Prof. Bleen (6_bleen_7) wrote,
Prof. Bleen

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Dance Dance Evolution! (Part One)

(Title borrowed from Cruel Site of the Day)

The people at Gallup conducted a poll, late last year, that illustrates what I consider to be the greatest danger facing America today. I've been stewing about it ever since, and I'd like to offer you a huge, steaming bowl of stew.

The poll concerned Americans' viewpoint on the theory of evolution. Only 35%—about one in three—Americans surveyed believed evolution to be "well supported by the evidence." That is simply frightening.

I strongly suspect that the one-third of American who believe evolution to be well-supported by the evidence are precisely the one-third who understand, at least at a basic level, what the evidence actually is. And there lies the problem: the crisis of science education in the US. I don't believe that science teachers are to blame, although if teachers were adequately paid—and had more opportunity to actually teach, as opposed to baby-sitting—we would undoubtedly see a sharp upswing in the quality of teaching in the sciences. No, the root of this crisis appears to be a general hostility to science and science education held by the American people. People who have grown accustomed to being told how to think by their preacher, or their TV set.

I don't intend to present a detailed scientific argument in favor of evolution—many have already done so much more eloquently than I could (see the essays of Stephen Jay Gould, for example)—but rather to disparage the sheer folly of the denial of evolution, in the context of history, modern society and the Bible itself. None of these ideas is beyond the average American...if they would just think.

This rant got so long that I had to split it in two. The historical section grew out of control, once I came to realize that it was a good opportunity to write about how scientific thought displaces popular misconception, using our good friend Galileo as the centerpiece. In consequence, I'll speak of astronomy as much as biology.

In this first section, let's look at what history has taught us so far:

For most of human existence, the vast majority of people believed the world was flat. And they were wrong. Every one of them. So much for going by the vote! Let's make that Major Lesson One: Natural law does not obey the will of the majority.

A famous scientist stated Major Lesson One in a slightly different context:

When it was first said that the sun stood still and the Earth turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as every philosopher knows, cannot be trusted in science.

(To find out who wrote this wonderful sentence, and in what context, read on.)

This is not to say that people were stupid—until quite recently—for thinking the Earth was flat. How could you convince a Native American living in Kansas a few thousand years ago that the Earth was round? All the available evidence then and there pointed to a flat Earth. Rather subtle observation is actually required to conclude that the Earth is (essentially) a sphere, and not a disc. Still, the ancient Greeks, and others, made those observations well over two millennia past; and one Greek mathematician, Eratosthenes (ca. 276-196 B.C.E.), accurately calculated the Earth's circumference (about 25,000 miles) around 240 B.C.E.

(Another Greek, Poseidonius (ca. 135-50 B.C.E.), used a different method and obtained a figure of only 18,000 miles. This latter estimate seemed more reasonable to the Greeks, who felt uncomfortable with an Earth's surface much larger than their known world, so it became the accepted figure. As a result, Christopher Columbus expected the distance west from Spain to the Indies to be about 7,000 miles less than it really was—which is why he initially thought he'd reached the Indies when he stumbled upon the Americas.)

After the ancient Greeks, no educated, thinking person doubted the world was spherical—but precious few people were educated in those days, or indeed at any time until the last 100 years or so. Nowadays, of course, it is sheer folly for anyone from an industrialized nation to believe the world to be flat, in the face of incontrovertible evidence to the contrary. Think of how much we depend on our communications and weather satellites! If the GPS network went down, for example, American commercial aviation would grind to a halt. I hardly need to tell you, the educated reader, that until we conquer gravity, we can't have satellites and a flat Earth. (I'm talking about an infinitely extended flat surface, here. One could, of course, orbit satellites around a disc-shaped Earth, but the concept of an orbit would not likely occur to the people living on such an Earth.)

The motion of the planets relative to the Sun presented a thornier problem. Until the last 500 years, even educated people had no convincing reason to think that the Earth and the (other) planets revolved around the Sun. It seemed obvious, to early astronomers, that the stars and all the planets (including the Sun and Moon) revolved around the Earth, even though the paths of the planets, except the Sun and Moon, were considerably more complex over time than those of the stars, which traced simple circular paths through the sky and moved at a constant rate.

Again, at least one ancient Greek philosopher, Aristarchus (ca. 320-250 B.C.E.), believed the Sun to be the center of the solar system, but that was largely because he estimated the Sun to be considerably larger than the Earth. He used a trigonometric method, like that of Eratosthenes, to calculate the distance between Sun and Earth; and he estimated that the Sun's diameter was about seven times that of the Earth. (Aristarchus' figure underestimated the true distance by more than tenfold. The Sun is actually much larger than even he realized.) To appear as large in the sky as it does from a distance of 8,000,000 miles, the Sun must outsize the Earth by severalfold; and if the Sun is that much larger than the Earth, then it seemed reasonable to assume that the Sun is that much more massive; and it also seemed reasonable to supposed that the smaller body revolves around the larger body, just as the Moon revolves around the Earth. To his credit, Aristarchus also pointed out that the motions of the planets relative to the stars could be explained more easily if it were assumed that the Earth and planets revolved around the Sun—a "heliocentric" model of the Solar System.

Later, Hipparchus (ca. 190-120 B.C.E.) carefully worked out a mathematical model for the motion of the heavenly bodies, using a system of overlapping circles to describe the orbit of each body around the Earth. This "geocentric" model, although wickedly complicated, was more useful in predicting the motion of the heavenly bodies than the heliocentric model (which was not worked out in as much detail), and of course agreed much better with people's expectations. It was all very good to claim that the Earth revolved around the Sun, but without convincing evidence in favor of such a notion, nobody could reasonably be expected to embrace it in the face of common sense. Thus, the geocentric model, as described and systematized by Claudius Ptolemaeus (a.k.a. Ptolemy, ca. 75 C.E.-?), was accepted without question all through the Middle Ages.

The heliocentric theory was not given serious thought again for 18 centuries after Aristarchus, when the Polish astronomer Nicholas Copernicus (1473-1543) began to derive a mathematically rigorous system of planetary motions with the Sun at the center. Copernicus' model explained some basic facts with elegant simplicity, especially regarding the orbits of Mercury and Venus, which planets never stray very far from the Sun in the sky. It also gave a straightforward reason for the occasional "retrograde" movement of the planets Mars, Jupiter and Saturn. Once a year, these planets appear to reverse their path across the stars, as the Earth overtakes them in its faster orbit around the Sun.

Although conceptually pleasing, the Copernican model did not greatly reduce the complexity of the geocentric model. Copernicus assumed, as Hipparchus had done, that the planets orbited in combinations of perfect circles, and thus was required to add small circles to the main ones in order to approximate the true planetary motions (see below). Still, the Copernican system explained enough about the solar system that it began to gain adherents within the scientific community.

Fearing reprisal from the Church, Copernicus hesitated to publish his entire theory. The book was not released until just after Copernicus' death. His publisher, also worried about trouble with religious authorities (intriguingly, because Martin Luther, rather than the Pope, had denounced the heliocentric theory), hastily added a preface that stated, in so many words, "We don't mean to suggest that the theory explained here reflects reality, but merely a convenient mathematical system to predict planetary motions." The Catholic Church eventually placed the book on the Index (i.e., the list of banned works), but the theory quickly became popular among astronomers.

One of these Copernican converts was the young Johann Kepler (1571-1630), who dealt the geocentric theory a fatal blow by using the excellent planetary observations of Tycho Brahe (1546-1601) to develop an improved version of the heliocentric model in which the Earth and planets moved in ellipses rather than circles. This new model explained the motions of the heavenly bodies to near perfection using only a single ellipse for each orbit! Any open-minded scientist, comparing the two models, would have to conclude that Kepler's was far more satisfactory than the geocentric model.

It was left to Galileo Galilei (1564-1642) to administer the coup de grace to the geocentric model still endorsed by the Church. Gazing through his new telescope (the first one ever used to observe the heavens), he discovered four small bodies orbiting the planet Jupiter. The existence of these Galilean satellites (later named Io, Europa, Ganymede and Callisto) was utterly incompatible with the ancient Greek theory of the Solar System—yet anyone who cared to look through the telescope could see them. (Amazingly, a few individuals refused to look, saying that if the satellites did not appear in the works of the Greek philosopher Aristotle (384-322 B.C.E.), they couldn't possibly exist.) Furthermore, Galileo turned his telescope toward Venus and found that as it orbits the Sun it goes through a complete set of phases, just like the Moon. Under the geocentric model, Venus must always remain closer to the Earth than the Sun is; therefore, Venus will always show a crescent. Observation of a gibbous or nearly-full Venus (Venus at full would be directly behind the Sun and not visible) indicates that Venus must swing around behind the Sun, leading inescapably to the conclusion that Venus orbits the Sun and not the Earth. After these discoveries were made public, no educated, thinking person would doubt the heliocentric model of the Solar System.

Both brilliant and somewhat of an asshole, Galileo made many enemies. His revolutionary views and discoveries were not taken well in Rome, and as a result Pope Pius V in 1616 declared the Copernican model heretical. Nevertheless, a few years later, Galileo published a book on the geocentric and heliocentric theories that Pope Urban VIII construed as an attack on his holy person. The book was placed on the Index, and Galileo, by then an old man, was hauled up in front of the Inquisition. In 1633, under threat of torture, he officially recanted his heretical views.

Why were Copernicus' and Galileo's theories construed as heresy? Because—say it with me now—they contradicted the Bible. The Old Testament contains several passages that clearly indicate the Earth as the immovable center of the Solar System. Most famous, perhaps, is Joshua's commanding the Sun to stop in its path around the Earth, during the battle of Jericho (Joshua 10:12-14). The 93rd and 104th Psalms indicate that the earth is immovable. In fact, John Calvin cites the 93rd Psalm in his denunciation of the heliocentric theory, in which he asked, "Who will venture to place the authority of Copernicus over that of the Holy Spirit?" If you need any more convincing, take a look at this passage from the decree of the Catholic Church, "De Revolutionibus," placing Copernicus' book on the Index [italics mine]:

And whereas it has also come to the knowledge of the said Congregation that the Pythagorean doctrine—which is false and altogether opposed to the Holy Scripture—of the motion of the Earth and the immobility of the Sun, which is also taught by Nicolaus Copernicus in De Revolutionibus Orbium Coelestium...

Here's the punchline: those Church officials interrogating Galileo really believed, with every fiber of their being, that Galileo's assertions were incorrect. They knew the Sun revolved around the Earth. And they were wrong. So, we have Major Lesson Two: Really, really believing in something, and knowing it to be true with all of your heart, does not make it true in actual fact.

The story of evolution is much shorter in time span. Biology did not really develop as a unified study of all living things until Carolus Linnaeus (1707-1778) established his hierarchical system of classification. He placed very similar species into specific categories called "genera," and collected similar genera into broader categories; and he continued in this manner, nesting similar groups into more general groups, forming a repeatedly branching "tree of life." This classification scheme, similar to a genealogical family tree, immediately suggested an explanation for the vast diversity of life. Similar species might be recently descended from a common ancestor; less similar species might share a common ancestor that lived in the more distant past. (In the same way, the common ancestors of siblings—their parents—were born much more recently than the common ancestors of fifth cousins; and siblings tend to be much more alike than are fifth cousins.) Vague notions to this effect had been passed around ever since the ancient Greeks, at least, but the Linnaean system of taxonomy greatly clarified the problem at hand. Ironically, Linnaeus himself was a staunch anti-evolutionist, adhering to the belief in the "creation of separate kinds" as literally described in Genesis.

However, it is one thing to assert that species with similar form are related in some way, and quite another to lay down a theoretical and observational justification for these relationships. At this point, evolution had many of the same problems as the heliocentric theory in the time of the ancient Greeks: a nice idea, but lacking in convincing concrete evidence.

Two concepts prerequisite for a sound evolutionary theory—an ancient Earth and change as an accumulation of small modifications—were developed during the second half of the 18th century. Though he was not the first to do so, James Hutton (1726-1797) carefully cited a wealth of geological evidence that (1) the Earth was much older than the 6,000 years or so indicated by the Bible, and (2) the Earth's internal heat was a major catalyst of slow, large-scale change of the Earth's surface. Decades later, Sir Charles Lyell (1797-1875) expanded and popularized the idea of long-term, gradual change of the Earth, in contrast to the catastrophic changes expounded in the Bible and by certain scientists, notably Georges Cuvier (1769-1832), who, despite his belief in the literal interpretation of Genesis, concluded that the Noachian flood was only the most recent of a series of life-destroying catastrophes.

Using these ideas, several scientists advanced ideas on evolution before Charles Darwin (1809-1882) appeared on the scene, including Darwin's grandfather, Erasmus Darwin (1731-1802). (Oddly enough, the elder Darwin anticipated LiveJournal by over 200 years by setting a significant portion of his scientific writing in the form of horrible poetry.) The first to propose a fully-developed model for the mechanism of evolution was Jean Baptiste Lamarck (1744-1829). He was wrong in the mechanism of evolution, but was correct in citing the two crucial determinants: heritable variation and adaptation to the environment. (Lamarck believed that characteristics acquired during an organism's lifetime were heritable, something that the Jews had actually disproved a couple of millennia beforehand. I'll leave it to you to guess how.)

I won't bore you with a discussion of Darwin's early life; you can find that in any high-school textbook on biology (except in Kansas or Georgia). The important point is that he spent decades developing and refining his theory. His colleagues urged him to publish his findings lest he be scooped by another enterprising biologist, but Darwin wanted to present an airtight case.

As it happened, the young British naturalist Alfred Wallace (1823-1913) independently developed a model for evolution by natural selection, and hesitant to attempt publishing such revolutionary conclusions without an expert's viewpoint, sent his completed manuscript to the eminent biologist, Charles Darwin, for comment. Admirably, Darwin did not attempt to take all the credit for the theory by rushing his own book into publication. Rather, he and Wallace published their work jointly in 1858, somewhat ironically in the Journal of the Linnaean Society.

In the following year Darwin published his masterwork, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, usually and mercifully foreshortened to Origin of Species. A brief look at this book reveals Darwin's painstaking approach.

The book begins with a chapter on artificial selection of domesticated animals, with emphasis on the domestic pigeon, which, under breeding for certain traits by humans, has attained a striking level of diversity, despite the general ability of different varieties to interbreed successfully. All of these different breeds of pigeons are descended from a single wild species, Columba livia. Clearly, selection has brought about a great deal of biological change in a very short time, geologically speaking—and the role of selection is obvious. A modern American reader would be better acquainted with the same situation applied to domestic dogs. Who could imagine that the toy poodle, or any of the obnoxious, ill-tempered yipping machines called terriers, could have occurred in nature? Only a highly abnormal selective process could have produced them.

Subsequent chapters tie in evidence from diverse sources, including mathematics, paleontology, behavioral science, and embryology, to establish the fact that selection has operated in nature, as well, and that common themes unite seemingly unrelated organisms. In the section on embryology, Darwin cites structures that develop in the embryo but disappear before birth, like teeth in certain whales, to infer relationships between diverse groups (in this case, cetaceans and other mammals). Similarly, rudimentary structures, such as the remnants of extra toes in horses, show that horses and similar mammals highly specialized for running are indeed related to more conventional five-toed mammals. These examples punch huge holes in the "creation of different kinds" as a scientific hypothesis. (Of course, they have nothing to say about such creation as a religious hypothesis.)

Darwin also included chapters in which he addressed criticism brought up against the theory. In Chapter VI, under the section "Organs of Extreme Perfection and Complication," Darwin agrees that at first glance, intricate biological structures like the vertebrate eye seem impossible within the context of evolution. He then counters with the statement of Major Lesson One that I quoted above. "Vox populi, vox Dei," indeed. Darwin was well aware of the necessity to separate science from religion, as is any conscientious scientist.

Though nearly scooped by Wallace, Darwin really does deserve most of the credit for working out the theory, on account of the thoroughness of his research and presentation. The Origin of Species is not a book to be read casually; it rather resembles a trial brief for a court case. The reader tends to get lost in the avalanche of detailed examples. But this same exhaustive attention to detail is what makes the theory so strong: it provides a unified explanation for a vast number of observations from every facet of biology. (Amazingly, the published book contained only one-fifth the material that the author originally meant to include.) Darwin was well aware that his book would generate a great deal of indignation in religious circles, and his efforts to present an ironclad argument were largely intended to minimize the potential controversy. Naturally, he failed at this; the Origin of Species caused an uproar in the religious community. (He didn't help matters any by publishing The Descent of Man in 1871.) Many took it as a direct attack on the Christian faith. Even scientists hesitated to embrace Darwinian evolution, so contrary did it seem to their own religious beliefs; but they were hard pressed to find valid objections on scientific grounds.

In summary, Darwin's theory grew from a wealth of precedent in biology and other scientific fields; Darwin developed it using an overwhelming body of evidence in its favor; and he was not alone in arriving at his conclusions. As so it has gone with all important and valid theories. Even Einstein did not derive his Theory of Relativity completely out of the blue, and Einstein was about as revolutionary a thinker as the world has ever seen; in modern times, only Newton can compare.

Darwin gave more than enough evidence for natural selection. However, he left unexplained an important facet of the theory: the nature of the heritable variation among individuals. Here, in fact, was the source of the greatest valid scientific criticism of "descent with modification." The concept of "genes" in the mid-19th century was embryonic. The general perception was that observable traits, such as height or skin color, were genetically "continuous." In other words, parents differing widely in a given characteristic produce offspring intermediate in that characteristic. A mating between a tall and short individual was expected to produce offspring in average height, and in fact generally did. However, this blending of heritable characteristics, if allowed to proceed for a long period of time without significant natural selection, would eventually produce a homogeneous population of individuals who were "average" in every respect. How can productive evolution occur if every population is doomed to universal mediocrity? This weakness in the theory greatly bothered Darwin, and he acknowledged that a weakness existed, but he did not find a solution.

Darwin was unaware of it, but an explanation was available during his lifetime, in the work of the Austrian monk Gregor Mendel (1822-1884). While growing his now-famous pea plants, Mendel noted that certain characteristics—plant height, seed color, etc.—did not combine and average when plants bearing different traits—tall plants vs. short plants, green seeds vs. yellow seeds, etc.—were interbred. Instead, the offspring of true-breeding plants sometimes precisely resembled one parent in a particular character, with the trait of the other disappearing completely. Yet when the progeny of these crossed plants were interbred, the missing trait would suddenly reappear, in full force, in a certain fraction of the offspring. The blending hypothesis was clearly incorrect. Mendel's pea plants exhibited "discrete characters": traits that retain their separate identities despite being combined with, and perhaps masked by, other traits. A population carrying a discrete character is not destined for universal mediocrity: individuals express one variation (trait) or the other, but not a combination of both.

Mendel owned a copy of the Origin of Species, and may well have understood the relevance of his work to Darwin's theory, but made no attempt to contact Darwin. Instead, looking for a well-respected sponsor, he sent his findings to a prominent botanist, Karl Wilhelm von Nägeli (1817-1891), who proceeded to ignore them—thereby making one of the most disastrous mistakes in the history of science. Disheartened by von Nägeli's lack of interest, Mendel published his findings in the Transactions of the Brünn Natural History Society in 1865, and retired from research. His pioneering work remained in complete obscurity until the dawn of the 20th century, when three scientists almost simultaneously discovered his paper—and caused a revolution in biology. Mendel's discrete characters provided the missing piece of the puzzle!

Even though uncounted variations in the Mendelian model have since been discovered, the basic premise remains valid to this day, as does its support of Darwinian evolution.

(An aside: Some traits, including height and skin color in humans, appear to be governed by a large number of genes, each of which exert a small effect. An interaction of many such genes does indeed give the appearance of continuity, especially when the environment can also affect the trait. However, a couple of average height can still have a tall child if the child is fortunate enough to inherit a majority of "tall" genes from both parents. So the blending hypothesis does apply, after a fashion, in certain circumstances, but the genes determining continuous traits are still inherited in Mendelian fashion.)

Once Mendel's work was made widely known, no educated, thinking person doubted the basic fact of evolution. Much discussion continued about the details of the process, and it still does today, but none of this debate about the particulars has invalidated the basic premise. To the contrary, refining and extending the theory has incalculably strengthened it, by bringing diverse fields of biology recently arisen to prominence, such as genetics and molecular biology, under its umbrella. To use a word I usually employ in a negative context: Evolution is the fundamental theory of biology. Biology makes no more sense, in the absence of evolution, that does astronomy in the absence of the heliocentric model of the Solar System.

And yet, we still have poor, misguided fools in the most technically advanced nation on Earth, bitterly opposing the teaching of biology's most fundamental principle in our public schools. Why? Because—say it with me now—it contradicts the Bible. These people have completely ignored the last 400 years of scientific history: they refuse to see the patently obvious connection between Galileo's struggle to promote the heliocentric theory, the truth of which even the Fundamentalists will now acknowledge, and the battles that modern biologists must fight to keep the theory of evolution by natural selection in our schools' biology curricula.

At first glance, matters do not look quite as bleak as the Gallup poll might indicate. Despite his status as Public Enemy No. 1 with respect to world population control and the world's poor, John Paul II performed two admirable acts, with respect to science, during his tenure as Pope. First, he publicly exonerated Galileo of any wrongdoing—a mere 350 years after Galileo's interrogation under the Inquisition. Check it out: this is tantamount to the Catholic Church's admitting, officially, that the Earth revolves around the Sun, and it only took until 1993—a mere 30 years after humankind began sending probes from the Earth to the Moon and the planets, an achievement that would have been completely impossible without the heliocentric model. Who says the Church isn't progressive, eh?

The second was, in 1996, to come right out and state that the theory of evolution was not inconsistent with the Bible. John Paul II was determined not to repeat the Church's mistakes of past, and for that he should be applauded.

Now if we can only convince the fundamentalist Protestants that the Pope made a wise decision! I mean, come on, if even the Catholic Church—that mainstay of Christian conservatism—has capitulated on the issue of evolution, then maybe those Baptists can catch a clue. Alas, it is not to be. Part of the problem clearly stems from the highly negative view of Catholicism that many Fundamentalists seem to cherish, for some inadequately explained reason.

In any case, we currently see, in this modern age, (formerly) competent scientists, such as Henry Morris of the Institute of Creation Research, dedicating their lives to convincing the American public that the theory of evolution is a pack of lies and the root of everything, both real and imagined, that plagues American society. The truly disturbing aspect of this movement is that the creationists allege to be using science to "prove" their pre-existing conclusions about the literal words of Genesis. And you know what? They're wrong!

In the second part, I will examine the relative benefit to society of evolution and creationism, as well as a critical look at the infallible word of God in the King James Version of the Bible.
Tags: astronomy, essay, evolution

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