EVOLUTION: FACT OR PHILOSOPHY?
by Jan Young
CHAPTER 7: TRANSITIONAL FORMS
THE CASE FOR EVOLUTION
According to the theory of evolution, all life descended from the first single-celled organism, resulting in the diversity of life forms on the earth today, as well as the many forms that have suffered extinction. We have seen that some scientists believe it happened slowly and gradually, one mutation at a time. Others believe that periodically, rapid branching occurred, in the form of large jumps. Whichever way it took place, an unbroken line of descent connects the first single-celled organism with the highest organisms, humans.
The organisms that are located on the family tree in between the various distinct types are called transitional forms, or intermediate forms. Any book on evolution will tell you that there are many documented examples of transitionals. The fossil record is full of transitional forms.
"The continuity of the fossil record, even in its present form, proves that man did, in fact, arise out of simpler and less intelligent animals by a succession of minute improvements over hundreds of millions of years." (Robert Jastrow)
"There are an immense number of transitional forms, and museums are overflowing with them...There are even living transitional forms between vertebrates and invertebrates." (Isaac Asimov)
THE FAMILY TREE
Most of us have a record, in a baby book or a family Bible, of our family tree. This enables us to trace our ancestry back through our parents, grandparents, great-grandparents or further. Some people even have family trees that accurately record several hundred years of family history.
The family tree of evolution goes back several billion years. The only record we have of it is found in the rocks--the fossil record. According to the fossil record, humans are descended from pre-human creatures called hominids, which are descended from hominoids, which are descended from anthropoids. Anthropoids are primates, a group that includes both humans and apes. Humans did not exactly evolve from apes, but humans and apes have a common ancestor. The descendants of this common ancestor branched into two separate lines, one leading to apes and one leading to humans.
Primates are members of the group called mammals, which descended from reptiles. Reptiles also branched into two lines, one leading to birds, the other leading to mammals. Reptiles descended from amphibians, the first animals to begin living on land. Amphibians descended from advanced fishes with jaws, which descended from primitive jawless fishes. These primitive fishes were the first vertebrates, or animals with backbones. They descended from invertebrates (animals without backbones) known as echinoderms (ee-KINE-o-derms), which descended from arthropods. Arthropods descended from mollusks, which descended from simple sea animals called sponges.
The earliest life forms were very simple and evolved into more and more complex organisms. As discussed in Chapter 3, the first single-celled life form must have somehow originated from non-living chemicals, apparently in the ocean. Single-celled organisms evolved into multi-celled organisms. Water creatures evolved into land-dwellers. Plant and animal life branched into two different directions. The first plants to live on land were the mosses and ferns, which evolved into all the other kinds of plants.
EXAMPLES OF TRANSITIONAL FORMS
The coelacanth (SEE-luh-kanth) is a kind of ancient fish once thought to be extinct, and is transitional between fishes and amphibians. The lungfish also has characteristics of both fishes and amphibians. Peripatus, which resembles a small caterpillar, is an intermediate form between arthropods and annelid worms. Seymouria is a fossil amphibian with some characteristics of reptiles.
The order Therapsida contains a number of creatures with characteristics of both reptiles and mammals, based especially on the jaw structure. The duck-billed platypus has reptilian and mammalian features. Archaeopteryx, an intermediate between reptiles and birds, is perhaps the most well-known transitional fossil form.
Many candidates for the ape-to-man connection have come and gone over the years. Perhaps the ape-like creatures known as Australopithecines, and classified as hominids, are currently the most well-accepted. A great deal of attention has been paid to a hominid fossil discovered by Donald Johanson and his team in 1974 and classified as Australopithicus afarensis, but nicknamed "Lucy." Time magazine (March 14, 1994) claims that Lucy is the "missing link," and was an animal with human characteristics. In the field of human evolution, new discoveries are being made all the time, and are being fit into the family tree.
PROBLEMS WITH EVOLUTION
In Chapter 3, we discussed the impossibility of life originating from non-life. This all-important transition is undocumented in the fossil record and, as of this writing, has not been proven by laboratory experiments. Proof of the transition from non-life to life is absolutely crucial to the theory of evolution. It is difficult to understand how the theory has survived this long without it.
In the same chapter, it was demonstrated that the simplest single-celled organism is far from simple. Its complex structure and function demands that many transitional forms of life must have led up to it, yet there is evidence of none. The gap between single-celled and multi-celled organisms is even greater, and is also unbridged by intermediate forms. Now let's talk about the possibility of transitional forms between the various biological divisions of life.
1. The Argument of Logic
If evolution is true, the fossil record should be full of transitional forms. In fact, there should be no distinct species, today or in the fossil record. Since all species should be overlapping and blending into other forms, biological classification should be impossible. All organisms should be in a state of transition.
Instead, we see that all organisms fall into distinct, separate classes. Why?
If one mutation took place in the direction of a new species, "nature" would not be able to distinguish that this small change needed to be followed by many more changes before the creature was a fully-adapted new species. Nature would have selected this change because it resulted in an organism that was already better adapted than the previous form, and therefore capable of complete, normal function without any further change. Nature could have no idea of the concept of "transitional" unless nature is some entity with knowledge of the future and plans for the future of each organism. The concept of "transitional" is an artificial concept that has been imposed on the fossil record.
If evolution happened through a long string of beneficial mutations, then all forms should be transitional. Yet it is totally impossible that a transitional form could exist. As we saw in Chapter 6, any change from a complete, mature, fully functioning form in the direction of a different form, would fall into the category of a mutational monster. Darwin said, "Natural selection tends only to make each organic being as perfect as, or slightly more perfect than" similar beings.
For example, a fish's gill becoming a better gill is one thing. However, any change from a gill toward a lung could not possibly make the fish better adapted to live in its present environment. Such a mutation would probably be weeded out by natural selection. We saw in the previous chapter that natural selection works toward stasis, not change. There is no way to get from gill to lung by any known natural processes.
If this logic is correct, then Darwin himself admits that his theory is an impossibility.
"If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down."
We have already discussed how natural selection is not capable of bringing about macroevolution. But letís assume it could, as many believe. Natural selection cannot select both the less-adapted form and the new improved form. Only one can be selected. (If both are "selected," then no selection has taken place.) If natural selection favors the higher form, it should leave more offspring. That means that the lower form should leave fewer offspring, and will eventually die out.
Therefore, if all organisms are continually evolving upward, shouldn't all lower forms eventually die out? Shouldn't all organisms except the most advanced have become extinct by now? Should not the world be populated only by mammals? Darwin too asked, why do so many of the lower forms still exist, and why have not the higher forms taken over everywhere?
If earlier forms were inferior, they should have died out when new, better adapted forms evolved. If earlier forms were not inferior, then why did natural selection select new life forms? New forms could not be better if the old forms were not inferior.
Why didn't invertebrates begin dying out when vertebrates evolved? or fish when amphibians evolved? or amphibians when reptiles evolved? or reptiles when mammals evolved? Instead, invertebrates continue to flourish, even though they are less adapted than the vertebrates that evolved from them. Fish are flourishing also, even though the reptiles that evolved from them are better adapted for life. Reptiles are doing quite well today too, living among the mammals who evolved because they are better adapted for life than the reptiles.
In order for natural selection to select organisms with new, partly formed organs and structures, nature would have to select with a different, future environment in mind, an environment in which such new structures would be required. Nature would have to be some sort of benevolent, intelligent force, capable of foreseeing the future, making and carrying out a long-range plan, and working toward the future benefit of each organism. Is this possible?
What is "nature?" Several definitions for "nature" can be found in Webster's New International Dictionary. According to one definition, nature is "the created world in its entirety." But another definition says that nature is "a creative and controlling agent, force, or principle operating in something and determining ... its constitution, development, and well-being," "such a force or agency in the universe acting as a creative guiding intelligence."
These two definitions are quite opposite. In fact, they express two conflicting world views: 1) that nature is created, and 2) that nature is a creative force. It is not the purpose of this book to address this issue, but it is impossible to avoid the issue completely.
Many evolutionists speak of nature's role, or natural selection, as if nature was some sort of intelligent force. Jastrow writes, "Nature set to work immediately to improve those first simple organisms...," and, "Nature wrote the frog's program."
Gould writes along a similar vein: "Apparently, evolution settled upon just a few themes or ground plans for arthropods and then stuck with them..."
An even more forceful statement is found in Creation and Evolution, by Norman Newell. In the front matter is this quote from Ruth Nanda Anshen: "...evolution shows man arisen by a creative power inherent in the universe." Consider this claim by Darwin:
"It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good..."
He argues that to speak of natural selection in this way does not imply it is a power or deity; he is merely using a metaphorical expression (a figure of speech, not to be taken literally).
Evolutionists, as discussed in Chapter 1, have a naturalistic world view. That means that everything can be explained by natural laws and processes; supernatural processes are completely ruled out. "Supernatural" means that which transcends nature, usually referring to God or a god. Yet in order to explain how evolution could have happened, many evolutionists find it necessary to give to nature some of the qualities that we would ordinarily give only to God.
Giving nature the power to plan and direct our ways, always with our ultimate good in mind, is acceptable, whereas giving that power to God is not. Again we see redefining of terms. Nature is no longer simply the world around us, but is now a supernatural force. If nature is supernatural, then what is natural?
Can natural selection be looking out for the good of each creature? Can natural selection, whoever or whatever it is, know which mutations will eventually help the organism to adapt to some future environment? That future environment might be millions of years in the future. Natural laws, such as gravity, don't know or care about good or bad, or future conditions; they just operate.
Not all evolutionists attribute these qualities to nature. Some shy away from stretching the definition of nature to include a benevolent, creative power. However, without that power, natural selection, if it was even able to bring about evolutionary change, is incapable of selecting for traits that will only benefit the organism in the future, after it has fully made the transition to a higher form.
2. Do Transitional Forms Exist?
The gaps in the fossil record existed in Darwin's day, but he had high hopes that as more fossils were discovered, the gaps would be filled in. This has not turned out to be so. The gaps are just as obvious. Denton claims that transitional forms between the major groups are not just missing; it is virtually impossible to scientifically explain, or even imagine, their existence.
Plants appear suddenly in the fossil record. Invertebrates (animals without backbones) appear suddenly in the fossil record, with no evidence of evolution. Neither is there fossil evidence for the evolution of vertebrates. As for insects, there is no fossil record of any ancestors.
It is not enough to claim, as many books do, that one group evolved, or probably evolved, or may have evolved, from another group. That is ducking the question of transitional forms. The Darwinian line of descent requires that an individual is ancestral to another individual. If an unbroken line of descent, or even a major portion of it, cannot be demonstrated, then the theory of evolution is far from being proven.
Today there are fewer examples of transitional forms than there used to be. As further research has been done on organisms once thought to be transitional, some have been definitely disqualified from that category. Sometimes the "ancestor" is later found in the same strata as its "descendant." If they lived about the same time, there is then no reason to believe that one was ancestral to the other.
The fossil horse series is an example of transitional forms that have been disqualified by further research, as discussed in Chapter 4. And even if Eohippus and the others were actual ancestors of the modern horse, they could not be considered as transitional in the process of macroevolution. The horse series is about microevolution--a primitive horse changing into a modern horse.
3. Frequently Cited Transitionals
Is the coelacanth (SEE-luh-kanth) an intermediate between fish and amphibian, as some claim? In 1938 a live coelacanth was found in the Indian Ocean, upsetting the notion that it was extinct. Fossil coelacanths appeared to be closely related to amphibians, based on their skeletal structure, which is all that was fossilized. Biologists were surprised to find that internal soft body parts did not at all resemble amphibians. They did not appear to be intermediate between fishes and amphibians.
Is Seymouria a true intermediate between amphibians and reptiles? It shows characteristics of both. But it appears too late in the fossil record to qualify as an ancestor to the reptiles.
Is the lungfish an intermediate between fish and amphibian? It does have several characteristics of each, but each specific trait is fully developed and functional. It does not show any traits in the process of forming. The gills and fins are like those of any normal fish, and the lungs and heart are like those of a normal amphibian.
Is Peripatus an intermediate between arthropods and annelid worms? It too has characteristics of each, but none of its traits are in the process of changing, as evolution requires. Its circulatory system and respiratory system are those of an arthropod, and its nervous system and excretory system are those of the annelid worm.
Do the mammal-like reptiles qualify as intermediate forms? The mammal-like reptiles are two reptiles with some characteristics resembling mammals. The important features are the jaws and the ears. Reptiles and mammals have distinctly different jaw bones and ear bones.
The mammal-like reptiles had well-developed, fully-functioning reptile jaw joints. Both also supposedly had a structure that is found only in mammals; this judgment is based on fragments of jaw bones, since no complete jaws have been found. The existence of the mammal-type bone can only be inferred from such fragmentary evidence. Inference is not scientific proof.
Another difference between reptiles and mammals concerns the ear bones. How did this difference come about? According to the theory of evolution, the reptile jaw joint was gradually replaced by the mammal-type jaw. As the reptile jaw gradually ceased to function, its bones somehow became detached, moved to the middle ear, and became mammal-type ear bones. How these bones could have moved and changed has not yet been explained.
Archaeopteryx (ar-kee-OP-tur-iks) is probably the most well-known and frequently cited transitional fossil. It is considered by many to be a proven transitional between reptiles and birds. Because it is such an important fossil, we will look at it in detail.
Archaeopteryx has features of both birds and reptiles. It is mostly birdlike, and somewhat resembles a small dinosaur, Compsognathus. Like a bird, it has wings, feathers, and a wishbone. Like a reptile, it has teeth, and claws on its wings. However, some ancient birds had teeth, and some modern birds have claws, such as the ostrich, the hoatzin (watt-SEEN) of South America, and the touraco (tur-ah-KO) in Africa.
Because fossils only preserve the exterior of an animal, it is impossible to tell from a fossil what the inside of the organism looked like. Denton claims that "ninety-nine per cent of the biology of any organism resides in its soft anatomy, which is inaccessible in a fossil."
However, some conclusions about the brain can be drawn from the fossil by studying the braincase. Archaeopteryx appears to have a bird-like brain, which lends weight to the conclusion that it was fully birdlike in flight. If so, it would have also had a bird-like heart and lungs.
The bird-like characteristics of Archaeopteryx are truly bird-like, and the reptile-like features are truly reptile-like. The feathers are true feathers and the wings are true wings. They do not lie somewhere between scales and feathers, or between limbs and wings. Archaeopteryx sheds no light on how scales evolved into feathers, or limbs into wings. So far nothing at all is known about how scales could gradually form into feathers. There are no fossils with scales that have partly evolved into feathers.
Although Archaeopteryx resembles both reptiles and birds, it does not necessarily follow that it developed through evolution. It may just be one of those many odd creatures that happen to resemble two different types of organisms. As already mentioned regarding the coelacanth, similarity does not prove close relationship.
Many evolutionists, if not the majority, now consider Archaeopteryx to be a true bird. Fossils of modern birds have been found in the same strata as Archaeopteryx in eastern Colorado. This would certainly seem to kill the notion that Archaeopteryx is the ancestor of modern birds. This information is not found in most textbooks. Why?
A few books mention a hypothetical bird ancestor called proavis or protoavis. This imaginary creature has been described by Gerhard Heilman in his book, The Origin of Birds. Since then, a recent fossil find in Texas has actually been named Protoavis. It is mentioned in the 1993 edition of Miller and Levine's high school text, Biology.
"More recently, another transitional fossil--a fossil with both dinosaur features and bird features--has been found. This species, called Protoavis, is older than Archaeopteryx. Protoavis confirms that birds are related to dinosaurs."
Protoavis and Archaeopteryx "document the evolution of birds from ancient reptiles," it is claimed.
Controversy surrounds the fossil called Protoavis. Few critics agree that the crushed bone fragments prove anything. Whether those bones are from a birdlike creature is debatable.
Archaeopteryx is the single fossil that evolutionists can cling to as a possible intermediate form, but it is not universally accepted as transitional.
5. The Missing Link?
Transitional forms are sometimes referred to as "missing links." On the other hand, "The Missing Link" is the name given to the hypothetical fossil that many hope will some day prove beyond a doubt that man descended from animals. Has The Missing Link been discovered?
Back in the 1800s, fossils of Neanderthal Man were thought to be The Missing Link to our pre-human ancestors. But they turned out to be just people. Neanderthal Man was once considered an evolutionary ancestor of modern man, and until recently, was pictured as sub-human, with stooped-over posture, low brow and receding chin. A study published in 1957 revealed that Neanderthals were true humans. Some of their skeletal characteristics were merely the result of bone disease.
In 1891, Dr. Eugene DuBois heralded his fossil find, Java Man, as the Missing Link. Late in his life, DuBois admitted that these were actually unrelated bones of a human and a gibbon. Nearby, in the same strata, he had also found a skull that was definitely human, giving further credence to the fact that these fossils were not those of a pre-human. But many continue to refer to Java Man as one of the fossil forerunners of man.
In 1912, scientists were certain that Piltdown Man was the Missing Link, but over 40 years later, it was revealed to be a hoax. Piltdown Man turned out to be an orangutan jaw that had been combined with a human skull and artificially aged. The jawbone was from an orangutan that had died only 50 years before. Why couldn't the experts tell a 50-year-old bone from a 500,000-year-old fossil, as it was claimed to be?
Another supposed Missing Link, Nebraska Man, was based on a tooth found in 1922, which later turned out to belong to a pig. Other candidates, such as Ramapithicus (ram-a-PITH-i-cus) and Zinjanthropus (zin-JAN-thro-pus), also turned out to be just apes. Past experience warns us not to be too quick to accept new "proofs." No fossil has yet been proven to link man to a non-human ancestor.
Is "Lucy," the fossil discovered by Donald Johanson, really The Missing Link, as Time magazine claims? Those who accept Lucy are those who are already convinced of the ape-to-man transition, and are seeking fossils to prove their belief. But others are much more skeptical. Preconceived ideas about human evolution play a definite role in the interpretation of fossil evidence.
An article in Time, "How Man Began" (March 14, 1994), closes with this candid observation about the study of human evolution.
"The only certainty in this data-poor, imagination-rich, endlessly fascinating field is that there are plenty of surprises left to come."
In other words, the writer believes there isn't much data, or concrete evidence. He also is saying that many scientists are guilty of concocting imaginative, rather than factual, conclusions about their finds.
The theory of evolution requires multitudes of transitional forms, yet solid evidence for their existence has yet to be found. It is impossible to trace the direct descent from any one organism to any other through a series of intermediate forms. Many fossils once held to be transitionals have been eliminated from the game by further research.
Sweeping pronouncements are made about fossil finds immediately upon discovery, before a fossil can be scrutinized, tested repeatedly, and exposed to the critical eye of the worldwide scientific community. Museums are full of fossil reconstructions based not on evidence but on artistís imaginations.
It may be argued that the lack of transitional fossils is no problem to evolution, because evolution happened by large jumps or "rapid branching," as punctuated equilibrium claims. But for this claim to be seriously considered, it must be demonstrated (not just speculated) that some biological mechanism could cause such big jumps, with great numbers of related mutations. Science has not yet demonstrated that this is possible.
Textbooks present evolution as fact. From single-celled organisms to humans, the logical progression is demonstrated of how life evolved. Most of the missing transitions are glossed over by vague statements such as, "this is thought to have evolved from that, about so many million years ago;" "then this evolved, probably from that;" or simply, "then such-and-such evolved."
While it is usually claimed that many transitional forms exist, only a few are mentioned by name. In looking at some of the most frequently claimed transitionals, we have seen that their status is questionable.
Nowhere do we see living transitional forms. No organisms have part of an old organ or limb combined with a new form of organ or limb. Whether the concept of transitional forms is even scientific is open to debate. Has science proven the transition from molecule to man?
Copyright 2003 Jan Young
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