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CC Preceptor Notes – 25
DARWIN
Darwin’s Role in CC
There’s a genuine question about how Darwin fits into CC. His most important
work – the Origin (O) – doesn’t tell us anything about moral or political issues:
indeed, it deliberately contains exactly one (promissory) reference to our species.
Of course, O is a wonderful work of science, one of the few (perhaps the only)
scientific text articulating a major idea that can be read by students outside the
sciences, and, interestingly, it’s probably the only founding historical work that is
still studied by practitioners in the field it founded. Additionally, it’s great for
reflecting on the methods of the sciences, since Darwin had to combat views
about scientific investigation that would have made any inquiry into the history of
life suspect. Is that enough to spend time on Darwin?
I don’t think so. Although I recommend discussing with your students the central
ideas of the theory of evolution by natural selection, and also talking about the
ways in which we can gain knowledge of the remote past, it’s also a good idea to
connect Darwin to the central themes that have emerged in many of the texts we
read. This is an occasion for probing the relations between science and religion,
and for considering whether Darwin destroyed the idea of a providence that
orders the world and its history. You can also explore his proposals in the
Descent of Man (D), looking at the accounts he offers of human sociality and
human morality. Darwin’s influence on social thought is well worth some time.
Although your students are likely to be appalled by some nineteenth century
applications (the construction of a hierarchy of races or the manifestoes for
competitive capitalism), many of them take current trends in evolutionary
psychology very seriously. Unfortunately, our new Broadview reader doesn’t
represent these issues very well; the Norton volume (edited by Appleton) is far
better in this respect, and you might want to make copies of some of the short
extracts from that.
Historical Background
Darwin’s life is a mixture of the banal and the mysterious, and it has generated
plenty of historical discussion. Born in 1809 to an upper-class family, he spent a
relatively quiet childhood, exploring, when he could, the Shropshire countryside
and its plants and animals. The Autobiography (written for his children)
suggests that he was considered a “rather ordinary boy”, and he certainly didn’t
stand out as an intellectual prodigy. Sent to Edinburgh at 16, he was supposed
to study medicine, but this proved unsatisfactory. After a short period of
classical cramming, Darwin was admitted to Christ’s College, Cambridge, where,
it was planned, he would study for the Church. This plan, too, went awry, and
Darwin’s Cambridge years were principally spent on expeditions in natural
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history; he became acquainted with the Professor of Geology (Adam Sedgwick).
Darwin’s principal mentor, however, was John Henslow, the Professor of Botany.
On leaving Cambridge, Darwin accompanied Sedgwick on a geological
expedition to Wales, and, returning from this, received a letter from Henslow,
which opened the possibility of joining the survey ship, H.M.S Beagle, as part
naturalist, part companion to the Captain, Robert Fitzroy. Darwin’s father
agreed to the idea, and Darwin embarked in 1831, returning in 1836. The
observations on the voyage changed Darwin’s ideas about the history of life, but
also furnished material for a number of papers on geological topics.
After returning to England, Darwin settled in London and became part of the
various scientific groups. In 1839, he married his cousin, Emma Wedgwood,
and, three years later, apparently for reasons of health, the couple moved to
Down in Kent, a small village not far from London; the move enabled Darwin to
enjoy the advantages of a reclusive invalid, particularly to dedicate himself to
developing his ideas about the history of life. During the 1840s, he began to
write about these ideas to his closest friends – as he wrote to Joseph Dalton
Hooker, he had been contemplating the transformation of species (“It is like
confessing a murder”).
In 1842, the anonymous publication of Vestiges of the Natural History of Creation
(which turned out to be by Robert Chambers, of Encyclopedia fame) prompted a
storm of negative reviews (Sedgwick wrote over 400 pages in denouncing it).
Chambers developed a relatively crude form of evolutionary account, and his
critics had plenty of opportunities for attack. Yet it was extremely influential –
not only did it sell far more copies than Darwin’s Origin (even by the late decades
of the nineteenth century) but also prompted Tennyson’s anguished In
Memoriam. The reception of Chambers’ work probably increased Darwin’s own
caution. At work on a big book, tentatively entitled Natural Selection, he would
share his subversive ideas with close friends – first Hooker, and later Charles
Lyell, Thomas Henry Huxley, and the Harvard botanist, Asa Gray – but he was
reluctant to publish. During the 1850s, he lavished considerable time on a
monograph on the taxonomy of barnacles.
In 1858, Darwin received a letter from a naturalist-traveler, Alfred Russel
Wallace, who, in a bout of malaria in the East Indies, had formulated a thesis of
evolution by natural selection. Darwin was crushed, believing that his tardiness
would now deprive him of all the credit for an idea that he had been refining for at
least fifteen years. Negotiations with Lyell led to a way out of the perceived
crisis. It was arranged that there should be a session of the Linnean Society,
one of the most prestigious London groups, at which Wallace’s essay should be
read, along with a paper by Darwin. The session took place, without any
particular sense of an event of great importance – indeed, the retiring President
of the Society lamented that the year 1858 hadn’t been notable for any great
discoveries. Darwin immediately went to work, distilling the ideas of Natural
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Selection into what he thought of as an “abstract”. It was published in 1859, as
On the Origin of Species by Means of Natural Selection.
Many, but not all, of the reviews were negative. But Darwin, pleading sickness,
had assembled a group of champions, most notably Huxley (“Darwin’s bulldog”)
who rode into the lists on his behalf. One famous incident was the special
session at the meetings of the British Association for the Advancement of
Science, where a packed hall listened to a debate between the Bishop of Oxford,
Samuel (“Soapy Sam”) Wilberforce and Huxley. In the hall, Robert Fitzroy, now
on the verge of insanity (or beyond) stalked around with a copy of the Bible,
intoning, “The Book! The Book!”. According to tradition, at the denouement of
the debate, Wilberforce is supposed to have turned to Huxley, and asked him
whether he claimed descent from the apes on his grandfather’s or on his
grandmother’s side; Huxley allegedly muttered, under his breath, “The Lord has
delivered him into my hands”, and responded by avowing that he would prefer to
claim kinship with the apes rather than to twist the scriptures to dishonest
purposes.
By 1867, Darwin and Huxley were confident that they had won the day for one
part of the theory of O: within the English-speaking world, as well as in Germany
and Russia, biologists were largely prepared to accept the idea that all living
organisms are connected by a process of descent with modification. Much more
controversial was the thesis that natural selection had been the principal agent of
evolutionary change, and, through the late nineteenth century, biologists
committed to evolution (descent with modification) explored alternative
mechanisms. Darwin himself allowed for other causes of evolutionary change,
and these become more widely used in later editions of O; precisely because
those editions are more hedged and qualified, it’s much better to read the first
edition. The nadir in the fortunes of natural selection came in the first decades
of the twentieth century, and it was only with the development of a synthesis
between Darwin’s account of natural selection and ideas about genetics
stemming from Mendel that what we think of as Darwinism was forged.
Darwin went on to write more specifically about human evolution in D, published
in 1871, and thereafter, to explore issues in the biology of emotions and, more
curiously, on the movement of soil by earthworms. At his death in 1882 he had
become revered as a great scientist, and there was a public demand that he be
buried in Westminster Abbey. His family would have preferred to inter him in the
churchyard at Down, but they acceded to the pressure, and, in a forceful eulogy,
the Dean of St. Paul’s Cathedral declared that, although Mr. Darwin’s ideas had
initially seemed at odds with the doctrines of Christianity, a more searching
examination had shown that this was not so. The Church of England had made
its peace with Darwin.
It seems fairly clear that Darwin himself didn’t accept this compatibilist line, and
his Autobiography records the lapse of his faith under the continued
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contemplation of the evolutionary view of life – he has become an agnostic (Aut.
94). Many scholars have thought that his published works carefully skirted the
troubling issues of religion out of consideration for the sensibility of his wife,
Emma, who seems to have been a faithful Christian. The Autobiography is also
sad in its depiction of his own intellectual and cultural development, and Darwin
records how he has lost his taste, once strong, for Shakespeare and other
poetry: “My mind seems to have become a kind of machine for grinding general
laws out of large collections of facts …” (Aut. 139). His self-portrait is regretful,
rather than consoling.
The Theory in its Context
Darwin gets blamed for a lot. Henry Morris, a long-time leader of the Institute for
Creation Research, asks the question “Which nineteenth century thinker had the
most evil influence on the twentieth century?”. You’d think there are some pretty
good competitors – Marx (father of communism and someone who sees religion
as “the opium of the people”) and Nietzsche (“God is dead”). But, according to
Morris, Darwin wins.
Darwin worries some Christians because they take him to be an obstacle to
believing in the literal truth of the Book of Genesis. But most scholars, even the
really devout, had given up on the literal truth of Genesis at least a quarter of a
century before Darwin published O. In the seventeenth century, there were
serious attempts to provide careful geological explanations of the phenomena
described in the Biblical narrative. The Reverend Thomas Burnet wrote The
Sacred Theory of the Earth to try to sort out the mechanics of the Noachian
deluge. During the eighteenth century, naturalists became convinced that fossils
were genuine remains of previous organisms, and, towards the end of the
century, the Scottish geologist, James Hutton, concluded from a careful
examination of geological strata that the earth must be significantly older than the
Biblical estimates – “We find no vestige of a beginning, no prospect of an end”.
In the early nineteenth century, Cuvier’s extraordinary reconstructions of extinct
organisms from fragmentary remains convinced his audiences that life on earth
had gone through a series of phases in which very different animals had lived; it
was possible to discuss these as “successive creations”, punctuated by
catastrophes in which one set of organisms disappeared. Further geological
excavations established a worldwide ordering of strata, from oldest (deepest) to
youngest (nearest to the surface), characterized by a common ordering of fossil
animals (and plants). The oldest strata contained nothing but marine
invertebrates; above them were strata containing fish; later, came amphibians
and reptiles; later still, birds and mammals; at the top, in the most superficial
layers, were the remains of human beings. In contradiction with Genesis,
naturalists more and more came to believe that not all the animals had been
created at once at the beginning. The history of earth had contained successive
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groups of animals, and the most familiar ones, including our own species, were
quite recent. When God created the first animals, Adam wasn’t there.
Of course, some people resisted, but the evidence mounted. In 1831, Sedgwick
(the Reverend Adam Sedgwick, who would excoriate the unfortunate Chambers
a little more than a decade later), gave his farewell address as President of the
Geological Society, and “read his recantation”. Sedgwick declared that devout
geologists couldn’t suppose that “our old superficial gravels” represent the work
of the Mosaic Flood, but that it must be admitted that human beings were simply
absent from the earliest stages of life on earth. After 1831, no serious British
naturalist, however devout, thought that Genesis could be literally correct.
So what exactly did Darwin add? He answered a question that prominent midcentury scholars thought undecidable: if there have been successive systems of
organisms in the history of life on our planet, they must either be connected with
one another (as descendants to ancestors) or the later ones must arise by a new
act of creation. These are the alternatives, but which is the right one? Lyell, the
great exponent of uniformitarian geology (the approach that tries to interpret past
geological processes in terms of the processes we can see occurring in the
contemporary world) thought we could never resolve the issue – it’s the “mystery
of mysteries”. In essence, Darwin contended that we could know which
alternative is correct (the ancestor-descendant one) and that we could identify
the main cause that has produced the changes in the types of organisms existing
at the different geological epochs.
Ironically, it was Darwin’s use of Lyell’s method to frame the observations he
made during the voyage of the Beagle that led him to the resolution. Darwin
took with him the first volume of Lyell’s Principles of Geology (a present from
Fitzroy), and he received the others in South America. They taught him to see
present phenomena in terms of known forces acting over very long periods of
time. Like Lyell, he looked first at geological phenomena; unlike Lyell, he applied
the same perspective to living things.
A Perspective on Darwin’s Theory
I think it’s useful to divide the theory of evolution by natural selection into two
main pieces – a claim about the connectedness of life, and a claim about the
causes of its historical modification. The first is often called “the fact of
evolution” and can be formulated as follows:
All the organisms that have ever lived on the earth are connected by a
historical process of descent with modification.
The second, often known as “the mechanism of evolution” is:
The chief cause of evolutionary change is the process of natural selection.
But what is most significant about Darwin’s analysis, what sets it apart from the
evolutionary speculations of earlier authors (including his own grandfather) is the
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fact that he uses these claims to explain various facts about the living world. I
suggest that we see Darwin as constructing a toolkit for answering particular
kinds of questions about life and its history.
I think this perspective is crucial both for understanding how Darwin’s “long
argument” in O works, and for recognizing how the enthusiastic extrapolations of
Darwinism to social and psychological issues err. Effectively, Darwin provides us
with a style of explanation that we can deploy to understand certain types of
questions. What sorts of questions? The kinds of issues that had puzzled him
from the voyage of the Beagle on concerned the distribution of present
organisms (questions of biogeography), the similarities and differences among
organisms (questions of comparative anatomy and physiology), the
characteristics of the fossil record (questions of paleontology), and the fit
(“apparent design”) between organisms and their environments (questions of
adaptation). These issues are systematically addressed in later chapters of O,
through the provision of striking illustrations. Darwin uses the idea of descent
with modification and the idea of natural selection to generate responses to
obvious puzzles.
Biogeography was evidently important to him, for he was happy when his brother
Erasmus found the chapters on distribution most convincing, and agreed that this
was the most powerful form of evidence – indeed, it’s surely biogeography that
prompted him to recognize the connectedness of living things. Why are there
organisms on the Galapagos, like the famous finches, that are similar to the
mainland organisms of South America and yet specifically different both from the
mainland organisms and from one another? Darwin answers this in terms of a
history of migration from the continent, with subsequent adaptation to the local
environment; small differences in morphology – like the form of a finch’s beak –
may enable an organism to do better in the particular circumstances of a
particular island than its conspecifics, and, if the characteristic is heritable, it will
be passed on to descendants.
Similarly with comparative anatomy. Why do we find similar arrangements of
bones in the forelimbs of mammals – in moles, bats, dogs, whales, and human
beings? The limbs are used in many different ways, so that, in consequence,
some bones are elongated or compressed. But, Darwin suggests, the common
structure is to be understood in terms of inheritance from a shared ancestor.
Once again, hypothesizing a process of descent with modification allows us to
understand the relationships we can observe among living organisms. (As your
students with interests in the life sciences will understand, Darwin’s own use of
descent with modification in this area operates to explain the relatively gross
features of organisms; with the refined biochemical knowledge of today, we can
use the same idea to understand the kinship of related organisms at a far deeper
level, recognizing why they share proteins with similar structures and why there
are common DNA sequences.)
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So I suggest we think of Darwin’s theory as a proposal: try to explain the features
of living things by constructing histories of descent with modification, where the
modifications are largely brought about by natural selection. If you conceive of
it in this way, you can make room for the obvious thought that some of these
constructed histories might be much better supported than others, and thus resist
the claim that there are alleged “Darwinian principles” that drive you all the way
to the excesses of human sociobiology and evolutionary psychology.
The Structure of O
I read Darwin’s “long argument” as divided into three main parts. The first four
chapters are devoted to identifying a possible mechanism for modification of
lineages of organisms – natural selection. The next four chapters elaborate the
possibility that the history of life shows a process of descent with modification,
largely, but not completely, driven by natural selection, discuss a few telling
illustrations, and respond to some perceived difficulties. The remaining chapters
develop the explanatory promise of the apparatus with respect to large classes of
questions (biogeography and paleontology in particular).
In the opening chapters, Darwin seems to enunciate some major principles:
Variation.
Within each species there is always variation.
Competition. For any species, at almost all times, more organisms are
born than can survive and reproduce to their full potential.
Variation with respect to fitness. For any species, some of the variation
is relevant to the ability to survive and reproduce.
Hereditary variation in fitness.
For any species, some of the variation
relevant to the ability to survive and reproduce is heritable.
From these, we can derive the
Principle of Natural Selection
Within any species, heritable variations that improve the ability to survive
and reproduce will become more prevalent in successive generations.
I think it’s crucial to appreciate the fact that all of these principles, including the
last, would have been accepted by Darwin’s biological contemporaries, even
those who were most skeptical about O. Nobody doubted, and nobody should
have doubted, that variation, competition, variation with respect to fitness,
heritable variation in fitness, and even natural selection, exist. The serious issue
is about what consequences these facts and processes bring. For conventional
naturalists, the mechanism of change Darwin proposes is relatively trivial, merely
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amounting to the adjustment of characteristics within the collection of fixed traits
definitive of (essential to) a species. Natural selection is a way of weeding out
those slightly deviant forms that are less well adapted than the superior (“proper”,
“ideal”) members of the species.
What’s revolutionary about Darwin’s proposal is the suggestion that this
mechanism can produce changes that breach the species barrier, so that
descendants of organisms belonging to one species can belong to another. I
think Darwin began as he did because he anticipated that a bare attempt to point
to the similarities among organisms (as in the structure of the mammalian
forelimb, for example) as evidence for descent with modification would prompt a
legitimate demand for explanation as to how the modifications might have been
built up. Without a possible mechanism for change over historical time, Darwin’s
proposals about descent, like those of his predecessors (e.g. the unfortunate
Chambers) would have been doomed. So Darwin gives the details about a
process that can be recognized, once it occurs, as something that every
naturalist will find familiar. The claim is that it has a much more crucial historical
role.
There are two important points to make about Darwin’s proposed mechanism of
evolutionary change and about the conception of the history of life embodied in
O’s sole diagram. First, Darwin isn’t a strict Darwinian (as we understand the
term). For contemporary Darwinians, the variations that arise are random (in the
sense that they aren’t caused by the organism’s needs) and there is no
inheritance of acquired characteristics. Darwin allows for favorable changes to
be induced by the environment, and he thinks that what happens during an
organism’s life, as the result of its interaction with the environment, can
sometimes be passed on to the organism’s descendants. In these respects,
Darwin shares views with Lamarck (one of his much-derided evolutionary
predecessors). Second, Darwin differs importantly from Lamarck in
emphasizing the kinship of living things. The diagram he gives his readers
presents a tree in which all contemporary organisms have histories that can be
traced to a common root (although the final sentence of O hedges his bets about
whether there was a single source for life – and adds a Pentateuchal allusion,
perhaps designed to mollify religious sensibilities). A Lamarckian diagram for
the history of life would show independent lines, advancing from worm to higher
animal to human being at different rates; the existing worms are organisms that
haven’t gone very far in an evolutionary process; current human beings are
descendants of worms in a lineage that has gone through the changes much
more quickly.
Natural selection is Darwin’s device for understanding the fit between organism
and environment, so that we can explain the appearance of design without
positing a designer. Yet a large part of his case for evolution depends on
emphasizing the respects in which organisms aren’t particularly well-suited to
their surroundings – the rudimentary hindlimbs of sea-dwelling mammals, for
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example. Darwin gives striking illustrations of this theme in discussing
woodpeckers “on the plains of La Plata, where not a tree grows” (210) and
upland geese with webbed feet. In a book on orchids, written shortly after O –
which Darwin characterized in a letter as “a flank movement on the enemy” – he
elaborated the theme in great detail, showing how the complex structures in
orchids are devices that have been modified from ancestral parts to cope with
problems of cross-fertilization. (A wonderful example, not Darwin’s, was
provided by Steve Gould: the giant panda has what looks, at first sight, to be an
opposable thumb, which it uses to grasp the bamboo on which it feeds; in fact
the paw has all five digits with no possibility of opposing a “thumb”, and the
grasping is done by using a protrusion from the wrist, an enlarged radial
sesamoid; an ancestral structure has been co-opted to a purpose quite different
from the one it used to serve; it’s quite clumsy – like the Rube Goldberg devices
of the orchids – but it gets the job done; for more detail, see the title essay of
Stephen Jay Gould The Panda’s Thumb).
Another important type of evidence is gathered by looking at cases in which
animals that live in very similar environments have very different forms. Darwin
uses the example of cave-dwelling animals, suggesting that, if we thought in
terms of separate creations by a creator with intentions to produce good design,
we’d expect to find great similarities among the cave-dwelling insects (say) on
different continents. In fact, we discover that the insects are quite similar to the
other species of insects in the immediate vicinity, and quite different from the
cave-dwellers on other continents, indicating that the forms have been generated
from a process of descent with modification (182-3). In this case, we might think
of natural selection as working by dedicating resources used in the ancestral
forms for developing eyes to structures that prove more useful in the dark.
But the principal purpose of the central chapters is to confront directly some of
the major objections to understanding a characteristic in terms of natural
selection. You may want to focus on two particular difficulties: the evolution of
complex organs and structures, and the evolution of non-reproductive castes
among some social insects. The first is important because Darwin’s conjecture
about what he took to be a classic case of the problem – the eye – has been
strikingly vindicated in a century plus of research; nevertheless, the revival of this
general type of problem is the main driving force behind contemporary creationist
claims on behalf of “intelligent design”. The second is interesting because
Darwin suggests that the non-reproductive castes – neuters – are maintained
because it is good for the hive. Some commentators have seen this as an
anticipation of some twentieth century theoretical achievements in understanding
“kin selection”, but a more common verdict is that it is a betrayal of Darwin’s own
commitment to natural selection at the level of the individual, one that inspired
sloppy talk about “selection for the group” or “selection for the species” among
animal behaviorists in the first part of the twentieth century.
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The trouble with complex organs is that it’s not obvious how they can be built up
in the gradual way Darwin recommends. As creationists love to put it, “What use
is half a wing or half an eye?” Darwin’s response is that any slight sensitivity to
light might turn out to be beneficial, and we can imagine that this was refined in
stages. The response has been vindicated by comparative study of the various
types of susceptibility to light, and the discovery of naturally-occurring forms in
which the kinds of transitions Darwin seems to have envisaged are instantiated.
The contemporary version of the creationist argument from design (essentially an
update of William Paley’s response to Hume, in a work that was required reading
for Cambridge undergraduates in Darwin’s day) looks at complex features at a
more microscopic scale. The idea is that cells contain plenty of interacting
components – little machines, as creationists think of them – that couldn’t have
been built up piecemeal. The basic challenge is the same: tell us how these little
machines were formed by natural selection. The right response, it seems to me,
is to say that we need to do the comparative work of looking at the genomes and
protein structures found in related organisms, so that we can make sensible
hypotheses about what kinds of intermediate forms might have occurred.
“Intelligent design” creationists make up an implausible story a priori and then
challenge Darwinians to defend it. Since molecular biology has recently
developed an arsenal of tools that could be used in serious investigation of these
structures, we should reject the a priori guesswork, and suggest that the question
will only become tractable once the work in comparative genomics has been
done. (The modern version of the objection is due to Michael Behe Darwin’s
Black Box; I work out the reply just given in “Born-Again Creationism”).
The problem with non-reproductive castes among the social insects results from
the fact that natural selection would seem to eliminate organisms that sacrifice
reproduction, and to tell against organisms with a tendency to produce nonreproductive offspring. This is a special case of the problem of altruism:
biological altruism occurs when one organism raises the reproductive success of
others at reproductive cost to itself. This seems impossible to sustain in the face
of natural selection. Developments in the past forty years have shown that this
isn’t so. The mathematical biologist, W.D. Hamilton, pointed out that the genetic
basis for an altruistic trait could be passed on if the trait disposed its bearers to
make a sufficiently large increase in the reproductive output of kin; this is
because relatives will have a chance (how large the chance is depends on how
closely they are related) of sharing the genetic basis. Special chromosomal
conditions among the social insects ensure that daughters share all the genes
passed on from their common father, and have a 50% chance of sharing the
genes passed on from their mother; Hamilton’s arithmetic then reveals that
workers do better to assist their fertile sister (the queen) and to rear her offspring.
(This is beautifully explained by Richard Dawkins in The Selfish Gene; that book
also contains a good account of how altruism between unrelated organisms can
be introduced and sustained.)
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The last part of O is Darwin’s systematic account of how the tools he has
developed can be put to work. I like to focus on the chapter on biogeography,
both because it was so central to Darwin’s own thinking, and because it reveals
the nuances of his argument. There are two very interesting problems that his
account has to solve: (1) How do organisms radiate from continents to relatively
distant islands? (2) How does the account explain discontinuous distributions of
organisms?
These might not seems like hard problems at first sight. For example, it doesn’t
initially appear puzzling that finches might fly to the Galapagos; (although, if you
take a good look at a finch and understand the prevailing winds, it’s a bit more
perplexing than it initially seems). But the really tough cases are plants. How do
yet get plant seeds across miles of ocean? Darwin responded to this by doing
experiments on the ability of seeds to germinate after spending long periods in
salt water, and by feeding birds fish into which seeds had been inserted, and
then testing whether the seeds found in the excrement would germinate (31720).
The second problem is illustrated by the case of Alpine plants, which are quite
widely distributed around the world on mountaintops, but are not found at lower
elevations. Darwin explains this by supposing that, as the earth’s climate grew
colder, the plants radiated widely, reaching zones containing mountains that they
had previously not occupied. As a warmer climate returned, the Alpine varieties
were out-competed by other plants in the valleys and on the lower slopes. But
the colder conditions higher up served as summits from which they couldn’t be
displaced (321-32). In dealing with these problems, Darwin reveals his care
and caution in developing and evaluating hypotheses about the history of life.
O concludes with a very important chapter in which Darwin summarizes his
argument, and also points forward to a large range of research projects. I see
him as trying to identify the ways in which his toolkit needs to be extended, and
as specifying the domain in which he plans to employ these tools.
Methodological Issues and the Reception of O
Many of the people who reviewed O (including Sedgwick) complained that
Darwin was playing fast and loose with the canons of good science. Herschel
famously described Darwin’s method as “the law of higgledy-piggledy”, and, in
general, he was seen as deserting the proper inductive method (brought to
perfection by the great Newton) in favor of the hypothesis-mongering that
Newton had condemned (“I feign no hypotheses”). But Darwin saw very clearly
that a lot of theoretical science (including, he believed, Maxwell’s electromagnetic
theory) proceeded by introducing hypotheses that explain, in a systematic way, a
hitherto diverse set of perplexing phenomena. The methodological strategy of O
is to show very clearly how, on the hypothesis of “independent creation”, all sorts
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of phenomena are extremely peculiar – animals have atavistic traits (195-9),
there are woodpeckers in places without trees, and so on. All of these can be
explained in a unified way by introducing Darwinian historical explanations,
based on the ideas of descent with modification and natural selection.
Effectively, Darwin was making explicit a strategy for justifying claims about
unobserved events – paradigmatically events in the past – by using clues found
in the present. He was correct in viewing himself as extending the method used
by Lyell in reconstructing the history of the geological features on the earth. You
might point out to your students that this method is continuous with the sorts of
things detectives do – and the sorts of things parents do, when they find the
cookie jar empty and a happy-looking toddler with a chocolate-smeared mouth.
Even quite early on, some of Darwin’s reviewers saw that the theory “must be
judged by the way it groups and explains phenomena”, and that, so assessed, O
shows the clear superiority of the hypothesis that living things are related by
descent with modification to the hypothesis that species have been separately
created. As this point became generally appreciated, Darwin and Huxley could
claim victory for “the fact of evolution”, and the focus of criticism shifted to worries
about the power of natural selection to effect evolutionary change. The general
form of the serious objections was that there are constraints that make
hypotheses about the operations of selection impossible.
One concern, voiced by a Scottish engineer, Fleeming Jenkin in a review of
1867, attacked the view that natural selection could ever transcend a species
boundary; Darwin lamented that “Fleeming Jenkin has given me much trouble”.
Jenkin’s critique assumed a theory of “blending inheritance”, to the effect that the
characters of the offspring would always be a compromise between the traits of
the parents. Hence, even if a favorable variation arose, its possessor would
have to breed with ordinary members of the species and the characteristic would
be constantly diluted. Jenkin illustrated the point with a racist (and imperialist)
example, to which nobody seems to have objected. He imagined a white
explorer conquering an island whose indigenous inhabitants were dark-skinned,
and suggested that, in being forced to mate with the native women, the white
newcomer would produce children with skin somewhat lighter than that normal in
the population – and that “the advantages of whiteness” would be diluted in the
generations; the island might be expected to have, for a while, a “more or less
yellow” chief, but there would be no enduring effect.
Darwin lacked any well-developed account of heredity, and was unable to do
more than point to cases in which inheritance didn’t seem to work as Jenkin
supposed. Mendel’s experimental work, published in a very obscure journal
(the Philosophical Transactions of Brünn) was unknown to him, and, even if he
had recognized Mendel’s achievement, it’s far from clear that it would have
helped, since, after the rediscovery of Mendel in 1900, it took well over a decade
to work out a synthesis between genetics and the account of natural selection.
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Another puzzle for Darwin was raised by Lord Kelvin who used estimates of the
energy received by the earth to put quite narrow limits on the time available for
the history of life. Knowing that some organisms hadn’t changed significantly in
a period of a few thousand years (mummified crocodiles from the Nile were
compared with living forms), Darwin was forced to admit an upper bound on the
speed with which natural selection works. Kelvin’s constraint suggested that
there wasn’t enough time for selection, operating at this, or a lower rate, to
produce gradual adaptations on the scale Darwin conceived of them. The
argument led to a number of hypotheses, eminently plausible in context: that a
trend, once started, had a momentum of its own; that relatively large variations
could sometimes occur; that environmental change can cause a large amount of
new variation. In the late decades of the nineteenth century and the first years
of the twentieth, the majority opinion among evolutionists was that Darwin’s
attempt to give priority to natural selection was a mistake, and that there were
other, more important, evolutionary forces. Kelvin’s puzzle was eventually
resolved when it was recognized that he had left out of account radioactivity as a
source of energy.
These kinds of criticisms are useful for illuminating how Darwin’s method is
properly held hostage to the information we think we have. In assessing the
possibilities of hypotheses of various sorts, we must honor anything that looks
like a well-grounded constraint. It seems to me that the career of Darwin’s claim
about the mechanism of evolution serves as a way of getting students to
appreciate the many assumptions taken for granted in our own view of nature.
There’s a further important point. Darwin showed, quite decisively, that some
hypothesis in terms of descent is superior to an alternative in terms of
independent creation, but that leaves open, in particular cases, the question
whether we can decide which form of evolutionary explanation to provide. This
point has occupied evolutionary theorists ever since Darwin, with some of them
happy to put forward plausible-sounding accounts and others insisting on a
rigorous screening-out of rival possibilities. The debate is fiercest when the
phenomenon to be explained concerns aspects of human behavior. Faced with
the claim that some type of asymmetry found between men and women
represents the action of past selection on the savannah (in the “environment of
evolutionary adaptedness”, or “Back in the EEA”, as the song goes), many
people, including me, want to insist that a quick story isn’t enough; you have to
show that alternative possibilities consistent with what we know about our own
evolution can be ruled out.
Darwin and Religion
In 1882, when Darwin died, the status of natural selection was sufficiently unclear
that people – like the Dean of St Paul’s – might assume that the Darwinian point
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was simply the fact of evolution, and that all that was required for Christianity to
accommodate it was to abandon the literal reading of Genesis. Many of
Darwin’s followers thought differently: George Romanes, for example, lamented
that “the universe for me has lost its soul of loveliness”. There are a number of
reasons for this attitude, some of which can be formulated without relying on
Darwin’s claim for natural selection, and others that become prominent if you
think natural selection has been the dominant cause of evolutionary change.
The first point is that Darwin vastly enlarges the scale on which the ancient
problem of evil plays out. As many of his readers recognized, the history of life
is one in which vast numbers of organisms, some of them sentient, have
perished – the amount of suffering is colossal, and sometimes extremely nasty.
Darwin himself refers to “ichneumonidae feeding within the live bodies of
caterpillars” (387); (ichneumonidae are parasitic wasps; the queen lays the eggs
within the body of a caterpillar, paralyzing the motor but not the sensory nerves,
and the embryos eat their way out). Moreover, most of it appears pointless.
Many of Darwin’s readers (and probably Darwin himself) have seen his account
of the history of life as non-progressive – to be sure, there are local adaptations
as a group of organisms, initially fitting imperfectly into a new or changed
environment, comes to modify the ancestral traits, but there’s no overall trend. In
the diagram O provides, we are simply one species among many, one twig on
the vast tree, and we shouldn’t think of the whole process as designed to
produce us.
Further, if you think of natural selection as generating adaptation, the traditional
argument from design collapses. The “wonderful contrivances” of organisms
turn out to be built up from chance variations that confer upon their bearers, in a
particular environment, a reproductive advantage. Moreover, Darwin instructs
us to look more closely, and to take note of the ways in which adaptations are
limited by the prior history. The designs are cobbled together out of bits and
pieces that happened to be available, and performance is limited in
consequence. No competent engineer would build the human knee or fill the
genomes of multicellular organisms with such a vast amount of repetitive and
currently useless DNA.
You can take the argument one step further. If there were a deity who designed
the history of life, and decreed that it be run by natural selection, then it would be
fair to bring a charge of sadism. For the suffering and death aren’t simply
unfortunately accidental to the large providential plan – they are built in.
Competitive struggle is the essence of the whole affair. If antelope acquire a
lucky variation, enabling them to outrun their predators, then cheetahs will starve;
if the cheetahs are the beneficiaries of mutational luck, then the antelope will be
eaten in greater quantities. The whole thing is an arms race. (Dawkins
develops this point very nicely in River out of Eden).
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So I think there are good reasons to think Darwin and providentialist religion don’t
mix well. Romanes’ sorrow was justified.
Darwin, Morality, and Society
In the wake of Darwin’s work, many people have wanted to connect evolution
under natural selection with our moral impulses and with the organization of
society. The initial impetus for this came not from Darwin himself, but from the
philosopher, Herbert Spencer, who, among other things, coined the slogan “the
survival of the fittest”; (this, by the way, isn’t a particularly good slogan, since
Darwin’s emphasis is on increased reproductive success, not on survival per se).
Spencer espoused a pan-evolutionism which he applied to ethical thought, and to
types of society. In various of his writings, he suggests that promoting a struggle
within society is a way of improving the society, and, not surprisingly, this idea
reinforced the proposals for social policy launched by successful capitalists.
Spencer was, for a significant time, even more of a star of the Victorian
intellectual scene than Mill (whose own political ideas were typically diametrically
opposed to Spencer’s), and he was amazingly popular in America. You can
find many public statements by John D. Rockefeller and Andrew Carnegie that
testify to Spencer’s influence. (You may want to talk about this with your
students; there are some selections in the Appleman reader, and Richard
Hofstadter’s classic Social Darwinism in American Thought contains some juicy
quotes.)
Darwin was much more cautious in drawing social implications, but, in D, he did
offer some speculations on human evolution, and he sets out the project of
understanding human psychology and morality in evolutionary terms. I
recommend using the selection from Chapter 5 of D (534-40; also 529-33, which
provide some useful preliminary material). This can lead into good discussion of
the relation of evolution to ethics, a much-debated topic in the past 150 years.
Darwin’s own thoughts are quite tentative, and concerned with the evolution of
moral capacities. In effect, he asks, “How did people become capable of
regulating their conduct?”, and the answer sketched (and it is a sketch) seems to
be that there were advantages to engaging in social activity, and a moral
sensibility was an enabling adaptation. Some people have read him as pointing
to a more ambitious program, one of giving an evolutionary explanation of
specific moral precepts. The idea would be that groups that adopted these
precepts gained an advantage in the “struggle for existence”, one that enabled
their members to out-reproduce the competition. A popular candidate for a
moral precept to be explained in evolutionary terms is the prohibition against
incest: the line is that accepting the rule “Don’t have sexual intercourse with
members of your immediate family!” is supposed to lead you to avoid bringing
into the world children with combinations of deleterious recessive mutations.
There are all sorts of reasons for worrying about whether this little just-so story
works.
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Darwin’s champion, T.H. Huxley, directly opposed the idea of an evolutionary
explanation of ethical principles. Huxley argued that ethics arises to check
tendencies that have evolved within our lineage. He offered the analogy of a
garden: the plants that grow naturally in a particular place may be quite various in
their abilities to compete with one another; the gardener makes decisions about
which ones to grow and which to weed out, and these often involve combating
the varieties that are most successful in reproducing themselves.
Many philosophers have been profoundly skeptical of any attempt to found ethics
on evolution. They have noted that all sorts of tendencies that might be
expected to enhance reproductive success (in particular contexts) are just the
sorts of things that our ethical precepts forbid – this was essentially Huxley’s
point. Further, they’ve suggested that any attempt to provide a naturalistic
account of good or bad, right or wrong, would invite the question: “Why should
my conduct accord with that standard?” (This is G.E. Moore’s famous “open
question”.)
In the last decades, however, a number of writers have tried to link evolution with
the sympathetic tradition in ethics, favored by Hume and Smith. The idea is that
human beings have evolved to be social animals, that central to this evolution
was an ability to respond to one another that gave rise to the “moral sentiments”,
and that we can understand those sentiments by placing them in their
evolutionary context. Although this may be along the right lines, it seems to me
to be much too crude as it stands. (My own view is that our evolution equipped
us with a disposition for limited sympathy that allowed a relatively primitive form
of sociality, that a decisive evolutionary step was the acquisition of a capacity for
governing our behavior by norms, and that, once we were able to express these
norms, there began a process of cultural evolution that has some affinities with,
but is by no means identical to, Darwinian evolution.)
Human Sociobiology and Evolutionary Psychology
Since the New York Times so frequently gives prominence in its science section
to provocative claims about the evolutionary shaping of human behavior, many of
your students are likely to think that people now know a lot about this area. We
don’t, and it’s worth discussing that with them.
In the 1970s, a group of evolutionary biologists, of whom E.O. Wilson was the
most prominent, suggested that the grand questions about human nature could
be answered by biology, and, to some extent, by evolutionary biology. Wilson
claimed that women are, by nature, cautious and coy, while men are hasty,
aggressive, and promiscuous. Hierarchical divisions are built into human
societies. Xenophobia is part of our makeup. We are “absurdly easy to
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indoctrinate”. Others proposed that men have a genetically based tendency to
rape.
These conclusions – advanced by Wilson in a relatively gentle and regretful
spirit, by others in a more in-your-face fashion – were based on the following
chain of ideas. First, it’s alleged that a certain form of human behavior (sexual
division of labor, say) is universal, found in all (well, a wide range – well, some
that we happen to have read about) societies. Next, it’s claimed that there
would be an evolutionary advantage to the behavior. Then it’s supposed that
the behavior must have evolved under natural selection. But natural selection
can only operate where there’s a heritable trait. Hence there must be a genetic
basis for the behavior. So this means that the behavior will be fixed by our
biology – or, at least, relatively hard to change.
This line of reasoning (?) is flawed at almost every step. First, the claims about
universality are often subject to challenge. Second, the ideas about evolutionary
advantage are rarely articulated by doing what serious evolutionary theorists do
all the time, namely working out the details of how the reproductive advantages
are gained, and eliminating rival hypotheses. Finally, the fact that selection can
only work where there are genes to select means that in the environments under
which evolution occurred, certain genes give rise to the trait in question; that
doesn’t imply anything about different environments that social engineers might
try to construct.
Here’s a concrete example to illustrate the second and third problems. Consider
the claim that men can be expected to desert the mothers of their children and go
off to procreate elsewhere. The basic idea is simple: once a child is born, the
mother is stuck and the father can increase his reproductive success by finding a
new mate. Too simple. Effectively, fathers and mothers are engaged in a
game with two strategies for each – Desert or Stay. Whether paternal desertion
is better than paternal staying depends on all sorts of things: the chances of kids’
surviving if brought up by two parents, or one, or by zero; the chances of finding
a new female to mate with if the father deserts; the competition for mating with
such “unattached” females. Given plausible assumptions, you might even think
that the best strategy might depend on what others are doing. If all the other
men are chasing around looking for new opportunities, a particular male might do
much better by staying home and helping raise the existing child. Of course,
nobody knows what the relevant parameters were on the savannah (back in the
EEA), so you can make things up to suit your tastes. But even if male desertion
were a preferred strategy on the savannah, and there were genes that, in the
savannah environment, caused males to have a tendency to desert, and even if
those genes are now found in contemporary men, that doesn’t mean that in the
radically different context of current society those genes cause the same
behavior. They may lead us in different psychological directions, and the male
promiscuity on which the sociobiologists loved to remark may reflect cultural
causes.
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Human sociobiology was criticized during the 1980s, and there was a fair bit of
public distancing from the excesses: people who now called themselves
“Darwinian anthropologists” or, later, evolutionary psychologists, complained that
critics didn’t really appreciate the extent to which the movement was policing
itself. A common response was to say that the critics were making just the
points that the more thoughtful scholars in the evolution of human behavior had
independently arrived at. That lasted until 1990, when the old stories came
lurching back. They’re now with us in full force, in David Buss’ work on the
evolution of sexual desire and jealousy, in Randy Thornhill’s study of the
evolution of tendencies to rape, in Leda Cosmides and John Tooby’s claims
about the evolution of psychological modules for detecting social cheating, and in
the diatribes issued by Steven Pinker about “How the Mind Works” and against
“The Blank Slate”.
Some of this (e.g. the work of Cosmides and Tooby) is a bit better than some of
the excessive stuff in human sociobiology; and sometimes (as with Buss) there’s
a serious attempt to do some sort of cross-cultural study. But the movement is
plagued by the same old problems: most importantly, the movers make up
evolutionary stories without considering the details or the merits of alternative
explanations. (I’ve elaborated this point relatively briefly in my contribution to
The Cambridge Companion to Darwin, and, at greater length, in “Pop
Sociobiology Reborn”.)
Concluding suggestions
I hope these notes will give you a start on some of the issues you might treat in a
session (or two) on Darwin. Specifically, you might want to discuss:
What was the background to O?
What was novel in it?
What exactly is the theory of evolution under natural selection?
How did Darwin defend the theory?
Was his defense compelling?
Did Darwin introduce a new conception of method in the sciences?
Have all the problems in Darwin’s initial theory been resolved?
What are the implications of Darwin’s views for religious belief?
Can Darwinism be applied to societies and social institutions?
Can evolution explain anything about ethics?
What, if anything, can evolutionary theory explain about human
psychology and human behavior?
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Sources
Historical Studies. There are several excellent biographies of Darwin, of which I
particularly recommend Janet Browne’s two-volume study. Darwin’s
Autobiography is also well worth reading. For background in nineteenth century
science, and the relations of Darwin’s views to those of his predecessors, you
might consult C.C. Gillespie Genesis and Geology, and Michael Ruse The
Darwinian Revolution. Adrian Desmond has a terrific biography of Huxley.
Phillip Sloan’s essay in the Cambridge Companion is a good concise source.
Analyses of O. Quite accessible is Ernst Mayr One Long Argument, although it
is philosophically crude in places. I think the best treatment is that of Jonathan
Hodge “The Structure and Strategy of Darwin’s ‘Long Argument’” (Brit. J. Hist.
Sci. 10, 1977, 237-46). I offer a similar view in “Darwin’s Achievement”
(reprinted in In Mendel’s Mirror [IMM]).
Reactions to O. David Hull Darwin and his Critics is a superb anthology. It
contains selections from many important reviews, including that of Fleeming
Jenkin.
Creationism and Responses to it. Reading Creationists isn’t good for the
neurons. You can get some quotes in my book Abusing Science, or in Douglas
Futuyma’s Science on Trial. Probably the best statement of modern (“Intelligent
Design”) Creationism is that given by Michael Behe in Darwin’s Black Box. For
treatments of IDC, you can read Robert Pennock Tower of Babel, and Pennock
(ed) Intelligent Design Creationism and its Critics; this collection contains my
essay “Born Again Creationism”, which is also in IMM.
Evolution since Darwin. Richard Dawkins is a good source for lots of things. I
recommend looking at The Selfish Gene and The Blind Watchmaker. You can
balance this with Stephen Jay Gould’s collections, especially the first two: Ever
Since Darwin and The Panda’s Thumb. You may also enjoy Dan Dennett
Darwin’s Dangerous Idea.
Implications for Religion. Dawkins’ River out of Eden is quite useful here.
Social Darwinism. The Appleman anthology has some useful passages from
Carnegie. Richard Hofstadter’s Social Darwinism in American Thought is a
classic.
Evolution and Ethics. Huxley’s lecture with this title (excerpted in Appleman) is
another classic. A very crude version of evolutionary ethics appears in E.O.
Wilson On Human Nature. I respond to this in “Four Ways of ‘Biologicizing’
Ethics” in IMM. For a more sophisticated evolutionary approach, see Simon
Blackburn Ruling Passions. My own version is given in “Biology and Ethics”,
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forthcoming in the Oxford Handbook on Ethics (if you want a copy just let me
know).
Human Sociobiology and Evolutionary Psychology. Wilson On Human Nature
is a good source for human sociobiology. Reactions include a fine chapter of
Richard Lewontin et. al. Not in our Genes and my book Vaulting Ambition:
Sociobiology and the Quest for Human Nature (more about what’s wrong with
sociobiology than you need, or want, to know). For evolutionary psychology,
you can consult the relatively serious collection J. Barkow et.al. (eds) The
Adapted Mind, especially the articles by Leda Cosmides and John Tooby. David
Buss The Evolution of Desire, and Steven Pinker The Blank Slate are
considerably worse. The real nadir comes with Buss Jealousy and Randy
Thornhill and Craig Palmer The Natural History of Rape. My criticisms are
presented briefly in “Giving Darwin His Due” (Cambridge Companion to Darwin)
and, with respect to Buss, Thornhill and Palmer, in “Pop Sociobiology Reborn”
(co-authored with Leah Vickers, who, as a Columbia senior, became critically
inspired by evo psycho) in IMM.
Jonathan Hodge and Gregory Radick The Cambridge Companion to Darwin
includes lots of different perspectives on different parts of Darwin’s work and
influence. It’s worth reading.
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