What is evolution? Why do some people claim it is false? This short essay tries to make it clear why evolutionary science is often unjustly accused of being 'false' or 'untrue', or 'just a theory'. Actually, it is a well-accepted fact.
Most people do not really know what evolutionary science is; ... they rely on popular accounts, what someone else told them, or misconceptions, and base their beliefs on this erroneous information.
It is difficult to even get a proper explanation if you look for it! Standard dictionaries are the worst place to look:
"evolution: ...the doctrine according to which higher forms of life have gradually arisen out of lower.." - Chambers
"evolution: ...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny" - Webster's
These definitions are simply wrong! Unfortunately it is common for non-scientists to discuss evolution using just such definitions. When someone claims that they 'don't believe in evolution', they can't be referring to an acceptable scientific definition of evolution, because that would be denying something which is easy to demonstrate. It would be like saying that they don't 'believe' in gravity!
The real problem is that the public, and creationists, do not understand what evolution is all about. Once we realize that evolution is simply "a process that results in heritable changes in a population spread over many generations" it seems a little silly to pretend that this doesn't happen!
The five ideas below seem to be the most common misconceptions. If you hear anyone making any of them, chances are excellent that they don't know enough about the real theory of evolution to make informed opinions about it.
Evolution is only a theory; it hasn't been proved.
Evolution has never been observed.
Evolution violates the 2nd law of thermodynamics.
There are no transitional fossils.
The theory of evolution says that life originated, and evolution proceeds, by random chance.
Explanations of why these statements are wrong are given below.
"Evolution is only a theory; it hasn't been proved."
First, we should clarify what "evolution" means. It has more than one meaning. Biologically, it means "a change in allele frequencies over time." By that definition, evolution is an indisputable and observable fact. Most people seem to associate the word "evolution" mainly with common descent, the theory that all life arose from one common ancestor. Many people believe that there is enough evidence to call this a fact, too. However, common descent is still not the theory of evolution, but just a fraction of it (and a part of several quite different theories as well). The theory of evolution not only says that life evolved, it also includes mechanisms, like mutations, natural selection, and genetic drift, which go a long way towards explaining how life evolved.
Calling the theory of evolution "only a theory" is, strictly speaking, true, but the idea it tries to convey is completely wrong. There is a confusion between what "theory" means in informal usage, and in a scientific context. A theory, in the scientific sense, is "a coherent group of general propositions used as principles of explanation for a class of phenomena" [Random House American College Dictionary]. The term does not imply 'tentativeness' or 'lack of certainty'. Generally speaking, scientific theories differ from scientific laws only in that laws can be expressed more compactly. Being a theory implies self-consistency, agreement with observations, and usefulness. (Creationism fails to be a theory mainly because of the last point; it makes few or no specific claims about what we would expect to find, so it can't be used for predicting anything. When it does make predictions, they prove to be false.) Find out more about what a theory in science really is here.
Lack of proof isn't a weakness, either. On the contrary, claiming that conclusions are infallible is ridiculous, as has been shown by the past several centuries of scientific reasoning. Nothing in the real world has ever been rigorously proved, or ever will be. In the real world, we must deal with levels of certainty based on observed evidence. The more and better evidence we have for something, the more certainty we assign to it; when there is enough evidence, we label the something a fact, even though it still isn't 100% certain, or fully understood. Many non-scientists don't understand this; creationists use it as an argument against the 'theory' of evolution, which is ridiculous ... you might as well argue that gravity is a theory (it is far from being completely understood), and that we can't assume objects will always fall to the ground. Again, see our Theories in Science page if you aren't sure what we mean.
It is a FACT that the earth, with liquid water, is more than 3.6 billion years old. It is a FACT that cellular life has been around for at least half of that period, and that organized multicellular life is at least 800 million years old. It is a FACT that major life forms now on earth were not at all represented in the past. There were no birds or mammals 250 million years ago. It is a FACT that major life forms of the past are no longer living. There used to be dinosaurs and Pithecanthropus, and there are none now. It is a FACT that all living forms come from previous living forms. Therefore, all present forms of life arose from ancestral forms that were different. Birds arose from nonbirds and humans from nonhumans. No person who pretends to any understanding of the natural world can deny these facts any more than she or he can deny that the earth is round, rotates on its axis, and revolves around the sun. There is evidence in the ground, and in cave paintings, and in our own DNA.
Since Darwin's time, massive additional evidence has accumulated supporting the fact of evolution - that 'all living organisms present on earth today have arisen from earlier forms in the course of earth's long history'. Indeed, 'all of modern biology is an affirmation of this relatedness of the many species of living things and of their gradual divergence from one another over the course of time'. Since the publication of The Origin of Species, the important question, scientifically speaking, about evolution, has not been whether it has taken place. That is no longer an issue among modern biologists. Today, the central and still fascinating questions for biologists concern the mechanisms by which evolution occurs.
What evolution has is what any good scientific claim has--evidence, and lots of it. Evolution is supported by a wide range of observations throughout the fields of genetics, anatomy, ecology, animal behavior, paleontology, cellular biology, and others. There is the agreement among many different dating methods pointing to an old earth and life on earth for a long time; for example: radioactivity, tree rings, ice cores, corals, supernovas - from astronomy, biology, physics, geology, chemistry and archeology. These methods are based on quite distinct fields of inquiry and are quite diverse, yet manage to arrive at quite similar dates.
If you wish to challenge the theory of evolution, you must address that evidence. You must show that the evidence is either wrong or irrelevant, or that it fits another theory better. Of course, to do this, you must know both the theory and the evidence.
"Evolution has never been observed."
Biologists define evolution as a change in the gene pool of a population over time. One example is insects developing a resistance to pesticides over the period of a few years. Even most creationists recognize that evolution at this level is a fact. What they don't appreciate is that this rate of evolution is all that is required to produce the diversity of all living things from a common ancestor!
The origin of new species by evolution has also been observed, both in the laboratory and in the wild. See, for example, (Dobzhansky, T. and O. Pavlovsky. 1971. "Experimentally created incipient species of Drosophila." Nature. 230:289-292).
Even without these direct observations, it would be wrong to say that evolution hasn't been observed. Evidence isn't limited to seeing something happen before your eyes. Evolution makes predictions about what we would expect to see in the fossil record, comparative anatomy, genetic sequences, geographical distribution of species, etc., and these predictions have been verified many times over. The number of observations supporting evolution is overwhelming.
Consider first how evolutionists interpret similarities between species living today. Present-day humans and chimpanzees, despite obvious external and behavioral differences, have extremely similar internal organs and physiological functions; indeed their genes are more than 98% identical. Just as the resemblance between two siblings suggests a common parentage, resemblance between species suggests common ancestors. Evolutionists believe that humans, gorillas, and chimpanzees evolved from a common ancestor: an ape-like creature that lived perhaps five to ten million years ago, rather recently on the geological time scale. Species less similar to humans than are apes--mice, for example--are believed to have branched off millions of years earlier from a common primitive mammalian ancestor. Evolutionary family tree diagrams that express such relationships between species have been constructed by evolutionary biologists by analyzing similarities of present-day organisms. In many cases, fossilized remains of extinct species can be used to support the features of such evolutionary trees.
What hasn't been observed is one animal abruptly changing into a radically different one, such as a frog changing into a cow. This is not a problem for evolution because evolution doesn't propose occurrences even remotely like that. In fact, if we ever observed a frog turn into a cow, it would be very strong evidence against evolution.
"Evolution violates the 2nd law of thermodynamics."
This shows more a misunderstanding about thermodynamics than about evolution. The second law of thermodynamics says, "No process is possible in which the sole result is the transfer of energy from a cooler to a hotter body." Now you may be scratching your head wondering what this has to do with evolution. The confusion arises when the 2nd law is phrased in another equivalent way, "The entropy of a closed system cannot decrease." Entropy is an indication of 'unusable' energy, and often (but not always!) corresponds to what we might think of as disorder or randomness. Creationists thus misinterpret the 2nd law to say that things invariably progress from order to disorder, and never the reverse.
However, they neglect the fact that life is not a closed system. The sun provides more than enough energy to drive things. If a mature tomato plant can have more usable energy than the seed it grew from, why should anyone expect that the next generation of tomatoes can't have more usable energy still? Creationists sometimes try to get around this by claiming that the information carried by living things lets them create order. However, not only is life irrelevant to the 2nd law, but order from disorder is common in nonliving systems, too. Snowflakes, sand dunes, tornadoes, stalactites, graded river beds, and lightning are just a few examples of order coming from disorder in nature; none require an intelligent program to achieve that order. In any system with lots of energy flowing through it, you are almost certain to find order arising somewhere. If 'order from disorder' is supposed to violate the 2nd law of thermodynamics, why does it happen so often in nature?
The thermodynamics argument against evolution displays a misconception about evolution as well as about thermodynamics, since a clear understanding of how evolution works should reveal major flaws in the argument. Evolution says that organisms reproduce with only small changes between generations. For example, animals might have appendages which are longer or shorter, thicker or flatter, lighter or darker than their parents. Occasionally, a change might be on the order of having four or six fingers instead of five. Once the differences appear, the theory of evolution calls for 'differential reproductive success'. For example, maybe the animals with longer appendages survive to have more offspring than the others. All of these processes can be observed today. They obviously don't violate any physical laws.
"There are no transitional fossils."
A transitional fossil is one that looks like it's from an organism intermediate between two different creatures. To say there are no transitional fossils is simply false. Paleontology has progressed a bit since Origin of Species was published, uncovering thousands of transitional fossils. The fossil record is still spotty and always will be; erosion and the rarity of conditions favorable to fossilization make that inevitable.
Also, transitions may occur in a small population, in a small area, and/or in a relatively short amount of time; when any of these conditions hold, the chances of finding the transitional fossils millions of years later goes down. Still, there are still many instances where excellent sequences of transitional fossils exist. Some notable examples are the transitions from reptile to mammal, from land animal to early whale, and from early ape to human.
The misconception about the lack of transitional fossils is aggravated by the way we think about species. When people think about a category like "dog" or "ant," they often subconsciously believe that there is a well-defined boundary around the category. Actually, categories are man-made and artificial. Nature is not constrained to follow them, and doesn't.
"The theory of evolution says that life originated, and evolution proceeds, by random chance."
There is probably no other statement which is a better indication that the arguer doesn't understand evolution. Chance certainly plays a large part in evolution, but this argument completely ignores the fundamental role of natural selection, and selection is the very opposite of chance. Chance, in the form of mutations, provides genetic variation, which is the raw material that natural selection has to work with. From there, natural selection sorts out certain variations. Those variations which give greater reproductive success to their possessors (and chance ensures that such beneficial mutations will be inevitable) are retained, and less successful variations are weeded out. When the environment changes, or when organisms move to a different environment, different variations are 'selected' (ie: those with the variation succeed in reproducing more often than those without it), leading eventually to different species. Harmful mutations usually die out quickly, so they don't interfere with the process of beneficial mutations accumulating.
Nor was the origin of the very first 'life' due purely to chance. Atoms and molecules arrange themselves not purely randomly, but according to their chemical properties. In the case of carbon atoms especially, this means complex molecules are sure to form spontaneously, and these complex molecules can influence each other to create even more complex molecules. Once a molecule forms that is approximately self-replicating, natural selection will guide the formation of ever more efficient replicators. The first self-replicating object didn't need to be as complex as a modern cell or even a strand of DNA. Some self-replicating molecules are not really all that complex at all. Moreover, the molecules build on one another; life didn't spring into being overnight, but was the end result of millions of years of chemical bonding that created, one after the other, larger and more complicated molecules
Click to view image: '38193-darwin.gif'
|Liveleak on Facebook|