4 - EDEN AS A METAPHOR: THE EVOLUTION OF MAN
Then wilt thou not be loth To leave this Paradise, but shalt possess A Paradise within thee,
happier far ... They hand in hand with wandering steps and slow Through Eden took
their solitary way. JOHN MILTON
Paradise Lost
Why didst thou leave the trodden paths of men Too soon, and with
weak hands though mighty heart Dare the unpastured dragon in his
den? Defenseless as thou wert, oh, where was then Wisdom, the
mirrored shield . . . ? PERCY BYSSHE SHELLEY
Adonais
FOR THEIR surface area, insects weigh very little. A beetle,
falling from a high altitude, quickly achieves terminal velocity:
air resistance prevents it from falling very fast, and, after
alighting on the ground, it will walk away, apparently none the
worse for the experience. The same is true of small
mammals-squirrels, say. A mouse can be dropped down a
thousand-foot mine shaft and, if the ground is soft, will arrive
dazed but essentially unhurt. In contrast, human beings are
characteristically maimed or killed by any fall of more than a
few dozen feet: because of our size, we weigh too much for our
surface area.
Therefore our arboreal ancestors had to pay attention.
Any error in brachiating from branch to branch could be fatal. Every
leap was an opportunity for evolution. Powerful selective forces
were at work to evolve organisms with grace and agility, accurate
binocular vision, versatile manipulative abilities, superb eye-hand
coordination, and an intuitive grasp of Newtonian gravitation. But
each of these skills required significant advances in the evolution
of the brains and particularly the neocortices of our ancestors.
Human intelligence is fundamentally indebted to the millions of
years our ancestors spent aloft in the trees.
And after we returned to the savannahs and abandoned the
trees, did we long for those great graceful leaps and ecstatic
moments of weightlessness in the shafts of sunlight of the
forest roof? Is the startle reflex of human infants today to
prevent falling from the treetops? Are our nighttime dreams of
flying and our daytime passion for flight, as exemplified in the
lives of Leonardo da Vinci or Konstantin Tsiolkovskii, nostalgic
reminiscences of those days gone by in the branches of the
high forest? *
* Modern rocket technology and space exploration owes an
incalculable debt to Dr. Robert H. Goddard, who through many decades
of devoted and lonely research was single-handedly responsible for
the development of essentially all important aspects of the modern
rocket. Goddard’s interest in this subject originated in a magic
moment. In the New England autumn of 1899, Goddard was a
seventeen-year-old high school sophomore who had climbed a cherry
tree and, while idly looking down at the ground around him,
experienced a kind of epiphanal vision of a vehicle that would
transport human beings to the planet Mars. He resolved to devote
himself to the task. Exactly one year later, he climbed the tree
again, and on every October 19th for the rest of his life, made a
special point of recollecting that moment. Can it be an accident
that this vision of voyages to the planets, which has led directly
to its own historical fulfillment, was glimpsed in the limbs of a
tree?
Other mammals, even other nonprimate and non-cetacean mammals, have
neocortices. But in the evolutionary line leading to man, when was
the first large-scale development of the neocortex? While none of
our simian ancestors are still around, this question can
nevertheless be answered or at least approached: we can examine
fossil skulls. In humans, in apes and monkeys, and in other mammals,
the brain volume almost fills the skull. This is not true, for
example, in fish. Thus by taking a cast of a skull, we can determine
what is called the endocranial volume of our immediate ancestors and
collateral relatives and can make some rough estimates of their
brain volumes.
The question of who was and who was not an ancestor of man
is still being hotly debated by the paleontologists, and hardly a
year goes by without the discovery of some fossil of
remarkably human aspect -much-older- than anyone had
previously thought possible. What seems certain is that about
five million years ago, there was an abundance of apelike animals,
the gracile Australopithecines, who walked on two feet and had brain
volumes of about 500 cubic centimeters, some 100 cc more than the
brain of a modern chimpanzee. With this evidence, paleontologists
have deduced that “bipedalism preceded encephalization,” by which
they mean that our ancestors walked on two legs before they evolved
big brains.
By three million years ago, there was a variety of bipedal
fellows with a wide range of cranial volumes, some considerably
larger than the East African gracile Australopithecines of a few
million years earlier. One of them, which L. S. B. Leakey, the
Anglo-Kenyan student of early man, called Homo habilis, had a brain
volume of about 700 cubic centimeters. We also have archaeological
evidence that Homo habilis made tools. The idea that tools are both
the cause and the effect of walking on two legs, which frees the
hands, was first advanced by Charles Darwin. The fact that these
significant changes in behavior are accompanied by equally
significant changes in brain volume does not prove that the one is
caused by the other; but our previous discussion makes such a casual
link appear very likely.
The table on page 92 summarizes the fossil evidence, through 1976,
on our most recent ancestors and collateral relatives. The two
rather different kinds of Australopithecines were not of the genus
Homo, not human; they were still incompletely bipedal and had brain
masses only about a third the size of the average adult human brain
today. Were we to meet an Australopithecine, say, on the subway, we
would perhaps be struck most by the almost total absence of
forehead. He was the lowest of lowbrows. There are significant
differences between the two kinds of Australopithecines.
The robust
species was taller and heavier, with most impressive “nut-cracker”
teeth and a remarkable evolutionary stability. The endocranial
volume of A. robustus varies very little from specimen to specimen
over millions of years of time. The gracile Australopithecines,
judging again from their teeth, probably ate meat as well as
vegetables. They were smaller and lither, as their name indicates.
However, they are considerably older and have much more variance in
endocranial volume than their robust cousins.
But, most important,
the gracile Australopithecine sites are associated with a clear
industry: the manufacture of tools made of stone and animal bones,
horns and teeth-painstakingly carved, broken, rubbed and polished to
make chipping, flaking, pounding and cutting tools. No tools have
been associated with A. robustus. The ratio of brain weight to body
weight is almost twice as large for the gracile as for the robust
Australopithecus, and it is a natural speculation to wonder whether
that factor of two is the difference between tools and no tools.
At apparently the same epoch as the emergence of
Australopithecus robustus, there arose a new animal, Homo habilis, the first true man. He was larger, both in body and in
brain weight, than either of the Australopithecines, and had a
ratio of brain to body weight about the same as that of the
gracile Australopithecines. He emerged at a time when, for
climatic reasons, the forests were receding. Homo habilis
inhabited the vast African savannahs, an extremely challenging
environment filled with an enormous variety of predators and
prey. On these plains of low grass appeared both the first
modern man and the first modern horse. They were almost exact
contemporaries.
In the last sixty million years, there has been a continuous
evolution of ungulates, well recorded in the fossil record, and
eventually culminating in the modern horse. Eohippus, the “dawn
horse” of some fifty million years ago, was about the size of an
English collie, with a brain volume of about twenty-five cubic
centimeters, and a ratio of brain to body weight about half that of
comparable contemporary mammals.
Since then, horses have experienced
a dramatic evolution in both absolute and relative brain size, with
major developments in the neocortex and particularly in the frontal
lobes - an evolution certainly accompanied by major improvements in
equine intelligence. I wonder if the parallel developments in the
intelligence of horse and man might have a common cause. Did horses,
for example, have to be swift of foot, acute of sense, and
intelligent to elude predators which hunted primate as well as
equine prey?
H. habilis had a high forehead, suggesting a significant development
of the neocortical areas in the frontal and temporal lobes as well
as the regions in the brain, to be discussed later, that seem to be
connected with the power of speech. Were we to encounter Homo habilis - dressed, let us say, in the latest fashion on the boulevards
of some modern metropolis - we would probably give him only a passing
glance, and that because of his relatively small stature. Associated
with Homo habilis are a variety of tools of considerable
sophistication. In addition, there is evidence from various circular
arrangements of stones that Homo habilis may have constructed
dwellings; that long before the Pleistocene Ice Ages, long before
men regularly inhabited caves, H. habilis was constructing homes
out-of-doors-probably of wood, wattle, grass and stone.
Since H. habilis and A. robustus emerged at the same time, it is
very unlikely that one was the ancestor of the other. The gracile Australopithecines
were also contemporaries of Homo habilis but much more ancient. It is therefore possible-although
by no means certain - that both H. habilis, with a promising
evolutionary future, and A. robustus, an evolutionary dead end,
arose from the gracile A. africanus, who survived long enough to be
their contemporary.
The first man whose endocranial volume overlaps that of modern
humans is Homo erectus. For many years the principal specimens of H.
erectus were known from China and thought to be about half a million
years old. But in 1976 Richard Leakey of the National Museums of
Kenya reported a nearly complete skull of Homo erectus found in
geological strata one and a half million years old. Since the
Chinese specimens of Homo erectus are clearly associated with the
remains of campfires, it is possible that our ancestors domesticated
fire much more than one half million years ago -which makes
Prometheus far older than many had thought.
Perhaps the most striking aspect of the archaeological record
concerning tools is that as soon as they appear at all they appear
in enormous abundance. It looks very much as though an inspired
gracile Australopithecine discovered for the first time the use of
tools and immediately taught the tool-making skill to his relatives
and friends. There is no way to explain the discontinuous appearance
of stone tools unless the Australopithecines had educational
institutions. There must have been some sort of stonecraft guild
passing on from generation to generation the precious knowledge
about the fabrication and use of tools-knowledge that would
eventually propel such feeble and almost defenseless primates into
domination of the planet Earth. Whether the genus Homo independently
invented tools or borrowed the discovery from the genus
Australopithecus is not known.
We see from the table that the ratio of body to brain weight is,
within the variance of measurement, roughly the same for the gracile
Australopithecines, Homo habilis, Homo erectus and modern humans.
The advances we have made in the last few million years cannot
therefore be explained by the ratio of brain to body mass, but
rather by increasing total brain mass, improved specialization of
new function and complexity within the brain,
and-especially-extrasomatic learning.
L. S. B. Leakey emphasized that the fossil record of a few million
years ago is replete with a great variety of manlike forms, an
interesting number of which are found with holes or fractures in
their skulls. Some of these injuries may have been inflicted by
leopards or hyenas; but Leakey and the South African anatomist
Raymond Dart believed that many of them were inflicted by our
ancestors. In Pliocene/Pleistocene times there was almost certainly
a vigorous competition among many manlike forms, of which only one
line survived-the tool experts, the line that led to us. What role
killing played in that competition remains an open question.
The gracile Australopithecines were erect, agile, fleet and three and a
half feet tall: “little people.” I sometimes wonder whether our
myths about gnomes, trolls, giants and dwarfs could possibly be a
genetic or cultural memory of those times. At the same time that the
hominid cranial volume was undergoing its spectacular increase,
there was another striking change in human anatomy; as the British
anatomist Sir Wilfred Le Gros Clark of Oxford University has
observed, there was a wholesale reshaping of the human pelvis. This
was very likely an adaptation to permit the live birth of the latest
model large-brained babies.
Today, it is unlikely that any further
substantial enlargement of the pelvic girdle in the region of the
birth canal is possible without severely impairing the ability of
women to walk efficiently. (At birth, girls already have a
significantly larger pelvis and skeletal pelvic opening than do
boys; another large increment in the size of the female pelvis
occurs at puberty.) The parallel emergence of these two evolutionary
events illustrates nicely how natural selection works.
Those mothers
with hereditary large pelvises were able to bear large-brained
babies who because of their superior intelligence were able to
compete successfully in adulthood with the smaller-brained offspring
of mothers with smaller pelvises. He who had a stone axe was more
likely to win a vigorous difference of opinion in Pleistocene times.
More important, he was a more successful hunter. But the invention
and continued manufacture of stone axes required larger brain
volumes.
So far as I know, childbirth is generally painful in only one of the
millions of species on Earth: human beings. This must be a
consequence of the recent and continuing increase in cranial volume.
Modem men and women have braincases twice the volume of Homo habilis’. Childbirth is painful because the evolution of the human
skull has been spectacularly fast and recent.
The American anatomist
C. Judson Herrick described the development of the neocortex in the
following terms:
“Its explosive growth late in phylogeny is one of
the most dramatic cases of evolutionary transformation known to
comparative anatomy.”
The incomplete closure of the skull at birth,
the fontanelle, is very likely an imperfect accommodation to this
recent brain evolution.
The connection between the evolution of intelligence and the
pain of childbirth seems unexpectedly to be made in the Book
of Genesis. In punishment for eating the fruit of the tree of the
knowledge of good and evil, God says to Eve,* “In pain shalt
thou bring forth children” (Genesis 3:16).
It is interesting that it
is not the getting of any sort of knowledge that God has
forbidden, but, specifically, the knowledge of the difference
between good and evil-that is, abstract and moral judgments,
which, if they reside anywhere, reside in the neocortex.
Even
at the time that the Eden story was written, the development of
cognitive skills was seen as endowing man with godlike powers
and awesome responsibilities. God says: “Behold, the man is
become as one of us, to know good and evil; and now, lest he
put forth his hand, and take also of the Tree of Life, and eat,
and live forever” (Genesis 3:22), he must be driven out of the
Garden. God places cherubim with a flaming sword east of Eden
to guard the Tree of Life from the ambitions of man.+
* God’s judgment on the serpent is that henceforth “upon thy belly shalt thou go”-implying that previously reptiles traveled by an
alternative mode of locomotion. This is, of course, precisely true:
snakes have evolved from four-legged reptilian ancestors resembling
dragons. Many snakes still retain anatomical vestiges of the limbs
of their ancestors.
+ Cherubim is plural; Genesis 3:24 specifies one flaming sword.
Presumably flaming swords were in short supply.
Perhaps the Garden of Eden is not so different from Earth as it
appeared to our ancestors of some three or four million years ago,
during a legendary golden age when the genus Homo was perfectly
interwoven with the other beasts and vegetables. After the exile
from Eden we find, in the biblical account, mankind condemned to
death; hard work; clothing and modesty as preventatives of sexual
stimulation; the dominance of men over women; the domestication of
plants (Cain); the domestication of animals (Abel); and murder (Cain
plus Abel).
These all correspond reasonably well to the historical
and archaeological evidence. In the Eden metaphor, there is no
evidence of murder before the Fall. But those fractured skulls of
bipeds not on the evolutionary line to man may be evidence that our
ancestors killed, even in Eden, many manlike animals.
Civilization develops not from Abel, but from Cain the murderer. The
very word “civilization” derives from the Latin word for city. It is
the leisure time, community organization and specialization of labor
in the first cities that permitted the emergence of the arts and
technologies we think of as the hallmarks of civilizations.
The
first city, according to Genesis, was constructed by Cain, the
inventor of agriculture-a technology that requires a fixed abode.
And it is his descendants, the sons of Lamech, who invent both
“artifices in brass and iron” and musical instruments. Metallurgy
and music-technology and art-are in the line from Cain. And the
passions that lead to murder do not abate: Lamech says,
“For I have
slain a man for wounding me, and a young man for bruising me; if
Cain shall be avenged sevenfold, truly Lamech seventy and
sevenfold.”
The connection between murder and invention has been
with us ever since. Both derive from agriculture and civilization.
One of the earliest consequences of the anticipatory skills that
accompanied the evolution of the prefrontal lobes must have
been the awareness of death. Man is probably the only
organism on Earth with a relatively clear view of the
inevitability of his own end. Burial ceremonies that include the
interment of food and artifacts along with the deceased go back at
least to the times of our Neanderthal cousins, suggesting not only a
widespread awareness of death but also an already developed ritual
ceremony to sustain the deceased in the afterlife.
It is not that
death was absent before the spectacular growth of the neocortex,
before the exile from Eden; it is only that, until then, no one had
ever noticed that death would be his destiny.
The fall from Eden seems to be an appropriate metaphor for some of
the major biological events in recent human evolution. This may
account for its popularity.* It is not so remarkable as to require
us to believe in a kind of biological memory of ancient historical
events, but it does seem to me close enough to risk at least raising
the question. The only repository of such a biological memory is, of
course, the genetic code.
* In the West. There are, of course, many insightful and profound
myths on the origin of mankind in other human cultures.
By fifty-five million years ago, in the Eocene Period, there was a
great proliferation of primates, both arboreal and ground-dwelling,
and the evolution of a line of descent that eventually led to Man.
Some primates of those times-e. g., a prosimian called
Tetonius-exhibit in their endocranial casts tiny nubs where the
frontal lobes will later evolve. The first fossil evidence of a
brain of even vaguely human aspects dates back to eighteen million
years to the Miocene Period, when an anthropoid ape which we call
Proconsul or Dryo-pithecus appeared. Proconsul was quadrupedal and
arboreal, probably ancestral to the present great apes and possibly
to Homo sapiens as well. He is roughly what we might expect for a
common ancestor of apes and men. (His approximate contemporary,
Ramapithecus, is thought by some anthropologists to be ancestral to
man.) Proconsul’s endocranial casts show recognizable frontal lobes
but much less well developed neocortical convolutions than are
displayed by apes and men today. His cranial volume was still very
small.
The biggest burst of evolution in cranial volume occurred in the
last few million years.
Patients who have had prefrontal lobotomies have been described as
losing a “continuing sense of self” - the feeling that I am a
particular individual with some control over my life and
circumstances, the “me-ness” of me, the uniqueness of the
individual. It is possible that lower mammals and reptiles, lacking
extensive frontal lobes, also lack this sense, real or illusory, of
individuality and free will, which is so characteristically human
and which may first have been experienced dimly by Proconsul.
The development of human culture and the evolution of those
physiological traits we consider characteristically human most
likely proceeded-almost literally-hand in hand: the better our
genetic predispositions for running, communicating and manipulating,
the more likely we were to develop effective tools and hunting
strategies; the more adaptive our tools and hunting strategies, the
more likely it was that our characteristic genetic endowments would
survive. The American anthropologist Sherwood Wash - burn of the
University of California, a principal exponent of this view, has
said:
“Much of what we think of as human evolved long after the use
of tools. It is probably more correct to think of much of our
structure as the result of culture than it is to think of men
anatomically like ourselves slowly developing culture.”
Some students of human evolution believe that part of the
selection pressure behind this enormous burst in brain
evolution was in the motor cortex and not at first in the
neocortical regions responsible for cognitive processes. They
stress the remarkable abilities of human beings to throw
projectiles accurately, to move gracefully, and-as Louis Leakey
enjoyed illustrating by direct demonstration-naked, to outrun
and immobilize game animals. Such sports as baseball, football,
wrestling, track and field events, chess and warfare may owe
their appeal-as well as their largely male following-to these prewired hunting skills, which served us so well for millions of
years of human history but which find diminished practical
applications today.
Effective defense against predators and the hunting of game were
both necessarily cooperative ventures. The environment in which man
evolved-in Africa in Pliocene and Pleistocene times-was inhabited by
a variety of terrifying mammalian carnivores, perhaps the most
awesome of which were packs of large hyenas. It was very difficult
to defend oneself alone against such a pack. Stalking large animals,
either solitary beasts or herds, is dangerous; some gestural
communication among the hunters is necessary.
We know, for example,
that shortly after man entered North America, via the Bering Straits
in the Pleistocene Period, there were massive and spectacular kills
of large game animals, often by driving them over cliffs. In order
to stalk a single wildebeest or stampede a herd of antelope to their
deaths, hunters must share at least a minimal symbolic language.
Adam’s first act was linguistic-long before the Fall and even before
the creation of Eve: he named the animals of Eden.
Some forms of gestural symbolic language, of course,
originated much earlier than the primates; canines and many
other mammals who form dominance hierarchies may indicate
submission by averting the eyes or baring the neck. We have
mentioned other submissive rituals in primates such as
macaques. The human greetings of bow, nod and curtsy may
have a similar origin. Many animals seem to signal friendship by
biting, but not hard enough to hurt, as if to say, “I am able to
bite you but choose not to do so.” The raising of the right hand
as a symbol of greeting among humans has precisely the same
significance: “I could attack you with a weapon but choose not
to wield one.” *
* The upraised and open right hand is sometimes described as a
“universal” symbol of good will. It at least runs the gamut from
Praetorian Guards to Sioux scouts. Since those wielding weapons are,
in human history, characteristically male, it should be and is a
characteristically male greeting. For these reasons, among others,
the plaque aboard the Pioneer 10
spacecraft-the first artifact of mankind to leave the solar
system-included a drawing of a naked man and woman, the man’s hand
raised, palm out, in greeting (see illustration on p. 246). In The
Cosmic Connection I describe the humans on the plaque as the most
obscure part of the message. Nevertheless, I wonder. Could the
significance of the man’s gesture be deduced by beings with very
different biologies?
Extensive gestural languages were employed by many human hunting
communities-for example, among the Plains Indians, who also used
smoke signals. According to Homer, the victory of the Hellenes at
Troy was conveyed from Ilium to Greece, a distance of some hundred
miles, by a series of signal fires. The date was about 1100 B.C.
However, both the repertoire of ideas and the speed with which ideas
can be communicated in gestural or sign languages is limited. Darwin
pointed out that gestural languages cannot usefully be employed
while our hands are otherwise occupied, or at night, or when our
view of the hands is obstructed. One can imagine gestural languages
being gradually supplemented and then supplanted by verbal languages
-which originally may have been onomatopoeic (that is, imitative in
sound of the object or action being described).
Children call dogs
“bow-wows.” In almost all human languages the child’s word for
“mother” seems imitative of the sound made inadvertently while
feeding at the breast. But all of this could not have occurred
without a restructuring of the brain.
We know from skeletal remains associated with early man that our
ancestors were hunters. We know enough about the hunting of large
animals to realize that some language is required for cooperative
stalking. But ideas on the antiquity of language have received a
measure of unexpected support from detailed studies of fossil
endocasts made by the American anthropologist Ralph L. Holloway of
Columbia University.
Holloway’s casts of fossil skulls are made of rubber latex, and
he has attempted to deduce something of the detailed
morphology of the brain from the shape of the skull. The
activity is a kind of phrenology, but on the inside rather than on
the outside and much more soundly based. Holloway believes
that a region of the brain known as Broca’s area, one of several
centers required for speech, can be detected in fossil endocasts;
and that he has found evidence for Broca’s area in a Homo habilis
fossil more than two million years old. The development of language,
tools and culture may have occurred roughly simultaneously.
There were, incidentally, manlike creatures who lived only a few
tens of thousands of years ago - the Neanderthals and the
Cro-Magnons — who had average brain volumes of about 1,500 cubic
centimeters; that is, more than a hundred cubic centimeters larger
than ours. Most anthropologists guess that we are not descended from
Neanderthals and may not be from Cro-Magnons either. But their
existence raises the question:
Who were those fellows? What were their accomplishments? Cro-Magnon
was also very large: some specimens were well over six feet tall. We
have seen that a difference in brain volume of 100 cubic centimeters
does not seem to be significant, and perhaps they were no smarter
than we or our immediate ancestors; or perhaps they had other, still
unknown, physical impediments.
Neanderthal was a lowbrow, but his
head was long, front to back; in contrast, our heads are not so
deep, but they are taller: we can certainly be described as
highbrows. Might the brain growth exhibited by Neanderthal man have
been in the parietal and occipital lobes, and the major brain growth
of our ancestors in the frontal and temporal lobes? Is it possible
that the Neanderthals developed quite a different mentality than
ours, and that our superior linguistic and anticipatory skills
enabled us to destroy utterly our husky and intelligent cousins?
So far as we know, nothing like human intelligence appeared on
Earth before a few million, or at least a few tens of millions of
years ago. But that is a few tenths of a percent of the age of
Earth, very late in December in the Cosmic Calendar. Why did it
appear so late? The answer clearly seems to be that some
particular property of higher primate and cetacean brains did
not evolve until recently. But what is that property? I can
suggest at least four possibilities, all of which have already
been mentioned, either explicitly or implicitly:
(1) Never before
was there a brain so massive;
(2) Never before was there a
brain with so large a ratio of brain to body mass;
(3) Never before
was there a brain with certain functional units (large frontal and
temporal lobes, for example);
(4) Never before was there a brain
with so many neural connections or synapses.
(There seems to be some
evidence that along with the evolution of the human brain there may
have been an increase in the number of connections of each neuron
with its neighbor, and in the number of microcircuits.)
Explanations
1, 2 and 4 argue that a quantitative change produced a qualitative
change. It does not seem to me that a crisp choice among these four
alternatives can be made at the present time, and I suspect that the
truth will actually embrace most or all of these possibilities.
The British student of human evolution
Sir Arthur Keith proposed
what he called a “Rubicon” in the evolution of the human brain. He
thought that at the brain volume of Homo erectus - about 750 cubic
centimeters, roughly the engine displacement of a fast motorcycle
- the uniquely human qualities begin to emerge. The “Rubicon” might,
of course, have been more qualitative than quantitative. Perhaps the
difference was not so much an additional 200 cubic centimeters as
some specific developments in the frontal, temporal and parietal
lobes which provided us with analytical ability, foresight and
anxiety.
While we can debate what the “Rubicon” corresponds to, the idea of
some sort of Rubicon is not without value. But if there is a Rubicon
anywhere near 750 cubic centimeters, while differences of the order
of 100 or 200 cubic centimeters do not-at any rate to us-seem to be
compelling determinants of intelligence, might not the apes be
intelligent in some recognizably human sense? A typical chimpanzee
brain volume is 400 cubic centimeters; a lowland gorilla’s, 500 cc.
This is the range of brain volumes among the tool-using gracile Australopithecines.
The Jewish historian Josephus added to the list of penalties and
tribulations that accompanied Mankind’s exile from Eden the loss of
our ability to communicate with the animals.
Chimpanzees have large brains; they have well-developed
neocortices; they, too, have long childhoods and extended periods of
plasticity. Are they capable of abstract thought? If they’re smart,
why don’t they talk?
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