The Origin of Species--Creationism and Evolution
"The plants and animals you just saw live here in the Galapagos Islands. The Galapagos are a chain of what some call the enchanted islands about six hundred miles off the coast of South America in the Pacific Ocean. Charles Darwin visited these islands in 1835 and wrote in his journal that they gave him clues to what he called the mystery of mysteries-the origin of species in our natural world."
In Darwin's day, the early 19th century, a little less than two hundred years ago, most people did not believe that there was a mystery about the origin of species. Most scientists and most laymen believed that each kind of plant and animal was specially created by God to play a particular role in the natural world. Most people in the western world believed further that the natural world itself was created just a few thousand years ago. And most people also believed that there was a universal flood, as described in the Bible that destroyed many species of plants and animals. Those living species that survived in Noah's Ark were the direct ancestors of all the plants and animals that live today.
That view is called creationism, or sometimes today creation science. While it was widely accepted in the early 19th century, it is a view that virtually all scientists today reject as unfounded.
In place of creationism, virtually all scientists today believe that the earth is between four and five billion years old. They believe that over that immensely long period countless mountains have been slowly pushed up from what were once ocean floors. These same mountains then slowly eroded away back to the ocean floor. Catastrophic changes from volcanoes, floods, earthquakes and meteor collisions have changed the surface of the earth time and time again. Whole continents have slowly moved away from one another as the gigantic rock plates on which the continents ride slip over one another a few inches a year.
Layer after layer of sedimentary rock has been built up from the deposits of silt and sand as well as the remains of creatures who lived and died over those billions of years. Geologists point out that you can still see all of these changes on the earth surface, fast and slow, happening today.
Virtually all biologists today are convinced that all present day plants and animals, including human beings, are descended from earlier forms of life in an unbroken tree of life that is itself three to four billion years old. This view is called evolution.
Note I said virtually all scientists are convinced. There are a few scientists-though indeed very few-who disagree with this evolution consensus and still believe, as did their predecessors in the early 19th century, in creation science. A much larger number of non-scientists also believe in creationism.
Let's look at how this important change in our view of life on earth came about. What is the evidence that has convinced the vast majority of the scientific community that evolution itself is not just a theory but a fact? And what is the additional evidence that has convinced them that Darwin's theory of evolution by natural selection is by and large the most well supported theory as to how evolution happened?
Some historical background helps in understanding this great change in our view of life on earth.
Until the 19th century, Darwin's century, very little was known about the facts of natural history. There was very little evidence, in other words, to support any theory about the origin of species.
For one thing, not many species were known. Aristotle, for instance, the greatest scientist of ancient Greece and one of the first to attempt a scientific classification of living things, found room for only about 500 species of animals. As late as 1600 only 6000 species of plants were known.
Fossils were known in ancient and medieval times but they were little studied or understood. The most common view was that they were freaks of nature placed there to amuse or mystify humans. In medieval times some saw fossils as the remains of creatures not able to get on Noah's Ark, and therefore killed in the Biblical flood.
Similarly, little was known about the earth itself. Copernicus, Galileo, and Newton had convinced the educated world (after a great deal of conflict with the church) that the earth did not stand still at the center of the universe, nor did the sun and stars revolve around the earth. But as to the physical structure of the earth and how it got to be the way it was, there was almost total ignorance.
Miners had barely scratched the surface of the earth. Sailors knew of ocean currents and winds and a few sea creatures, but little or nothing about the ocean bottom. Much of the land surface of the earth had not yet been explored or mapped or described in any detail, much less with scientific precision.
Chemistry had not yet been born and no one knew there was such a thing as oxygen or anything about the composition of air.
When Thomas Jefferson, for instance, sent Lewis and Clark on their famous expedition across the United States at the beginning of the 19th century (not quite two hundred years ago), there were still no reliable maps of the Rocky Mountains and the Western United States. One of the most important challenges Jefferson gave to the explorers was to discover what new plants and animals lived in this great unknown American west.
Railroads, steamships and telegraph lines had not yet been invented, so it took over three weeks just to get specimens and descriptions of their discoveries from St. Louis to Washington via rowboat and horseback.
This was the world of knowledge and technology that Darwin was born into in the early 19th century.
As a child and as a young man Darwin himself was an avid amateur naturalist. While he planned to be a clergyman in the Anglican Church there came a chance at the age of 25 to go on a round-the-world voyage as an unpaid naturalist and companion to the captain of HMS Beagle. He snapped up this opportunity to see more of the world of nature that he loved so much.
"One of the places Charles Darwin first stopped to explore on his five year voyage around the world on HMS Beagle was a tropical rain forest like the one behind me. It was of here that he later wrote 'it was like giving a blind man eyes.'"
South American rainforests, he found, were very different from the English gardens, fields and woods he was used to exploring. These mysterious dense tropical forests surprised and delighted him with their incredible diversity of plants and animals. Every time he went ashore he found and collected many new and unusual plants and animals no one had ever described before.
He also found mountains and beaches, plains and deserts, deltas and islands, evidence of volcanoes and earthquakes that no one had ever described in geological detail before. And he found many fossils of animals and plants no one had yet described or studied.
Where had all these marvelous new animals and plants come from? Why were there so many different kinds?
"Like most of his contemporaries, scientists and laymen, in the early 19th century, Charles Darwin was convinced that all living species had been expressly designed by God to play a particular role in the natural world. It was here in South America that he first began to have doubts and to see the possibility of another theory to explain how living things came to be the way they are."
Four years of exploration on the Atlantic and Pacific coasts of South America increased his doubts. And then of all his stops, a five-week stay in the Galapagos Islands, 600 miles west of the continent in the Pacific Ocean, was the most crucial of all to his future life and fame.
What was special about the Galapagos?
"Darwin wrote in his diary `by far the most remarkable feature of this archipelago is that the different islands to a considerable extent are inhabited by a different set of beings.'"
Darwin found, for instance, fourteen different species of small finches-like no other finches in the world-on the islands. Each finch species had a different shaped beak, adapted to find and eat different kinds of food.
Darwin found giant land tortoises. They were similar to some of the land tortoises in nearby South America, but different too. When he looked closer he found that each of the small islands here had a different sub-species of tortoise. These species and sub-species were found nowhere else in the world. There was also a striking, if more distant, similarity to some of the fossils of reptiles that Darwin had found on the South American mainland.
Mockingbirds found on different islands only a few miles apart were different from each other. All the mockingbirds in the Galapagos Islands, on the other hand, were also similar to the mockingbirds of South America six hundred miles to the east-and yet different-different enough to be a different species.
The marine iguanas that carpeted the rocks were also unique to the Galapagos, as were the penguins, the waved albatrosses, and the land iguanas. In fact most of the plants and animals he was finding were what ecologists today call endemic to the Galapagos Islands, that is, they were found nowhere else on earth.
Unlike nearby South America, however, Darwin found no native mammals on the Galapagos Islands. Why not?
"Why are the plants and animals in the Galapagos Islands similar to but very different from the plants and animals of nearby South America? The more Darwin explored, the more his doubts increased."
Creationism said that each living species had been created the way it is found today and had not changed "in kind" since that creation just a few thousand years ago.
Why would God create so many different kinds of animals and plants for each of these small islands? Why did he put so many species of unusual reptiles and birds here, but no mammals?
With his own eyes Darwin had seen an enormously greater number of species of plants and animals in other parts of South America. What of the plants and animals he knew were just now being discovered in Africa, in North America, in Asia and the South Pacific?
How could the ancestors of all of these plants and animals fit in an ark, no matter how big it was? How could they travel to get there? How could they get back after the flood?
And what about the fossils he and others were finding in ever increasing numbers? Some of them were similar to some of the plants and animals he was finding today. Others in the deepest and oldest layers of rock were very different from anything alive today.
Creationism, he realized, did not give a reasonable answer to any of these questions. It merely said God made it so. There must be a better explanation for all the likenesses and differences that he observed among living things.
Darwin was not alone in his explorations and in his doubts. Other naturalists were exploring other parts of the world and finding more and more similarity and more and more diversity in living things-and were asking more and more of the same questions. Another English naturalist, Alfred Russel Wallace, was exploring Southeast Asia and the South Pacific Islands, and not only asking some of the same questions as Darwin, but coming to the same answers.
The answers that Darwin gave to these questions were published some twenty years later in 1859 in his revolutionary book, On the Origin of Species by Means of Natural Selection.
By the time Darwin published his book it was already becoming widely accepted in the scientific world that the earth must be much much older than creationists claimed. The fast growing fossil record showed with increasing certainty that life had been different in past ages, but it also showed that certain common patterns of ancient life structures were remarkably similar to those of today. In short, scientists were more and more certain that the similarities of all living things could be explained by their common ancestry and that the differences among living things could be explained ... ?
Aye, that was the problem.
If all organisms trace back to common ancestors, why aren't they all the same?
No one had yet put forth a reasonable theory to explain how the differences came to be.
Like all good theories in science, the theory of evolution by natural selection was simple and powerful. Here is how living things have changed in the past and are changing today. Here is how that tree of life has grown and branched and flowered.
In nature, said Darwin (and Wallace), living organisms have far more offspring than can possibly survive. The result is a struggle for existence. Since offspring vary, some will be more fit than others to survive in this struggle. These survivors will pass on their useful traits to their offspring.
In time, much as a gardener artificially selects traits he wants in his plants or as a pigeon breeder selects traits he wants in his pigeons, nature will select traits that are advantageous to the individuals who have them.
And in time, nature's selections will result in whole new species of living things! The mystery of mysteries is solved.
"In time" was a crucial phrase in the new theory of evolution by natural selection. Darwin and Wallace recognized that while artificial selection took only a few years or a few decades, natural selection was very slow and would no doubt take many thousands, even millions of years to create a new species.
Here Darwin and Wallace had much new evidence from geology to support their theory. James Hutton in Scotland and Charles Lyell in England had pioneered in putting together new data in geology to show that indeed the earth could not possibly be only a few thousand years old. Their observations and measurements of rock and mineral outcroppings showed that the earth itself was constantly changing in the past and is still changing today.
It was clear that the earth was not thousands, but many many millions of years old.
It all began to come together and to make sense.
As an example, take all of the animals and plants Darwin saw and wondered about in the Galapagos Islands. Evolution by natural selection answered his questions.
The islands, geologists said, were made by volcanoes four to five million years ago. (This time frame is confirmed by many accepted methods in geology today.) In those early days there was no life on the islands at all. However, once the volcanic lava had cooled enough, life began to arrive.
Sometimes from the sea around the islands plants and animals could swim or float and find the beaches and rocks. Some living things could come on drifting logs. Some came on natural sod rafts that still today float down the rivers in Ecuador and out to sea where they pick up the Humboldt Current and arrive three to four weeks later on one of the Galapagos Islands. And some plants and animals could arrive through the air, either blown there on storms from the mainland or on their own power like the sea birds.
Using one or another of these methods some plants, some birds, some insects and some reptiles managed to make the journey successfully. Mammals, however, (except for aquatic mammals like sea lions and fur seals) could not survive any of these transportation routes.
It must have taken a long time for some of these pioneering species of plants and animals to arrive on the islands, to establish a foothold, to find food and above all to successfully reproduce.
A few pairs of South American finches must have first done so - say a million and a half years ago. Plants by then had begun to carpet the islands. Some of them provided seeds that the finches could eat and nesting materials to make reproduction possible.
A million and half years would have seen many variations in the plant populations as rainfall varied from year to year and as competition with other plants and animals changed. Different plants, different seeds, different growth patterns would come along. Since no mammals were there and only a much more limited variety of birds than existed on nearby South America, the original successful finches found new opportunities not available in the South American environment their ancestors had come from
In every living environment, ecologists today use the word "niche" to point to this kind of opportunity. "Niche" means the particular role or job that any organism plays in a given environment.
Thus, in the Galapagos environment, niches taken by mammals in South America, for instance, would be empty and thus open to use by reptiles like iguanas and tortoises and lizards who here had no mammals to compete against.
Niches taken in South America by parrots, toucans, and hundreds of other bird species were empty here and open to use by finches instead-if they had the right equipment to exploit them. In finches this most often meant the right kind of beaks.
Finches with slightly wider beaks, for instance, would have a better chance to survive in certain seasons and on certain islands. Finches with slightly sharper, longer beaks would have a better chance to survive in certain seasons and on certain islands. Isolated on each island over a million and half years, these small changes from year to year would result in the diversity that Darwin found in 1835. No longer just one species, but over 14 separate species of finches, filling up the available niches in the Galapagos ecosystem.
The theory of natural selection did a good job explaining these changes-not only in the Galapagos but everywhere in the world! This, said Darwin, was how and why there were so many different kinds of plants and animals in our living world, and yet how and why they are all similar too-because they all, including human beings, have common ancestors!
A successful theory in science, however, not only explains how things happen, it can be used to direct the way to new knowledge.
"How do you know if a theory is true or not? Every year scientists from around the world come here to the Charles Darwin Research Station in the Galapagos Islands to test the theory of evolution by natural selection."
And in fact in only the last two decades biologists from Princeton University, for instance, have shown conclusively how evolution of Darwin's finches is still going on in these same Galapagos Islands today! With remarkable speed, in fact, new species of finches are today evolving in the Galapagos Islands.
Other biologists here in the Galapagos are finding relationships in the DNA of Galapagos tortoises and the marine and land iguanas, proving their close relationships with South American tortoises and iguanas from whom they evolved some million or so years ago.
And in fact all over the world study after study is showing the power of the theory of evolution in action today.
Medical researchers, for instance, find that the bacteria that cause tuberculosis, pneumonia and other diseases are evolving constantly to form strains that are resistant to antibiotics.
Agricultural scientists find that insects are evolving into new varieties to become immune to our insecticides.
Plants evolve to become immune to modern herbicides.
DNA studies continue to show fascinating relationships among mammals, reptiles, birds and amphibian species, families, orders and phyla.
In short, just as there is no dispute in astronomy that the earth moves around the sun and not vice versa, in the international scientific community, there really is no dispute today about the reality of evolution, in other words about the common ancestry of all living things in the living world. We all indeed do belong to the same tree of life.
Whether the similarities and differences in the tree of life can all be accounted for by Darwin's theory of evolution by natural selection, is still in dispute. Some modern biologists claim, for instance, that the evidence shows changes in the tree are not always as slow and gradual as Darwin proposed. Jumps in the fossil record occur when sudden mutations of genes combine with changes in the environment to produce what Stephen Gould has called "punctuated evolution."
It should be pointed out, however, that while these "jumps" of punctuated evolution do lead to much more rapid change than Darwin assumed, they are still glacially slow in any human time frame. The average species, for instance, lives about 10 million years, and what Gould means by sudden change is one that occurs in the first million years of that species' lifetime!
In other words, scientists debate details of just how the tree of life has grown and branched over the ages but are united in their conviction that the tree is a fact-all living things today have common ancestors in the past.
These disputes in the scientific community are unrelated to the claims of creationists today. In science the overwhelming consensus is clear and strong. Creationism was indeed a theory accepted by many scientists two hundred years ago. However, in the light of all the accumulated evidence since those days it is clear that belief in creationism today is a religious belief but one that has no standing in science.
Does this mean that religion and God have no relevance to life in the past or to life today?
No. It does not mean this.
Many scientists today (like many non-scientists) have strong religious beliefs and find deeper spiritual meanings in life on earth then and now.
There is no necessary conflict, in other words, between a belief in God and a belief in evolution. In fact most modern Christian churches, including the Catholic Church (as recently stated by the Pope), have accepted the facts of evolution as evidenced by modern science and for the most part have accepted Darwin's theory of evolution by natural selection as a reasonable way to explain these facts.
Beyond and behind the long drama of the evolution of life on this earth many thinkers point out there are mysteries not probed by science. These are the mysteries of human consciousness, of the human soul. To explore these mysteries, they point out, science alone is inadequate. To explore these mysteries we may also need art, poetry, music, dance, philosophy and religion.