity of adult body size can be
seen in the poorly-understood reduction in body
size of mammals in isolated demes; pygmy races
of elephants and rhinoceros have been found on
islands. But it wasn't until someone studied
fossils of the European red deer on Jersey that we
realized how fast body size could change, absent
artificial breeding: 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). Was this due to resource
limitations? Lack of predators? No one is sure;
were there a boom-time due to omission of
predators or pathogens from the new island,
juvenilized variants that reach reproductive age
sooner might come to eventually dominate the
gene pool (because they have more offspring per
century than those with standard menarche). Note
that lack of certain pathogens (one of the virtues
of isolation) might allow small adults to more
successfully raise offspring; lack of predators per
se is not required. After the glaciers again
lowered sea level to reconnect Jersey to the
mainland, the dwarf deer disappear from the fossil
record.
204 Eiseley (1957), p. 125, pp. 129-131.
Chapter 8. Hand-ax Heaven:
The Ambitious Ape's Guide to a Bigger Brain
206 Ernst Mayr, Toward a New Philosophy of
Biology (Harvard University Press, 1988),
p. 95.
207 Mastodon: Kirk and Daugherty (1978), p. 28.
208 Ernst Mayr, "Descent of man and sexual
selection." In L'Origine dell'
Uomo (Academia Nazionale dei Lincei, 1973),
pp. 33-61.
209 Tool-use by animals, see pp. 575-578 of The
Oxford Companion to Animal Behaviour,
edited by David McFarland (Oxford University
Press, 1987).
209 Christophe Boesch and Hedwige Boesch, "Sex
differences in the use of natural hammers by wild
chimpanzees: a preliminary report."
Journal of Human Evolution
10:585-593 (1981), and film shown at Tools,
Language, and Intelligence: Evolutionary
Perspectives workshop in Cascais, Portugal
(19 March 1990).
209 Cooperative hunting: Shirley C. Strum,
"Baboon cues for eating meat." Journal
of Human Evolution 12:327-336 (1983).
Geza Teleki, "The omnivorous chimp."
Scientific American 228(1):32-42
(1973). Frans X. Plooij, "Tool-use during
chimpanzee's bushpig hunt." Carnivore
1:103-106 (1978). C. Boesch and H. Boesch,
"Hunting behavior of wild chimpanzees in the Taï
National Park." American Journal of Physical
Anthropology 78:547-573 (1989).
210 Throwing by chimpanzees, see Plooij (1978);
Jane Goodall, In the Shadow of Man
(Houghton Mifflin, 1971) and The
Chimpanzees of Gombe (Harvard University
Press, 1986), p. 550; and Frans de Waal,
Chimpanzee Politics: Power and Sex Among
Apes (Harper and Row, 1982).
211 Chimpanzees throw in a variety of humanlike
styles, see Jane Goodall, "The behaviour of
free-living chimpanzees in the Gombe Stream
Preserve." Animal Behaviour Monographs
1(3):161-311 (1968) at p. 203. But, as Sue
Savage-Rumbaugh pointed out to me, many of
those postures are associated with male threat
displays and are unlikely to be associated with
"get set" styles that might lead to precision
throwing.
The illustration of Acheulian "hand axes" is adapted
from drawings by C. O. Waterhouse at the British
Museum (Natural History). The smaller one is a
"twisted ovate" from St. Acheul, France. The larger
is the one associated with the Swanscombe skull in
England. While the Acheulian tool kit went out with
Homo erectus, bifaces shaped like Acheulian
hand axes are also seen in Homo sapiens tool
kits, e.g., the one from Le Moustier at Musée de
l'Homme in Paris).
214 H. G. Wells, Tales of Space and Time
(Doubleday and McClure, 1899); for a general
introduction to hand axes and the associated
toolmaking styles, see John Gowlett, Ascent
to Civilization (Knopf, 1984), pp. 60 ff.
Eileen M. O'Brien, "The projectile capabilities of
an Acheulian handaxe from Olorgesailie."
Current Anthropology 22:76-79 (1981);
and "What was the Acheulean hand ax?"
Natural History 93:20-23 (1984). Spin
for throwing into flocks of birds: M. D. W.
Jeffreys, "The hand bolt." Man 65:154-154 (1965).
214 Hand axes in dried-up ponds, etc.: Glynn Ll.
Isaac, Olorgesailie. (University of
Chicago Press, 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
11:176-187 (1976).
215 William D. Hamilton III, "Geometry for the
selfish herd." Journal of Theoretical
Biology 31:295-311 (1971).
216 William H. Calvin, "A stone's throw and its
launch window: timing precision and its
implications for language and hominid brains."
Journal of Theoretical Biology
104:121-135 (1983). And my subsequent book
The River that Flows Uphill: A Journey from
the Big Bang to the Big Brain (1986).
219 The big cats sometimes leap onto the back of a
much larger herd animal and bring it down; the
cat's claws might active the same withdrawal
reflex that lowers the hindquarters.
219 Patrick D. Wall, "On the relation of injury to
pain." Pain 6:253-264 (1979).
221 "Killer Frisbee": Albert Leo of Pomona College
suggested this name (June, 1988), which is sure to
be disavowed by anthropologists.
222 "Manuports," see Mary D. Leakey, Olduvai
Gorge. Vol. 3. (Cambridge University Press,
1971).
222 Barbara Isaac, "Stone throwing and human
evolution." Unpublished MS; see news article in
Discover 7(6):6-7 (June 1986).
226 Pruning of connections in cerebral cortex is
reviewed in The Cerebral Symphony,
p. 165, 362. The loss of neurons is from J. B.
Lohr and D. V. Jeste, "Studies of neuron loss
with age in three different brain regions in
humans," Society for Neuroscience
Abstracts 15:22 (1989). For monkey motor
cortex, see J. Tigges, J. Herndon, and Alan
Peters, "Neuronal changes in Area 4 during the
life span of the rhesus monkey," Society for
Neuroscience Abstracts 15:259 (1989); they
report that this movement control area of the leg
loses nearly a third of its neurons between infancy
and early adulthood [my wife suggests that the
monkeys must have killed off their clumsy
neurons!].
The illustration of synaptic density in visual cortex
uses the human data of P. R. Huttenlocher,
"Synapse elimination and plasticity in developing
human cerebral cortex." American Journal of
Mental Deficiency 88:488-496 (1984). The
monkey data is from 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). I have replotted
the data to normalize peaks and used a logarithmic
time scale starting at about 120 days after conception
and ending about ten years after birth. In addition to
breaking synapses and withdrawing axon collaterals,
there is also some cell death in cerebral cortex during
the same period. The lateral shift in the human curve
relative to the monkey curve would be consistent with
a two- to three-fold slowing of human somatic
development.
227 Paul Cheney and Eberhard E. Fetz,
"Comparable patterns of muscle facilitation
evoked by individual corticomotoneuronal (CM)
cells and by single intracortical microstimuli in
primates: evidence for functional groups of CM
cells." Journal of Neurophysiology
53:786-804.
229 Not all hunters are male: see A. Estioko-Griffin,
"Daughters of the forest." Natural
History 95(5):36-43 (1986).
232 Eiseley (1957), p. 140
Chapter 9. San Juan Ferry:
Does Consciousness Emerge from Cortical
Consensus?
240 Dean Falk, "Brain evolution in Homo:
The `radiator' theory." Behavioral and Brain
Sciences (in press, 1990).
242 Jeffrey T. Laitman, "The anatomy of human
speech." Natural History 93(8):20-27,
1984. And Phillip Lieberman, The Biology
and Evolution of Language (Harvard
University Press, 1984)
251 From an entirely different perspective, involving
cortical injuries and developmental abnormalities,
the neuropsychologist Marcel Kinsbourne also
arrives at the suggestion that conscious attention
corresponds to the widespread activation of many
regions of cerebral cortex (the quote is from
"Integrated field theory of consciousness," in
Consciousness in Contemporary Science,
edited by A. J. Marcel and E. Bisiach
(Clarendon Press, Oxford, 1988), pp. 239-256.
The philosopher Daniel C. Dennett emphasizes
that conscious perception takes time, much more
than any of the component processes; again, this
can be predicted from Darwin Machine reasoning
applied to both sensory and movement schema
sequences, as it takes many Darwin Machine
generations to achieve a widespread consensus
(Bellagio workshop on consciousness, 26-31 March 1990). Hierarchies, such as the
acoustics-phonemes-syntax-semantics levels of
analysis which seem to help us understand
sentences, may be helped by Darwin Machine
architectures that can be parasitized for language
uses and staged appropriately.
The bar-code analogy also helps one understand
why various attempts to measure this consensus might
succeed or fail. Were the representation a string in
time (as when the optical wand is swiped across the
bars), and the strings in various areas synchronized in
time, we might see the EEG from various regions
move up and down in synchrony (the EEG
coherence is a measure of this). But if the
strings were out of phase with one another (if I were
designing such a system, I'd do that to prevent out-of-control oscillations such as seizures), it might be much
harder to detect string consensus in various regions.
And if the representation were instead spatial (like the
bar code on the package), merely repeating in the
manner of wallpaper designs, we might require a very
sensitive imaging method to detect the consensus.
256 Oswald Spengler, The Decline of the
West (Knopf, 1926), vol. 1, p. 166 of the
abridged edition.
Chapter 10. Friday Harbor:
Is There Intelligent Life on Earth Yet?
258 Alison Jolly, "The evolution of purpose." In
Machiavellian Intelligence, edited by
Richard W. Byrne and Andrew Whiten
(Clarendon Press, 1988), pp. 363-378 at p. 378.
259 Chief Seattle, 1854, quoted from a U.S.
National Park Service exhibit in Seward, Alaska.
260 Alfred W. Crosby, Ecological Imperialism:
The Biological Expansion of Europe, 900-1900 (Cambridge University Press, 1986).
Role of disease, firearms in conquering virgin
continents.
269 Edwin Dobb, "The big picture." The
Sciences 29(2):44-50 (1989), at p. 49.
270 Gaia, alas, is only capable (at most) of keeping
things suitable for plants and simple animal life --
not intelligent life. See James Lovelock,
The Ages of Gaia (Norton, 1988).
272 Paul R. Ehrlich and Anne H. Ehrlich, The
Population Explosion (Simon and Schuster,
1990). "The critical prerequisites to reduced
fertility are five: adequate nutrition, proper
sanitation, basic health care, education of women,
and equal rights for women. The first four factors
reduce infant mortality, allowing a reasonable
expectation that a given child will survive to
adulthood. Female education is an especially
interesting and in some ways the most unexpected
finding. Women will apply even a few years of
schooling to improving life for their families by
providing more nutritious, balanced meals and
better home health care and sanitation...
Improving the home situation reduces infant and
child mortality, making men and women more
receptive to the idea of smaller families. And the
women's education makes them more open to
contraception and better able to employ it
properly. Finally, when women have sources of
status other than children, family size often
decreases."
272 Alas, those breakwaters exist no more, thanks to
an ill-conceived plan to double the width of the
Northwestern University campus by filling in the
lake. Inelegant riprap, a jumble of broken
concrete slabs representing the throw-away
building era, has replaced the sand beaches.
Northwestern has created a lagoon in the midst of
its landfill, though with the unmistakably uniform
contours created only by bulldozers. But the
outer strip of walkway between lagoon and lake
has some of the sense of the old breakwaters.
274 Jared Diamond, "The worst mistake in the
history of the human race", in Discover
(May 1987), p. 64 ff. See also Mark N. Cohen
and George J. Armalagos, editors, Paleo-
pathology at the Origins of Agriculture,
(Academic Press, 1984).
275 History of technological civilizations from a
lecture by Professor Jon Bridgman, University of
Washington (25 May 1989).
277 Paleo-Indians as searching for the source of the
aurora: This variant on "looking for the pot of
gold at the end of the rainbow" occurred to me
when I noticed that the magnetic pole was east
and north of the Mackenzie River delta, east of
those North Slope oil fields and wildlife refuges.
Indians in Siberia following the aurora would
have been led to the Bering Strait; once within
Alaska, they would have been led up north around
the mountains that, during the ice age, blocked
other routes east and south. And so they could
have discovered the Ice-free Corridor to Montana,
just by initially trying to find the most intense
"root" of the Northern Lights.
278 "Infiltration of mind into the universe...."
Freeman Dyson, Infinite in All
Directions (Harper and Row, 1988), p. 118.
278 "Gould's Principle...," see Stephen Jay Gould,
The Flamingo's Smile (Norton, 1985),
p. 401.
279 Norman Mailer, in accepting the 1969 National
Book Award for The Armies of the
Night.
280 Stephen H. Schneider, "The greenhouse effect:
science and policy." Science 243:771-781
(10 February 1989). And his book Global
Warming: Are We Entering the Greenhouse
Century? (Sierra Club Books, 1989). See the
"Managing Planet Earth" issue of Scientific
American (September 1989).
The illustration of the cold spikes in the North
Atlantic Ocean since the last interglaciation is adapted
from the Camp Century core (east of Thule, northern
Greenland) shown in Figure 4 of Dansgaard et al.
(1982). It is based on the oxygen isotope ratio; seen
in ocean floors, the slow trends in this ratio tend to
reflect ice volume (filtered by mixing times) but the
rapid changes from ice cores may be due to the
surface temperature of the North Atlantic Ocean at the
time of evaporation in the mid-latitudes (higher
temperatures aid in the "launch" of the heavier water
molecules containing the oxygen-18 isotope); this
water subsequently fell on northern Greenland as snow
and was compacted into ice layers. Rapid fluctuations
may also be influenced (e.g., Fairbanks 1989) by
surges of fresh water into the Atlantic from ice dams
breaking and draining huge lakes of meltwater via the
St. Lawrence River.
281 W. S. Broecker, letter in Science
245:451 (4 August 1989).
49 Simulations of North Atlantic Current's deep water
production: Uwe Mikolajewicz, Benjamin D.
Santer, and Ernst Maier-Reimer, "Ocean response
to greenhouse warming." Nature 345:589-593
(14 June 1990). This is only the first round of such
simulations of ocean-atmospheric linkage; successor
models will hopefully simulate the Current in more
detail and analyze its stability.
286 John Maynard Smith, Did Darwin Get It
Right? Essays on Games, Sex, and Evolution
(Chapman and Hall, 1988), p. 37.
289 Most governments are still treating scientific
research in the ocean-atmosphere systems as if it
were just another aspect of routine agricultural
research. Or of improving weather forecasting.
Hardly as serious a matter as, say, the perceived
need for yet-another new "defense" system, or
bailing out the Chrysler Corporation, or rescuing
the savings-and-loan-association gamblers. Those
examples from recent U.S. history involve
industries that, unlike science, contribute mightily
to politicians' campaign funds as a way of gaining
a hearing for their industry's problems. They may
not be able to buy solutions, but they can keep
their problems from getting placed on a back
burner via contributions and high-priced lobbyists.
And their problems are, relatively speaking, easily
comprehended. Getting the politicians' attention
is sometimes hard for scientific-based agendas,
given that the politicians are mostly lawyers who
avoided science courses in college, who think
mostly in terms of creating prohibitions rather
than plans, using penalties rather than
preparedness.
The illustration showing the end of the last glaciation,
as seen from northern Greenland (Camp Century) and
from Antarctica (Byrd Station) ice cores. Adapted
from Fig. 2 of the Broecker et al. (1985) review;
data from S. Johnsen, W. Dansgaard, H. Clausen,
and C. Langway, Nature 235:429-434 (1972).
The illustration of the Allerød-Dryas chattering, and
the speed of the end of the Younger Dryas, was
adapted from Fig. 1 of Dansgaard et al. (1989) and
utilizes the ice core at "Dye 3" in southern Greenland.
290 "Like an Old Testament god with lots of rules and
no mercy" is, I confess, what Joseph Campbell
said in his interview with Bill Moyers on Nova
(1988) -- but about personal computers, not
climate!
290 Another redirected characterization: I have
adapted the Conrad bad-weather-ahead tale from
that (this time regarding nuclear terrorism) by
Luther J. Carter, Nuclear Imperatives and
the Public Trust, excerpted in Issues in
Science and Technology (Winter 1987), p. 60.
291 A. E. Housman, lines 9-16 of "Smooth between
sea and land." In More Poems
(Knopf, 1936), p. 64.
The Author
William H. Calvin, Ph.D., is a neurophysiologist on the
faculty of the University of Washington in Seattle. During the
1960s and 1970s, his research interests were largely concerned
with how individual nerve cells function electrically. During
the 1980s, he became interested in the problems that overlap
neurobiology, anthropology, evolutionary biology, and
developmental biology -- especially the fourfold increase in the
brain size of hominids during the past 2.5 million years and
the attainment of language and plan-ahead consciousness.
The Ascent of Mind
(Bantam 1990) is my book on the
ice ages and how human intelligence evolved; the
"throwing theory" is one aspect.