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Refuting Creationist Arguments
Creationists explain the existence of diverse organisms and their characteristics as miracles: as the result of direct supernatural intervention. It is impossible to predict miracles or to do experiments on supernatural processes, so creationists do not do original research in support of their theory. (About the only quasi-exception to this statement was their claim to have found commingled human and dinosaur footprints in fossilized sediments in a riverbed in Texas, supposedly showing that these organisms were contemporaneous. Even most creationists now acknowledge that the "human" prints are a mixture of fraudulent carvings and natural depressions.) Thus "creation science," rather than providing positive evidence of creation, consists entirely of attempts to show that biological phenomena must, by default, be the products of intelligent design. Here are some of the most commonly encountered creationist arguments, together with capsule counterarguments.
1. Evolution is outside the realm of science because it cannot be observed.
Most of science depends not on direct observation, but on testing hypotheses against the predictions they make. The structure of DNA, for instance, is known from data that conformed to predictions in the Watson-Crick model, and has still not been directly observed. Besides, although we have not observed, and cannot expect to observe, the origin of new higher taxa, modest evolutionary changes of characters have been observed in many species, new species of plants have arisen within the last century, and natural allopolyploid species of plants have been "re-created" by hybridizing diploid species.
2. Evolution cannot be proved.
Nothing in science is ever absolutely proved. "Facts" are hypotheses in which we can have very high confidence, because of massive evidence in their favour and the absence of contradictory evidence. Abundant evidence from every area of biology and paleontology supports evolution, and there exists no contradictory evidence.
3. Evolution is not a scientific hypothesis because it is not testable: no possible observations could refute it.
Many conceivable observations could refute or cast serious doubt on evolution, such as finding incontrovertibly mammalian fossils in incontrovertibly Pre-Cambrian rocks. In contrast, any puzzling quirk of nature could be attributed to the inscrutable will and infinite power of a supernatural intelligence, so creationism is untestable.
4. The orderliness of the universe, including the order manifested in organisms' adaptations, is evidence of intelligent design, just like the orderliness of a machine designed for a particular function.
Order in nature, such as the structure of crystals, arises from natural causes, and is not evidence of intelligent design. The order displayed by the correspondence between organisms' structuress and their functions is the consequence of natural selection acting on genetic variation, as has been observed in experimental and natural populations.
5. Evolution of greater complexity violates the second law of thermodynamics, which holds that entropy (disorder) increases.
The second law applies only to closed systems, such as the universe as a whole. Order and complexity can increase in local, open systems due to an influx of energy. This is evident in the development of individual organisms, in which biochemical reactions are powered by energy derived ultimately from the sun.
6. It is almost infinitely improbable that even the simplest life could arise from nonliving matter. The probability of random assemply of a functional nucleotide sequence only 100 bases long is 1/4100, an exceedingly small number. And scientists have never synthesized life from nonliving matter.
It is true that a fully self-replicating system of nucleic acids and replicase enzymes has not yet arisen from simple organic constituents in the laboratory, but the history of scientific progress shows that it would be foolish and arrogant to assert that what science has not accomplished in a few decades cannot be accomplished. Critical steps in the probable origin or life, such as abiotic synthesis of purines, pyrimidines, and amino acids and self-replication of short RNAs have been demonstrated in the laboratory. And there is no reason to think that the first self-replicating or polypeptide-encoding nucleic acids had to have any particular sequence. If there are many possible sequences with such properties, the probability of their formation rises steeply. Moreover, the origin of life is an entirely different problem from the modification and diversification of life once it has arisen. Knowledge of the latter does not require knowledge of the former.
7. Mutations are harmful, and do not give rise to complex new adaptive characteristics.
Most mutations are indeed harmful, and are purged from populations by natural selection. Some, however, are beneficial, as shown in many experiments. Complex adaptations usually are based not on single mutations, but on combinations of mutations that jointly or successively increase in frequency due to natural selection.
8. Natural selection merely eliminates unfit mutants, rather than creating new characters.
"New" characters, in most cases, are modifications of pre-existing characters, altered in size, shape, developmental timing, or organization. This is true at the molecular level as well. Natural selection "creates" such modifications by increasing the frequency of alleles at several or many loci so that combinations of alleles, initially improbable because of their rarity, become probable. Observations and experiments on both laboratory and natural populations hav edemonstrated the efficacy of natural selection.
9. Chance could not produce complex structures.
This is true, but natural selection is a deterministic, not a random, process. The random processes of evolution, mutation and genetic drift, do not in themselves result in the evolution of complexity, as far as we know. Indeed, when natural selection is relaxed, complex structures, such as the eyes of cave-dwelling animals, slowly degenerate, due in part to fixation of neutral mutations by genetic drift.
10. Complex adaptations such as wings, eyes, and biochemical pathways could not have evolved gradually because the first stages would not have been adaptive. The full complexity of such an adaptation is necessary, and this could not arise in a single step by evolution.
The response to this common objection has two parts. First, many such features, such as hemoglobins and eyes, do show various stages of increasing complexity among different organisms. "Half an eye" - an eye capable of discriminating light from dark, but incapable of forming a focused image - is indeed better than none. Second, many structures have been modified for a new function after being elaborated to serve a different function.
11. If an altered structure, such as the long neck of the giraffe, is advantageous, why don't all species have that structure?
This naive question ignores the fact that different species and populations have different ecological niches and environments, for which different features are adaptive.
12. If gradual evolution had occurred, there would be no phenotypic gaps among species, and classification would be impossible.
Many disparate organisms are connected by intermediate species, and in such cases, classification into higher taxa is indeed rather arbitrary. In other cases, gaps exist because of the extinction of intermediate forms.
13. The fossil record does not contain any transitional forms representing the origin of major new forms of life.
This very common claim is flatly false, for there are many such intermediates. Creationists sometimes use rhetorical subterfuge in presenting this argument, such as definining Archeopteryx as a bird because of its feathers, and then claiming that there are no known intermediates between reptiles and birds.
14. The fossil record does not objectively represent a time series, because strata are ordered by their fossil contents, and then are assigned different times on the assumption that evolution has occurred.
Even before The Origin of Species was published, geologists who did not believe in evolution recognized the temporal order of fossils that are characteristic of different periods, and named most of the geological periods. Since then, radioactive dating and other methods have established the absolute dates of geological strata.
15. The similarities among organisms that biologists ascribe to common ancestry - i.e., to homology - are actually examples of common designe used by the Creator.
Anything can be "explained" by the will of an omnipotent Creator, but we have no way to obtain information about the Creator, and no way to test this hypothesis. Certainly, many homologous features make no adaptive sense (e.g., gill slits in both fishes and mammalian embryos) and are hard to envision as the products of an optimal, intelligent design. Evolutionary theory predicts that the degree of similarity between homologous features should generally decline with time since common ancestry, and this is generally the case.
16. Vestigial structures are not vestigial, but functional.
According to creationist thought, an intelligent Creator must have had a purpose, or design, in each element of his creation. Thus all features of organisms must be functional. For this reason, the existence of adaptations is not a strong argument for evolution. However, non-functional and even maladaptive structures are expected if evolution is true, especially if a change in an organism's environment or way of life has rendered them superfluous or harmful. Organisms display many such features at both the morphological and molecular level.
17. There are no fossil intermediates between apes and humans; australopithecines were merely apes. And there exists an unbridgeable gap between humans and all other animals in cognitive abilities.
The array of fossil hominids shows numerous stages in the evolution of posture, hands and feet, teeth, facial structure, brain size, and other features. The mental abilities of humans are indeed developed to a far greater degree than in other species, but many of our mental faculties seem to be present in more rudimentary form in other primates and mammals. Both functional and nonfunctional DNA sequences are extremely similar between humans and African apes.
18. Disagreements among evolutionary biologists show that Darwin was wrong. Even prominent evolutionists have abandoned the theory of natural selection, and the entire study of evolution is in disarray.
Disagreements among scientists exist in every field of inquiry, and are in fact the fuel of scientific progress. They stimulate research, and are a sign of vitality. Creationists misunderstand or misinterpret evolutionary biologists who have argued (a) that the fossil record displays abrupt shifts rather than gradual change (punctuated equilibrium); (b) that many characteristics of species may not be adaptations; (c) that evolution may involve mutations with large effects as well as those with small effects; and (d) that natural selection does not explain certain major events and trends in the history of life. In fact, none of the evolutionary biologists who hold these positions deny the central proposition that adaptive characteristics evolve by the action of natural selection on random mutations. All these debates arise from different opinions on the relative frequency and importance of factors known to influence evolution: large-effect vs. small-effect mutations, genetic drift vs. natural selection, individual selection vs. species selection, adaptation vs. constraint, and so forth. These arguments about the relative importance of different processes do not at all undermine the strength of the evidence for the historical fact of evolution - i.e., descent, with modification, from common ancestors. On this point, there is no disagreement among evolutionary biologists.
-- From Evolutionary Biology by Douglas J. Futuyma
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