The Legacy of Charles Darwin
David A. Stelzig
"…it would seem to require a greater infinity of power
to cause the causes of effects, than to cause the effects themselves"
Erasmus Darwin, 1794
Rain, gentle but steady,
chilled the air and decreased visibility early in the evening of October
2, 1836, but lights of Falmouth finally twinkled on the horizon and
quickly brightened as His Majesty's Ship Beagle soundlessly approached,
then dropped anchor in the safe waters of the harbor. Only then did
huzzahs and laughter roll from the deck of this tiny ninety-foot sailing
Charles Darwin was about to set foot on
soil of his native England for the first time in half a decade. He had
spent five years observing, chronicling, and sampling the geology and
biology of lands in the southern hemisphere, including the Galapagos.
Darwin's specimens, along with written
and oral discussions of his findings, would bring him fame. He would
be praised both in person and print. He would be voted a member of The
But Darwin was not well. Indeed, for the
rest of his life, he endured chronic depression, indigestion, and headaches
so severe that he was confined to bed for months at a time. The cause
of Darwin's illness? No one is certain. Lactose intolerance has been
suggested. So has some rare tropical disease. However, most scholars
think the explanation is at least partially psychosomatic.
Simply stated, Darwin was racked with
guilt because he was burdened with a frightening secret. Darwin knew--he
was absolutely sure that he knew--species in existence today were not
created by God.
It was not only that Darwin saw changes
in species, or even the appearance of new ones. Other free-thinking
scientists and philosophers--including Darwin's grandfather, Erasmus--had
already suggested that species were mutable. But this was just taken
as evidence of God's direct hand in the continuing process of creation.
The Garden of Eden remained Gospel. Man was still the only animal infused
with an everlasting soul.
Darwin's sin was that he concluded these
changes occurred by a process that precluded the direct involvement
of God. They had come about by natural selection: random changes in
earlier species had made the organisms more fit to survive and so these
changes were passed on. Eventually, an accumulation of such changes
made the subsequent progeny so different that they were, in fact, new
And not just some species. All species.
If this mechanism worked for the finches and tortoises of the Galapagos,
it also worked for man.
Darwin's theory of natural selection didn't
come as an intuitive flash on the Galapagos. He returned to England,
awed by the diversity of organisms he'd seen, but believing an all-powerful
God had created them to perfectly fit their unique environments. Then,
five months after Darwin's return, ornithologist John Gould informed
him that his collection of Galapagos songbirds included as many as twelve
varieties of ground finch, all slightly different from the finches of
South America. Darwin had been careless in tagging his own specimens,
but with the aid of more carefully labeled collections from Captain
FitzRoy and crew members of the Beagle, he was able to determine that
his finches were segregated by type on the individual islands of the
Galapagos. He started to think he was on to something truly new.
Darwin theorized that continental finches
somehow became isolated on the Galapagos and were thus subjected to
the harsh conditions of these islands. Many were unable to survive.
A few, however, transmuted into more fit species and therefore became
the dominant populations.
Darwin soon became convinced of the validity
of natural selection, but was not yet willing to publish. Some have
suggested this reluctance was partially due to the widespread condemnation
of Robert Chambers' 1844 anonymous essay, "Vestiges of the Natural History
of Creation." More likely, if this primitive argument for evolution
had any effect on Darwin, its absence of scientific support merely galvanized
his natural tendency toward meticulous documentation.
Whatever the reason, Darwin discussed
his theory with friends, but didn't publish. Not yet. He had planned
to polish the writings about his terrible knowledge for another two
years, but then, in 1858, he received a manuscript in which Alfred Wallace
outlined a mechanism for the appearance of new species nearly identical
to his own theory of natural selection. At the time, Darwin was despondent
about his eighteen-month-old son, Charles Waring Darwin, who succumbed
to scarlet fever on June 28, and so he asked his friends, Charles Lyell
and Joseph Hooker, to decide how to handle the matter. They quickly
agreed on simultaneous publication. On July 1, 1858, the theories of
Darwin and Wallace were presented in a single reading to the Linnean
Society of London.
A little over a year later, in November
1859, Darwin published "On the Origin of Species by Means of Natural
Section, or the Preservation of Favoured Races in the Struggle for Life,"
a more complete discussion of his theory and arguably the most important
biology book ever written. Largely because of this wildly popular text--the
entire printing sold to wholesalers in a single day--evolution soon
became mainstream science.
Other mechanisms have been
proposed to help explain evolution, but natural selection is still considered
a mainstay of the process. Indeed, creationists frequently argue interchangeably
against evolution and natural selection, believing, with some justification,
disproving either will disprove both.
That was an easier task for Darwin's
contemporaries because the laws of heredity were not understood. The
concept of molecular biology could not even be imagined. Since Darwin,
however, considerable scientific data have accumulated that support
the theory of natural selection. Gregor Mendel, for example, in his
landmark studies of the garden pea, demonstrated that discrete units
of genetic information are passed with mathematical precision from parent
to offspring. These units of information, now known as genes, were shown
to be DNA. And, in 1953, in a laboratory at the University of Cambridge,
a scant seventy-five miles north of the ancestral home in which Darwin
wrote "Origin," physicist Francis Crick and his graduate student James
Watson determined the three-dimensional structure of DNA.
To most biologists, the Watson-Crick model
made it intuitively obvious that genetic information in the long DNA
polymer is due to the sequential order of the subunits. It is as if
DNA is a long chain made up of links of four different shapes.
Building on this metaphor, replacing a
square link for one that's round in the DNA chain responsible for flower
color might be enough to change the bouquet from pink to white. Likewise,
substituting a couple triangular links for square in one year, a round
link for oval many years later, and a few oval links for triangles,
after another million years or so, could cause an organism to become
an entirely new species.
This metaphor is a simplistic illustration
of point mutations, one mechanism used in natural selection. An example
is sickle cell anemia, a genetic disease that's a blessing in disguise:
people who inherit this disease have a significant resistance to malaria,
a more deadly disease. Not coincidentally, sickle cell anemia only occurs
in people who live--or whose ancestors lived--in areas where malaria
Sickle cell anemia is caused by a point
mutation in a recessive gene containing the DNA with the blueprint for
the synthesis of hemoglobin, the red blood cell protein that carries
carbon dioxide and oxygen to and from the lungs. One subunit of that
DNA has a shape (adenine) substituted by another (thymine). Hemoglobin
synthesized from this faulty blueprint has the hydrophobic amino acid
valine on the surface of the protein rather than the water soluble glutamic
acid, and these abnormal hemoglobin molecules tend to clump together
in an effort to get the valine out of contact with the aqueous environment
of the cell. If a child receives the sickle cell gene from both parents,
this clumping is so severe that the hemoglobin forms long chains that
push the red blood cell into a sickle shape, resulting in early destruction
of the cell and, often, death of the individual. However, it is much
more likely for a child to receive the sickle cell gene from just one
parent, in which case there are essentially no symptoms of anemia. More
to the point, if an infected mosquito injects that child with the malarial
parasite, he may become sick but will almost certainly survive. In contrast,
without the sickle cell mutation, death would have been highly likely.
Point mutations are not
the only genetic changes involved in natural selection. Another is jumping
genes (transposons), the discovery of which earned Barbara McClintock
the Nobel prize in 1983. If point mutations are considered one-letter
changes in the genetic code, jumping genes are whole words, sentences,
or paragraphs that have moved from one location in a chromosome to another.
This can be within a single chromosome, from one chromosome to another,
and even between species, for example from an invading virus to the
genes of its host. A measure of the significance of this process in
evolution is the estimate that as much as 45% of the human genome originated
as jumping genes.
Natural selection is an
essential piece of the evolution puzzle, but not the only one. Another,
genetic drift, is considered by many scientists to be at least as important.
Natural selection explains nonrandom shifts
in a population due to point mutations and other gene modifications.
It is survival of the fittest. In contrast, genetic drift is survival
of the luckiest. It is caused by a random event in a population which
results in a change in the gene pool of that population. Consider, for
example, an isolated group of people in which only one couple has the
genetic ability to give birth to a blue-eyed baby. If they never have
children, or if all their offspring die without giving birth, the genetic
blueprint for blue eyes will immediately disappear from that population.
Real life is more complex of course and it takes numerous generations
for a genetic trait to drift out of--or to become established in--the
total gene pool.
Genetic drift doesn't usually have much
effect in a large population because random changes, like the relative
number of brown- and blue-eyed babies, tend to average out. But in small
populations the effect can be profound.
Small populations can arise in many ways.
A typhoon can blow songbirds to distant islands. Religious people, such
as the Amish, can segregate themselves from society. Advancing glaciers
of an ice age can divide a population into two or more small groups.
Whatever the cause, radically decreasing the population size significantly
increases the importance of genetic drift.
Creationists don't usually pay attention
to the concept of genetic drift. This is at least interesting, considering
that many of them believe the story of Noah and his ark, which, if true,
would be the granddaddy of all population decreases.
It has been one-hundred-fifty
years since Darwin published the first edition of "Origin." During this
time, an overwhelming body of evidence has accumulated in support of
the theory of evolution. In contrast, experimental evidence of creationism
has been zero. Because of this, the percentage of credible scientists
arguing against evolution has become vanishingly small.
And yet, that number is not zero.
One of the more common claims of creationists
is that anything exceedingly complex presupposes the existence of a
creator. Theologian William Paley first made this argument in 1802 by
stating the existence of a pocket watch proves there is a watchmaker
because the individual components could not have come together accidentally.
A recent biological example of this argument of "irreducible complexity"
is the flagellum, a whiplike appendage used for locomotion by some bacteria.
The flagellum is composed of as many as thirty distinctly different
proteins. Creationists have argued that since none of these proteins
have any other function, they must have been created as a working flagellum.
Like the pocket watch, the flagellum could not have happened accidentally.
But some organisms have functioning flagella
that are relatively simple. It is now also known that some pathogenic
bacteria have a handful of proteins nearly identical to those of complex
flagella that function not in motility, but rather in the injection
of toxins into the cytoplasm of their hosts. It is conceivable that
these "membrane transport machines" served as evolutionary precursors
to the more complex flagella.
Creationists try to debunk evolution by
stating that it can't explain the origin of life. Some laboratory experiments
have shed light on how components of DNA and proteins, and even membrane-bound
organelles, might have originated on a prebiotic earth, but it's true
that the origin of life is still a mystery. It can even be argued that
the existence of life on earth supports a belief in a creator--or an
ancient visit by aliens. But it isn't evidence. Furthermore, it has
nothing to do with the multigenerational evolution of a biological organism
into a new form.
The second law of thermodynamics states
that in a closed system there cannot be a decrease in randomness (entropy).
Creationists sometimes say that thermodynamics proves man could not
have evolved from more random organisms. But suggesting this while ignoring
energy sources that fuel evolution--such as food digestion and, ultimately,
nuclear fusion of the sun--is no more logical than ignoring human muscle
and man-made machines and deciding that a pocket watch is much too complex
Some creationists think it mathematically
impossible that complex molecules, let alone organisms, came about by
chance. They sometimes use Shakespeare's, "To be or not to be," as an
illustration. Randomly selecting one letter every second, it would take
longer than our earth has existed to come up with the correct spelling
of this thirteen-letter phrase. But of course that's not how evolution
works. Existing molecules--and, yes, organisms--evolve by chance additions
or changes, but they don't throw out the past until something better
happens along. In the Shakespeare example, if incorrect letters are
discarded and correct ones kept, "tobeornottobe" could be written in
less than six minutes.
Creationists have other
ostensibly scientific arguments in their arsenal, but they are no more
threatening to the theory of evolution than the ones discussed here.
So what argument does that leave? Religion. Christianity, Islam, and
Judaism all teach that man was created by a God and that playing by
the rules will earn man the right to live with that God for all eternity.
We are simply too egotistical to believe that a loving God would be
so insulting that He would create us in His image by letting us evolve
from some stupid and soulless animal.
Evolution doesn't preclude
the existence of God. Or even the infusion of an eternal soul at a key
point in the development of some prehistoric primate. And the evidence
supporting evolution is vast. Nonetheless, creationism is still widely
believed by many people. This is especially true in the United States,
and that fact may hold some explanation to this enigma.
According to a recent survey, only approximately
40% of Americans believe in evolution. In Europe, the number is closer
to 80%. To a large extent, this correlates with the presence of fundamental
Christians in the United States who view the Bible as the literal word
of God. In contrast, European Protestants and mainstream American Protestants
consider Genesis to be metaphorical.
The conservative wing of the Republican
Party, especially in recent years, has contributed to the problem by
making opposition to evolution a prominent part of their campaigns.
Finally, many in the United States have
a poor understanding of modern genetics. For example, in one survey,
fewer than half of American adults were able to provide even a minimal
definition of DNA.
In Darwin's age, individuals
who didn't believe in evolution called themselves "creationists." That's
an honest title and they were honorable men. They made their arguments
using accepted science of the day and they did this in scientific publications
and at meetings of fellow scientists.
In the United States, twentieth century
creationists focused their fights against evolution in the courtroom.
In one notorious example, John Scopes was found guilty, in 1925, of
teaching evolution to his high school students. The Tennessee law he
violated was declared unconstitutional, but not until the 1960's.
Also in the 1960's, the term, "creationism,"
morphed into "scientific creationism" and a few school boards required
this belief to be taught along with the teaching of evolution. When
tested, these laws were found to be religious and thus have been declared
Most recently, creationism has been called
"intelligent design'" as in the phrase, "the science of intelligent
design." And again, because of the constitutional requirement for the
separation of church and state, laws requiring the teaching of intelligent
design have been declared unconstitutional.
The creation/evolution debate
will certainly continue. That's all right. Creationists could even be
correct. But if so, creation must be by some mechanism that includes
evolution because this science is testable and has been tested. It is
still considered a theory only because exact details haven't been worked
out, but the overall concept of evolution is a proven scientific fact.
David A. Stelzig is a retired professor and Chairman
of Agricultural Biochemistry at West Virginia University. Stelzig has
numerous research publications in refereed journals, including Science,
Plant Physiology, and Phytochemistry. He also has short fiction published
in Boston Literary Magazine and DiddleDog, and stories
accepted in Midnight Showcase and an anthology of MD authors,
but “Legacy” is his first piece of creative nonfiction.