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Resuming the Enlightenment
Quest
by Edward O. Wilson 
 onsilience, a term introduced by the
English theologian and polymath William Whewell in his 1840 masterwork
The Philosophy of the Inductive Sciences, means the alignment
(literally, the "jumping together") of knowledge from different
disciplines. Exotic as its origins sound, the idea is neither an abstruse
philosophical concept nor a mere plaything of intellectuals. It is the
mother's milk of the natural sciences.
Since Whewell's time,
physics, chemistry, and biology have been connected by a web of causal
explanation organized by induction-based theories that telescope into one
another. The entire known universe, from the smallest subatomic particles
to the reach of the farthest known galaxies, together spanning more than
40 orders of magnitude (a magnification of one followed by more than 40
zeros), is encompassed by consilient explanation. Thus, quantum theory
underlies atomic physics, which is the foundation of reagent chemistry and
its specialized offshoot biochemistry, which interlock with molecular
biology--essentially, the chemistry of organic macromolecules--and thence,
through successively higher levels of organization, cellular, organismic,
and evolutionary biology. This sequence of causal explanation proceeds
step by step from more general phenomena to the increasingly complex and
specific phenomena arising from them. Such is the unifying and highly
productive understanding of the world that has evolved in the natural
sciences. Its success testifies to a fortunate combination of three
circumstances: the surprising orderliness of the universe, the possible
intrinsic consilience of all knowledge concerning it, and the ingenuity of
the human mind in comprehending both.
On the horizon are the social
sciences and the humanities. Ever since the decline of the
Enlightenment in the late 18th century--and, with it, confidence in
the unity of knowledge--it has been customary to speak of these
second and third great branches of learning as intellectually
independent. They are separated, conventional wisdom has it, by an
epistemological discontinuity, in particular by possession of
different categories of truth, autonomous ways of knowing, and
languages largely untranslatable into those of the natural
sciences.
Now, however, the expansion of consilient
cause-and-effect explanation outward from the natural sciences
toward the social sciences and humanities is calling the traditional
division of knowledge into question. What most of the academy still
takes to be a discontinuity is starting to look like something
entirely different, a broad and largely unexplored terrain of
phenomena bound up with the material origins and functioning of the
human brain. The study of this terrain, rooted in biology, appears
increasingly available as a new foundational discipline of the
social sciences and humanities. The discontinuity, it now seems, is
neither an intrinsic barrier between the great branches of learning
nor a Hadrian's Wall protecting humanistic studies and high culture
from reductionistic barbarians, but rather a subject of
extraordinary potential awaiting cooperative exploration from both
sides.
At the heart of this borderland is the shifting
concept of culture and its hitherto puzzling relation to human
nature--and thence to the general inherited properties of individual
behavior. In the spirit of the natural sciences, the matter can be
expressed, I believe, as a problem to be solved. It is as follows:
Compelling evidence shows that all culture is learned. But its
invention and transmission are biased by innate properties of the
sensory system and the brain. These developmental biases, which we
collectively call human nature, are themselves prescribed by genes
that evolved or were sustained over hundreds of thousands of years
in primarily cultural settings. Hence, genes and culture have
coevolved; they are linked. What then, is the nature of gene-culture
coevolution, and how has it affected the human condition today?
That, in my opinion, is the central intellectual question of the
social sciences and humanities. It is also one of the most important
remaining problems of the natural sciences.
Confidence in the unity of knowledge--universal
consilience--rests ultimately on the hypothesis that all mental
activity is material in nature and occurs in a manner consistent
with the causal explanations of the natural sciences. During the
past several decades, that hypothesis has gained considerable
support from four disciplines that succeed partially in connecting
the great branches of learning. The first is cognitive neuroscience,
also known as the brain sciences--the once but no longer "quiet"
revolution of neuroscience--which is physically mapping the mental
process. The second is human behavioral genetics, now in the early
stages of teasing apart the hereditary basis of the process,
including the biasing influence of the genes on mental development.
The third bridging discipline is evolutionary biology (including
human sociobiology, often referred to as evolutionary psychology),
which attempts to reconstruct the evolution of brain and mind. The
last is environmental science, which describes the physical
environment to which humanity is genetically and culturally adapted.
|
The natural sciences are best
understood as humanity's way of correctly perceiving the real world,
as opposed to the way the human brain perceives that same world
unaided by instruments and verifiable fact and theory. The brain, it
is becoming increasingly clear, evolved as an instrument of
survival. It did not evolve as a device to understand itself, much
less the underlying principles of physics, chemistry, and biology.
Under the circumstances of physical environment and culture
prevailing from one generation to the next during the long haul of
prehistory, natural selection built a brain that conferred the
highest rates of survival and reproduction. The jury-rigged quality
of our perceptual and cognitive apparatus, the legacy of genetic
evolution, is part of the reason social scientists have such a hard
time grappling with human nature, why so much of the history of
philosophy can be fairly said to consist of failed models of the
brain, and why people generally understand automobiles better than
their own minds.
Consider the matter of vision. What we
intuitively believe to be the "real world" is what we see. But what
we see is only an infinitesimal slice of the electromagnetic
spectrum, comprising wavelengths of 400 to 700 billionths of a
meter. With instrumentation, we are now able to observe the
remainder of the spectrum that rains down on our bodies, from gamma
waves trillions of times shorter than visible light to radio waves
trillions of times longer. Many animals see a part of the spectrum
outside our range. Insects, for example, depend heavily on
ultraviolet light at wavelengths shorter than the human visible
spectrum. Color in the visible spectrum also deceives us. We
intuitively think that the rainbow is a natural phenomenon existing
apart from the human mind, but it is not. Its palette is a product
of the way the visual system and brain break the continuously
varying wavelength of sunlight into the seemingly discrete segments
we call colors. Such hereditary filtering and self-deception occur
in all of the other senses. And some capabilities present in other
organisms are totally absent from our uninstrumented minds. We have,
for example, no organs to monitor the electric fields that some
species of fish use to guide themselves through dark water, or the
magnetic field by which migratory birds navigate across clouded
night skies.
Why are human beings, supposedly the summum
bonum of creation, so handicapped? The simplest and most thoroughly
verifiable answer has been provided by the natural sciences, and
most particularly the borderland disciplines of cognitive
neuroscience and evolutionary biology. Outside our heads there is
freestanding reality. Only lunatics and a sprinkling of
constructivist philosophers doubt its existence. Inside our heads is
a reconstruction of reality based on sensory input and the
self-assembly of symbol-based concepts. Scenarios based on these
concepts, rather than an independent executive entity in the
brain--the "ghost in the machine," in philosopher Gilbert Ryle's
famous derogation--appear to constitute the mind. The scenarios of
conscious thought move constantly back and forth through time. As
these configurations fly by, driven by stimuli and drawing upon
memories of prior scenarios, they are weighted and guided by
emotion, which is the modification of neural activity that animates
and focuses mental activity. |
Emotion, as now understood, is not
something separate and distinct from thinking, as the Romantics
fancied. Rather, it is an active partner of ratiocination and a
crucial component of human thought. Emotion operates through
physiological processes that select certain streams of information
over others, shifting the body and mind to higher or lower degrees
of activity, agitating the neural circuits that create scenarios,
and selecting for ones that end in certain ways. The winning
scenarios, those that match goals preprogrammed by instinct and the
reinforcing satisfactions of prior experience, determine focus and
decision.
In this view, which represents a consensus of
many investigators in cognitive neuroscience, what we call
meaning is the linkage among the neural networks created by
the spreading excitation that enlarges imagery and engages emotion.
The competitive selection among scenarios is what we call
decision making. The outcome, in terms of the match of the
winning scenarios to instinctive or learned favorable states, sets
the kind and intensity of subsequent emotion. The self, by
virtue of the physical location of the brain in the body and the
programs of emotional response, is the necessary central player in
the scenarios. The persistent form and intensity of emotions is
called mood. The ability of the brain to generate novel
scenarios and settle upon the most effective among them is called
creativity. The persistent production of scenarios lacking
reality and survival value is called insanity.
The alignment of outer existence with its
inner representation has been distorted by the idiosyncrasies of
human evolution, the hundred-millennium process directed primarily
by the struggle to survive rather than the pursuit of
self-understanding. The brain, although a magnificent instrument, is
still rooted in the deep genetic history of the Paleolithic Age,
when most or all of human evolution occurred. Introspection alone
cannot disclose the sensory and psychophysiological distortions it
creates, which are usually beneficent but sometimes catastrophic. To
diagnose and correct the misalignment is the proper task of the
natural sciences and--one can reasonably hope--the social sciences
and humanities as well. To explore the borderland between the great
branches of learning would seem to lead to a better understanding of
the human condition than the various skeptical and relativistic
accounts of "socially constructed" realities supplied by
intellectuals who have lost faith in the original Enlightenment
quest for unified knowledge. |
Such of the new understanding will
hinge on an inquiry into the exact manner by which genetic evolution
and cultural evolution have been joined to create the mind. The key
to the linkage can be found in the properties of human nature. This
diagnostic core of Homo sapiens is not the genes, which prescribe
it, nor culture, which is its product. Human nature is the ensemble
of epigenetic rules of mental development, the hereditary
regularities in the growth of individual minds and behavior.
Following are some of the examples that researchers in the natural
and social sciences have identified, proceeding from the relatively
simple to the complex:
- The smile, which appears in infants from the ages of two to
four months, invariably evokes affection from adults and
reinforces bonding between caregiver and infant. In all cultures
and throughout life, smiling is used to signal friendliness,
approval, and a sense of pleasure. Each culture molds its meaning
into nuances determined by form and the context in which it is
displayed. There is no doubt that smiling is hereditary. It
appears on schedule in deaf-blind children and even in
thalidomide-deformed children who are not only deaf and blind but
crippled so badly they cannot touch their own faces.
- Phobias are aversions powerful enough to engage the autonomic
nervous system. They can evoke panic, cold sweat, and nausea; are
easily acquired, often from a single frightening experience; and
are notoriously difficult to eradicate. The most common phobias
are directed at the ancient perils of humankind, including snakes,
spiders, dogs (thus, wolves), heights, closed spaces, crowds of
strangers, and running water. They rarely focus on the far more
dangerous objects of modern life, such as automobiles, electric
sockets, knives, and firearms. It is reasonable to suppose that
such selective avoidance is an inherited predisposition that
reflects the long history of natural selection during which the
human brain formed. In other words, the ancient dangers are
"remembered" in the epigenetic programs, while the modern ones
have not existed long enough for aversions to them to be
hereditarily installed in the same manner.
- Color vision, one of the important sensory determinants of
culture, has been relatively well tracked all the way from genes
to neurons. The chemistry of the three protein cone pigments of
the retina, both the amino acids of which they are composed and
the shapes into which the molecular chains are folded, is fully
known. So is the sequence of base pairs in the genes on the
X-chromosome that prescribe them, as well as the sequence of the
mutations that cause color blindness, the triggering of the cone
neurons by light-induced changes in the pigments, the coding used
by the optic nerve to distinguish wavelength, and the pathways
leading from the optic nerve cells to the higher integrating
centers of the visual cortex in the rear of the brain.
By
inherited molecular processes, the human sensory and nervous systems
break continuously varying wavelengths of light into colors. We
perceive, in proceeding from the short-wavelength end to the
long-wavelength end of the spectrum, first a broad band of blue,
then green, then yellow, and finally red. The array is arbitrary in
an ultimately biological sense. That is, it is only one of many
arrays that might have evolved over the past millions of years. But
it is not arbitrary in a cultural sense. Having evolved genetically,
it cannot be altered by learning or by conscious internal
construction of new color codes.
All of culture involving color is derived
ultimately from these molecular and cellular processes. Color terms
independently invented by societies around the world are faithfully
clustered in the least ambiguous wavelength zones of the four
elementary colors. Cultures tend to avoid the ambiguous intermediate
zones. Each society uses from two to 11 basic linguistic terms drawn
from within the favored zones. The maximum 11 are black, white, red,
yellow, green, blue, brown, purple, pink, orange, and gray. At one
extreme, the Dani of New Guinea, for example, use only two of the
terms, and at the other extreme, English speakers use all 11. From
societies with simple classifications to those with complex
classifications, the combinations of basic color terms generally
grow in a hierarchical fashion, as follows:
Languages with two basic color terms
distinguish black and white.
Languages with three terms have words for
black, white, and red.
Languages with four terms have words for black,
white, red, and either green or yellow.
Languages with five terms have words for black,
white, red, green, and yellow.
Languages with six terms have words for black,
white, red, green, yellow, and blue.
Languages with seven terms have words for
black, white, red, green, yellow, blue, and brown.
No such precedence occurs among the remaining
four basic colors, purple, pink, orange, and gray, when these have
been added to the first seven.
If basic patterns were invented and combined at
random from the 11 basic colors, the vocabularies of different
societies would be drawn helter-skelter from among 2,036
mathematically possible combinations. The evidence indicates that,
on the contrary, they are drawn primarily from only 22. This
constraint can be reasonably interpreted as an epigenetic rule in
addition to that of color vision itself. Unlike those of basic color
vision, however, its genetic and neurobiological bases remain
unknown. |
Incest avoidance, the focus of so
many cultural conventions, also springs from a hereditary epigenetic
rule. The rule is called the Westermarck effect, after the Finnish
anthropologist Edward A. Westermarck, who first reported it in 1891.
Recent anthropological research has refined it as follows: when a
boy and girl are brought together before one or the other is 30
months of age, and then the pair are raised in proximity (they use
the same potty, so to speak), they are later devoid of sexual
interest in each other; indeed, the very thought of it arouses
aversion. This emotional incapacity, fortified in many societies by
a rational understanding of the consequence of inbreeding, has led
to the cultural incest taboos--whose origins Sigmund Freud explained
differently, and erroneously, as barriers against strong innate
urges to commit incest. The Darwinian advantage of the epigenetic
rule is overwhelming. The mortality rate among children born of
incest-mating of full siblings or parents and offspring--is about
twice that of outbred children, and among those who survive, genetic
defects such as dwarfism, heart deformities, deaf-mutism, and severe
mental retardation are 10 times more common. Human incest avoidance
is obedient to the following general rule in animals and plants:
almost all species vulnerable to moderate or severe inbreeding
depression use some biologically programmed method to avoid incest.
Homo sapiens not only conforms to this rule but does so in the same
manner as our closest evolutionary relatives. Among the apes,
monkeys, and other nonhuman primates, resistance to incest consists
of two barriers. In the first, young individuals of all 19 social
species whose mating patterns have been studied practice the
equivalent of human exogamy: before reaching full adult size, they
leave the group in which they were born and join another. The second
barrier is the Westermarck effect. In all species whose sexual
development has been carefully studied, including marmosets and
tamarins of South America, Asian macaques, baboons, and chimpanzees,
adults avoid mating with individuals who were intimately known to
them in early life. In as many as a third of human societies there
exists in addition a third, cultural barrier: incest is proscribed
due to the direct recognition that children with congenital
disabilities are a frequent product of incestuous unions. Thus, the
incest taboos and myths that pervade cultures everywhere appear
likely to have arisen from the Westermarck effect, but also, in a
minority of societies, from a direct perception of the destructive
effects of inbreeding.
Epigenetic rules, the true combinatorial
elements of human nature, evidently shape the development of mind
and social interaction through most, if not all, categories of
behavior. While the full causal sequences into which the rules fit,
which run from genes to cells to sensory organs to behavior to
culture, are still poorly understood, they appear clearly to be the
key link between the evolution of genes and the evolution of
culture.
The process of gene-culture coevolution itself
is also still in an early stage of research, but a broad outline of
the process in theory is possible. I believe the following account
represents a consensus of the small number of investigators working
on the subject.
Culture is created by the communal mind, this
view holds, and each mind in turn is the product of the genetically
structured human sensory system and brain. Genes and culture are
therefore inseparably linked. But the linkage is flexible, to a
degree still mostly unmeasured. The linkage is also tortuous: genes
prescribe epigenetic rules, which are the inherited neural pathways
and regularities in cognitive development by which the mind
assembles itself. The mind grows by learning those parts of the
environment and surrounding culture available to it. Mental
development is a selective absorption process, one that is
unavoidably biased by the epigenetic rules.
|
Is part of gene-culture
coevolution, culture is reconstructed collectively in the minds of
individuals each generation. When oral tradition is supplemented by
writing and the arts, it can grow indefinitely large (example: five
million patents to the present time in the United States alone), and
it can even skip generations. But the biasing influence of the
epigenetic rules, being genetic and ineradicable, remains the same
across all societies and generations.
The epigenetic rules nevertheless vary
genetically in degree among individuals within populations. Some
individuals have always inherited epigenetic rules in different
strengths from others, degrees of expression which, in past
evolutionary time at least, enabled them to survive and reproduce
better in the surrounding environment and culture. By this means,
over many generations, the more successful epigenetic rules spread,
along with the genes that prescribe them. As a consequence, the
human species has evolved by natural selection in the developmental
biases of mind and behavior, hence in human nature, just as it has
in the anatomy and physiology of the body.
To outline the theory of the coevolution of
genes and culture in this way is not to claim that particular forms
of culture are genetically determined. Certain cultural norms can
survive and reproduce better than others, even when guided by
exactly the same epigenetic biases as competing norms, causing
culture to evolve in a track parallel to and usually much faster
than genetic evolution. The quicker the pace of cultural evolution,
the weaker the connection between genes and culture, although the
connection is never completely broken. Culture allows a rapid
adjustment to changes in the environment by finely tuned adaptations
invented and transmitted without correspondingly precise, matching
genetic prescription. In this respect, human beings differ
fundamentally from all other animal species. Particular cultures can
also be maladaptive in the long term, causing the destruction of
individuals and societies that contrived them. But the linkage
between genes and culture is unbreakable; culture can never have a
life entirely on its own. Nor, I believe, should we wish it
otherwise. Human nature is what defines our species and binds it
together.
The consilient view of the human condition
that I have outlined only briefly here, and which I elaborate in
Consilience: The Unity of Knowledge, is predicated on the
well-supported assumption that Homo sapiens is a biological species,
having evolved for the most part in the same manner as the remainder
of life, and conservatively enough that the humanity-defining traits
of language and culture retain a residue of their deeper, genetic
history. While still very sketchy in detail, the emerging factual
picture of the epigenetic rules lends support to consilience and,
for the time being at least, to the theory of gene-culture
coevolution. It also suggests in broad outline an important part of
the terrain between the great branches of learning that can be
fruitfully explored. |
Such an extension of consilient
explanation from the natural sciences to the social sciences and
humanities may be faulted as reductionistic, and for that reason
unsuited to the hypercomplex realities of human social life. But
reductionism is the driving wedge of the natural sciences, by which
they have already broken apart many hypercomplex systems.
Reductionistic analysis typically proceeds from more complex and
specific phenomena and the disciplines addressing them to underlying
phenomena that are less complex and specific. For example, the
living cell has been opened to clear view by biochemistry and
molecular biology, and mental processes are beginning to yield to
cellular biology and neurophysiology. Both are among the
hypercomplex phenomena that have so far proved congenial to
consilient explanation, and both are directly relevant to human
social behavior. There is no obvious reason why the social sciences
and humanities, except by degree of their specificity and complexity
(and, granted, these are important distinctions), should prove
resistant to the same approach.
Moreover, the scientific method is equally
concerned with synthesis, and thereby holism. The most successful
research has always been cyclical. It begins with the description of
a complex entity or process. It proceeds by reduction to the main
components, then reassembly of the components in vitro or by
abstract modeling to the original whole, followed by correction
through testing, further reduction, and reassembly. And so on
around, until understanding is considered satisfactory by even the
most demanding critics.
It may be further argued that attempts at such
an extension are merely a return to the failed program of logical
positivism, a variation on general positivism that attempted to
define the essence of scientific statements by means of rigorous
logic and the analysis of language. But logical positivism, whose
influence peaked among philosophers from the 1920s to the early
1940s, lacked cognitive neuroscience, human genetics, evolutionary
biology, and environmental science. None of these bridging
disciplines were mature enough to shed light on the linkage between
biology and culture. Logical positivism was also argued from the top
down in a largely abstract framework. That is, its proponents set
out to identify freestanding criteria against which scientific
knowledge can be judged. Every symbol, they argued, should denote
something real. It should be consistent with the total structure of
established facts and theories, with no revelations or free-flight
generalizing allowed. Theory must follow in lockstep with facts,
during which process the informational content of language is
carefully distinguished from its emotional content. Finally,
verification, the logical positivists argued, is all-important;
scientific statements should clearly imply the methods and reasoning
used to verify the conclusions drawn. If these guidelines are
progressively refined and followed, they concluded, we can hope to
close in on objective truth.
The fatal flaw in logical positivism was in the
semantic linchpin of the system: its creators and followers could
not agree on the basic distinctions between fact and concept,
between generalization and mathematical truth, or between theory and
speculation. Stalled by the combination of these fog-shrouded
dichotomies, they were unable to arrive at an invariant and
fundamental difference between scientific and nonscientific
statements. |
The shortcoming of logical
positivism was ignorance of how the brain works, and why. That, in
my opinion, is the whole story. Neither philosophers nor scientists
who attacked the problem could explain the physical acts of
observation and reasoning in other than highly subjective terms.
None could track material phenomena of the outer world through the
labyrinth of causal processes in the inner mental world, and thus
precisely map outer material phenomena onto the inner material
phenomena of conscious activity. But there is every reason to
suppose that such a feat can be accomplished. Such is the means by
which symbols and concepts might in time be exactly defined, and
objective truth more precisely triangulated.
In short, the canonical criterion of objective
truth so ardently sought by the logical positivists is not a
philosophical problem, and it cannot be attained, as many had
expected, by logical and semantical analysis. It is an empirical
problem solvable only by a continuing investigation of the physical
basis of the mind itself. In time, like so many philosophical
searches of the past, it will be transformed into the description of
a material process.
Meanwhile, the search for universal consilience
begun in the Enlightenment is gaining in factual substance. The
borderland domain between the great branches of learning appears at
last to be coming into focus. If successful, its exploration offers
the prospect of a full disciplinary foundation of the social
sciences, by extending analysis to the deeper levels of biological
organization that underlie human behavior and the origins of
culture. By this means, I believe, can the social sciences expect to
create a true and more powerful body of theory. Through similar
explanatory connections to the natural sciences, the exploration of
aesthetics and the creative process offers a comparable foundation
for interpretation of the arts. And not least, consilient
explanation will shed much-needed new light on the material origins
of ethical precepts and religious belief.
Reprinted from the
Winter 1998 Wilson Quarterly .
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