Repeatable Evolution or Repeated Creation?
Any casual observer of nature recognizes that many creatures bear some resemblance to one another. Many species of frogs, lizards, fish, and other animals and plants from different parts of the world appear to be nearly identical. This similarity has been the pattern throughout life’s history. Recent biological studies have shed light on the nature of this physical resemblance and carry significant apologetic implications. Many species that look identical are, in fact, genetically different, and therefore unrelated. In accounting for these unexpected differences, evolutionary biologists have proffered inadequate explanations. This article will discuss a few of the many recent discoveries that continue to buttress the case for a biblical Creator while continuing to erode the foundation for the evolutionary paradigm.
According to evolutionary theory, organisms that possess identical morphologies (forms or structures) must share a common ancestry. Evolutionary biologists, therefore, have employed morphological systematics––the study of the relationships among organisms according to physical characteristics––when classifying species, and thus have concluded that similar groups share common ancestry. However, with the advent and widespread application of molecular systematics, in which DNA sequences are used instead of morphologies to determine biological relationships, science now is beginning to identify an increasing number of challenges to the evolutionary classification. Biologists are uncovering numerous examples of organisms that cluster together morphologically (structurally), and yet are genetically distinct. Frogs, lizards, or herbs that appear to be identical are actually different at the genetic level. An evolutionary interpretation of this data, then, demands that the morphologically identical organisms must have evolved independently of one another in a “repeatable” fashion.
The Contingent Nature of the Evolutionary Process
The evolutionary paradigm cannot accommodate “repeatable” evolution. When evolutionists observe a tree frog ideally suited for its environment, they assert that natural selection––environmental, predatory, and competitive pressures repeatedly operating on random inheritable variations for long periods of time––has led to this relationship. Chance governs the evolutionary process at its most fundamental level. Because of this, it is expected that repeated evolutionary events will result in dramatically different outcomes. The concept of Historical Contingency embodies this idea and is the theme of Stephen J. Gould’s Wonderful Life:
“…No finale can be specified at the start, none would ever occur a second time in the same way, because any pathway proceeds through thousands of improbable stages. Alter any early event, ever so slightly, and without apparent importance at the time, and evolution cascades into a radically different channel.”1
Gould’s metaphor of “replaying life’s tape” asserts that if one were to push the rewind button, erase life’s history, and let the tape run again, the results would be completely different.2 The very essence of the evolutionary process renders evolutionary outcomes as nonreproducible (or nonrepeatable). Therefore, “repeatable” evolution is inconsistent with the mechanism available to bring about biological change.
A Test for Evolution, A Test for Creation
The idea of Historical Contingency suggests that one powerful way to discriminate between the “appearance of design” that results from the evolutionary process and Intelligent Design is to determine if contingency is operating in the biological realm.3 If life is exclusively the result of evolutionary processes, then biologists should expect to see few, if any, cases in which evolution has “repeated” itself. This is simply not the case. During the last six years numerous examples of “repeatable” evolution have come to light as molecular data has been increasingly used in biological systematics. These findings demonstrate that the evolutionary paradigm fails the test of contingency. The discovery of morphologically identical, yet genetically unrelated organisms does, however, offer powerful support for biblical creation. These examples of “repeatable” evolution include anolis lizards, ranid frogs, cichlids, sticklebacks, mangabeys, river dolphins, and Pericallis, an island plant.
Anolis lizard species found on the islands of the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto Rico) are perfectly adapted to fit into six distinctive ecological niches.4 A species that is perfectly suited for a particular ecological niche is termed an ecomorph. Two examples of Anolis lizard ecomorphs found on the Greater Antilles are small lizards with short legs that live on fragile twigs, and large lizards with large toe pads that occupy the crowns of trees. Morphological analysis of the Anolis lizards that populate the Greater Antilles reveals objectively recognizable groups of ecomorphs.5 Based on their morphological features (or close resemblance), members of the same ecomorph grouping from the different islands were found to be more closely related to one another than lizards from the same island.
Given the contingent nature of the evolutionary process, therefore, it would be expected that each ecomorph evolved a single time from an ancestral species. Each ecomorph produced by a single evolutionary sequence of events would have then dispersed among the islands of the Greater Antilles. However, when this model was tested by comparing mitochondrial DNA sequences of the different Anolis species, it was discovered that lizards in the same ecomorph class were not related to one another.6 This study concluded that it would have taken at least 17-19 separate evolutionary pathways to produce all the Anolis ecomorphs, if natural process evolution was the explanatory agent. Commenting on this work, biologists P.H. Harvey and L. Partridge, state, “It seems that as the tape of life has been replayed in separate islands, there has been a remarkable amount of convergent evolution.”7
Ranidfrogs––comprised of over 1000 species––are common throughout the world. These frogs have adapted to a wide range of lifestyles and habitats. Two of the Ranid subfamilies, Rhacophorinae (tree frogs) and Tomopterninal (burrowing frogs) are found both in Madagascar and on the Indian sub-continent of Asia. They are nearly indistinguishable in their morphological, physiological and developmental characteristics and form two groups of ecomorphs.
Frogs, specifically, and amphibians, in general, cannot migrate through salty environments. Therefore, it has long been held, from an evolutionary standpoint, that the tree frogs and burrowing frogs evolved prior to the separation of the Madagascar-Seychelles-Indian tectonic plate from Gondwanaland (the earth’s one land mass prior to tectonic separation). It is believed that this tectonic plate drifted away from Gondwanaland about 130 million years ago, separated to form Madagascar, and finally attached onto Eurasia to form the Indian sub-continent. Some tree and burrowing frogs were passively carried along and became isolated from one another.
Nuclear and mitochondrial DNA analyses of Madagascar and Indian Ranid frogs demonstrate, however, that the evolutionary explanation is untenable.8 DNA sequence analysis clusters these ecomorphs based on geography not morphological features. In other words, from an evolutionary perspective, burrowing frogs and tree frogs in Madagascar and India must have evolved independently. This same study has also identified examples of “repeated” evolution for Ranid ecomorphs located in Sri Lanka and India.9 Even more amazing, researchers conclude from the DNA sequence analysis that the larval characteristics of several Madagascar and Indian ecomorphs are also identical. This means that the complex developmental pathways and larval lifestyles must have evolved independently on several occasions to produce the same result––if the data is viewed from an evolutionary perspective.10
Cichlids––freshwater fish that are widely diverse in form, color and habits––are scattered throughout the Southern Hemisphere.11 Numerous examples of cichlid ecomorphs have been recognized in lakes Victoria, Malawi and Tanganyika of East Africa. An evolutionary explanation would postulate that each of the ecomorphs evolved a single time and then was independently isolated in each lake after water levels subsided, causing a single lake to split into three geographically separated lakes.12
Sequence analysis of mitochondrial DNA, however, indicates that the ecomorphs found in the three East African lakes must have evolved independently, multiple times, assuming an evolutionary explanation.13-15, 16-17 Also, researchers have noted the independent emergence of ecomorphs for cichlids in two lakes in Cameroon.18 Even more striking is the recent recognition that multiple independent origins occurred for ecomorphs within different regions of a single lake, Tanganyika.19 That is, from an evolutionary perspective, some cichlid species in Lake Tanganyika are viewed as separate, morphologically indistinguishable species that “evolved” in exactly the same way multiple times.
Like the cichlids, scientists believe the sticklebacks species found in British Columbia evolved several times independently to produce the same ecomorphs. The same two stickleback species, bulky benthic (bottom-dwelling) feeders and streamline open-water feeders, live in isolated lakes near the Pacific coast of British Columbia. The standard evolutionary explanation maintains that these two species evolved from one marine stickleback species, became trapped and isolated in the lakes after sea levels changed, and then independently populated the lakes.20 Mitochondrial DNA analysis provides results contrary to the most plausible evolutionary explanations.21 These results indicate that the stickleback species from the same lake have a greater degree of genetic similarity than do morphologically identical species from different lakes. From an evolutionary viewpoint, therefore, stickleback ecomorphs in the isolated lakes must be the product of “reproducible” evolutionary events.
A recent breeding experiment affirms the previous conclusion.22 In a laboratory environment, researchers discovered that corresponding ecomorphs from different lakes attempt to interbreed with one another, while eschewing the different ecomorphs that share their lakes. This result is interesting in light of the biological definition of a species. Biologically, a species is considered to be an interbreeding population of individuals. The willingness of the same ecomorphs from different lakes to interbreed points to just how profound the similarity is among the stickleback ecomorphs––both morphologically and behaviorally.
Mangabeys are large Old World monkeys found in Africa. Morphological similarity has traditionally led biologists to place all the mangabey species into a single genus, Cercocebus. Baboons, drills, mandrills, and geladas are closely related to mangabeys. Earlier molecular studies and mitochondrial DNA sequence analysis challenged the morphologically based classification that places mangabeys into a single group.23- 24 These studies indicated that the single mangabey genus should have been separated into two groups, and that the nearly identical mangabey morphologies must have evolved independently two times. Recent nuclear DNA analyses have confirmed that mangabey morphology “evolved” on two separate occasions, when viewed from the evolutionary paradigm.25
These results not only support two morphologically indistinguishable genera, Cercocebus and Lophocebus, but also indicate that the strong morphological similarities of drills, mandrills and baboons must have evolved independently as well. Nuclear DNA sequence analysis aligns drills and mandrills with the mangabey genus, Cercocebus, and baboons and geladas with the mangabey genus, Lophocebus.26 Inspired by the results of the molecular studies, two biologists have recently recognized subtle morphological differences in dental features and in the arm and leg bones of the Cercocebus and Lophocebus mangabeys.27 However, these skeletal and dental differences are so slight that without the supporting DNA sequence data it is questionable if these differences would have been recognized at all, let alone accepted as significant.
Unlike other marine mammals (whales, porpoises, and dolphins), river dolphins live in freshwater, river environments. There are four extant river dolphin species. Three of these species live exclusively in freshwater and one (the La Plata dolphin) lives both in estuaries and coastal waters. The freshwater dolphins inhabit the Ganges and Brahmaptura Rivers of India, the Yangtze River of China, and the Amazon River.
River dolphins share similar and characteristic morphologies. The most commonplace view among biologists is that the river dolphins emerged from a single evolutionary pathway. Mitochondrial and nuclear DNA sequence analysis now demonstrates otherwise.28 In other words, if the DNA sequence data is interpreted within an evolutionary context, the four river dolphin species must have evolved the same characteristic features independently and repeatedly.
Pericallis, a genus of plants related to sunflowers, are found in the Macaronesian archipelago (Azores, Canary Islands, Cape Verde, Madeira and Selvagens) off the west coast of Africa.29 Of the Pericallis species found in the Macaronesian islands, six are woody and nine are herbaceous. This is not surprising, since many island plants are woody variants of mainland herbs or soft-bodied plants.
The most reasonable evolutionary explanation for the origin of Pericallis woodiness is that it evolved on the mainland and found its way to the Macaronesian islands. However, nuclear DNA sequence analysis betrays this explanation by revealing no genetic similarity. When examined employing evolutionary assumptions, therefore, the data indicates that Pericallis woodiness musthave evolved on at least two separate occasions.30
Evolutionary Attempts to Account for Repeatable Evolution
In isolation, each case of “repeatable” evolution can be viewed as an oddity and poses no real threat to the “truth” of biological evolution. However, the many cases of “repeatable” evolution––in which entire organisms seem to evolve independently and reproducibly––simply doesn’t follow, given the nature of the mechanism available to drive the evolutionary process, chance. Biologists who embrace methodological naturalism––the notion that only natural explanations can be used to account for phenomena in the physical and material world––do indeed regard the occurrences of “repeatable” evolution as unexpected and remarkable. However, their philosophical predisposition does not allow them to be open to the possibility that a Creator is responsible for the repeated occurrences of ecomorphs found in nature. These morphologically indistinguishable, yet genetically distinct ecomorphs can be properly considered as one of the many fingerprints that the Creator has left on His creation. In fact, if a single Creator was responsible for life, one could anticipate seeing repeated examples of the same blueprint throughout the biological realm. One would expect that a single Creator would reuse successful designs over and over again.
Given the examples cited previously, evolutionary biologists cannot seem to account for “repeatable” evolution. One attempt at explaining this phenomenon is to attribute “special” capability to the forces of natural selection.31 Since organisms are perfectly suited for their ecological milieu, and therefore more likely to survive to reproductive age, it is thought that the forces of natural selection––competitive, predatory, and environmental influences––repeatedly “channel” the evolutionary process down the same pathway to produce the same organisms. This explanation for recurrent evolution neglects the fact that selective forces are nothing more than a blind filter. Natural selection can only operate on traits made available by random changes in the population’s genetic makeup. It is not likely that these changes would be repeatable, given the complexity of genomes, nor that they would occur in the same historical sequence.
Additionally, it is unlikely that the factors that made up an organism’s ecology would be identical throughout time. Changes to the ecological environment in Madagascar, for example, would not be identical to the changes in the ecological environment in India. The components of natural selection are influenced by chance and by history. Therefore, natural selection would not be expected to guide separate evolutionary sequences and then produce morphological traits in an organism that somehow remarkably converge.
One well-known experiment with bacteria has led evolutionary biologists to conclude that natural selection can direct the convergence of features in the evolutionary process.33 These experiments demonstrated that bacterial populations subjected to identical environments achieved similar fitness (a measure of the ability of an organism to survive) regardless of chance, mutational events, and history. However, the conclusion drawn from these experiments does not support such a directive role for natural selection for two reasons.
First, fitness is different from morphological characteristics. Fitness describes the capability to survive independent of the organism’s features. It is not surprising that natural selection converges on optimal fitness in mathematical modeling or when characterizing the response of bacteria to environmental stress. Yet, it does not follow that convergence to optimal fitness explains the improbable convergence of morphological features. Second, what is true for bacterial communities (single cell organisms that are morphologically nondescript, comprised of large population sizes, and short generation times) is not necessarily true for the advanced multi-cellular organisms that have been shown to display “repeatable” evolution.33 The population and reproductive characteristics of these advanced, complex organisms preclude their capability to evolve.
Another attempt to account for “repeatable” evolution within the evolutionary paradigm is based on inherent biological and developmental constraints.34 The idea is that these constraints only allow certain variations to occur in the evolutionary process. When evolution occurs, then, it can only produce a limited number of ecomorphs, therefore the same ecomorphs result repeatedly. This explanation falls short. Developmental and inherent biological constraints would have no “knowledge” of the environmental, predatory, or competitive pressures facing the organism. Therefore, one would not expect there to be ecomorphs. In the face of this explanation one must ask, “Why do we see organisms that are perfectly suited to their ecological niche?” The universal occurrence of perfect adaptation is inconsistent with any limitations on biological variation.
Prior to the influence of Charles Darwin (Origin of Species was first published in 1859) scientists viewed the nature of the similarities among organisms as due to the variation of a fundamental design or archetype.35 This “blueprint” for life was acknowledged as having come directly from the mind of God. Organisms classified within a particular grouping were viewed as variations of the design provided by the Creator.
When the tide began to shift toward Darwinian evolution, however, biologists came to understand the relationships among organisms as reflecting descent with modification from a common ancestor. The ancestral species that gave rise to a group of related organisms replaced the archetype, and natural selection operating on random biological variation replaced the creative hand of God.
As both evolutionists and creationists seek to account for the features found in the biological realms, different predictions flow consequentially from these explanations. Chance and a historical sequence of events control biological evolution, at its essence. One would expect therefore, few, if any, instances in which the evolutionary process would repeat itself. On the other hand, if a single Creator were responsible for life on earth, one would expect to see recurrent design throughout nature.
The widespread availability of molecular systematics now allows scientists to test these two interpretations of nature. As molecular systematics is used increasingly to characterize the relationship among organisms––both living and extinct––numerous examples of morphologically identical and genetically distinct groups are being uncovered. The widespread occurrence of repeatable evolution cannot be accommodated within the evolutionary paradigm. Any attempt to account for this phenomenon from a naturalistic standpoint violates the very nature of the evolutionary process or has implications that are inconsistent with what biologists observe in nature.
The evolutionary paradigm fails in the face of the discovery of “repeatable” evolution while biblical creation gains support from this phenomenon. What is interpreted as “repeatable” evolution––morphologically indistinct and genetically unique organisms––is what one would expect if a single Creator has generated life throughout Earth’s history. As time goes on, scientists expect to see more examples of “repeatable” evolution. Each new discovery of this phenomenon weakens the evolutionary paradigm and strengthens the case for creation.
- Stephen J. Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York, NY: W.W. Norton & Company, 1989), 51.
- Gould, 48.
- John Cafferky, Evolution’s Hand: Searching for the Creator in Contemporary Science (Toronto, Canada: East End Books, 1997,) 66-69.
- Jonathan B. Losos and Kevin de Querioz, “Darwin’s Lizards,” Natural History, December /January, (1997/1998): 34-37.
- Jonathan B. Losos, et al., “Contingency and Determinism in Replicated Adaptive Radiations of Island Lizards,” Science 279 (1998): 2115-2118.
- Losos, et al., 2115-2118.
- Paul H. Harvey and Linda Partridge, “Different Routes to Similar Ends,” Nature 392 (1998): 552-553.
- Frankly Bossuyt and Michel C. Milinkovitch, “Convergent Adaptive Radiations in Madagascar and Asian Ranid Frogs Reveal Co-Variation Between Larval and Adult Frogs,” Proceedings of the National Academy of Sciences, USA 97 (2000): 6585-6590.
- Bossuyt and Milinkovitch, 6585-6590.
- Bossuyt and Milinkovitch, 6585-6590.
- Melanie L.J. Stiassny and Axel Meyer, “Cichlids of the Rift Lakes,” Scientific American, February (1999): 64-69.
- Erik Verhegen et. al., “Mitochondrial Phylogeography of Rock-Dwelling Cichlid Fishes Reveals Evolutionary Influence of Historical Lake Level Fluctuations of Lake Tanganyika, Africa,” Philosophical Transactions of the Royal Society of London B 351 (1996): 797-805.
- Stiassny and Meyer, 64-69.
- Verheyen et al., 797-805.
- Axel Meyer et. al., “Monophyletic Origin of Lake Victoria Cichlid Fishes Suggested by Mitochondrial DNA Sequences,” Nature 347 (1990): 550-553.
- John C. Arise, “Flocks of African Fishes,” Nature 347 (1990): 512-513.
- Axel Meyer, “Phylogenetic Relationships and Evolutionary Processes in East African Cichlid Fishes,” Trends in Ecology and Evolution 8 (1993): 279-284.
- Ulrich K. Schliewen, et. al., “Sympatric Speciation Suggested by Monophyly of Crater Lake Cichlids,” Nature 368 (1994): 629-632.
- Lukos Ruber et. al., “Replicated Evolution of Trophic Specializations in an Endemic Cichlid Fish Lineage from Lake Tanganyika,” Proceedings of the Natural Academy of Sciences, USA 96 (1999): 10230-10235.
- Elizabeth Pennisi, “Nature Steers a Predictable Course,” Science 287 (2000): 207-208.
- Eric B. Taylor and J.D. McPhail, “Evolutionary History of an Adaptive Radiation in Species Pairs of Threespine Sticklebacks (Gasterosteus): Insights from Mitochondrial DNA,” Biological Journal of the Linnean Society 66 (1999): 271-291.
- Howard D. Randle, et. al., “Natural Selection and Parallel Speciation in Sympatric Sticklebacks,” Science 287 (2000): 306-308.
- John E. Cronin and Vincent M. Sarich, “Molecular Evidence for Dual Origins of Mangabeys Among Old World Monkeys,” Nature 260 (1976): 700-702.
- Todd R. Disotell, et. al., “Mitochondrial DNA Phylogeny of the Old World Monkey Tribe Papionini,” Molecular Biology and Evolution 9 (1992): 1-13.
- Eugene E. Harris and Todd R. Disotell, “Nuclear Gene Trees and the Phylogenetic Relationships of Mangabeys (Primates: Papionini),” Molecular Biology and Evolution 15 (1998): 892-900.
- Harris and Disotell, 892-900.
- John G. Heagle and W. Scott McGraw, “Skeletal and Dental Morphology Supports Diphyletic Origins of Baboons and Mandrills,” Proceedings of the National Academy of Sciences, USA 96 (1999): 1157-1161.
- Insa Cassens et. al., “Independent Adaptation to Riverine Habitats Allowed Survival of Ancient Cetacean Lineages,” Proceedings of the National Academies of Sciences, USA 97 (2000): 11343-11347.
- Kathryn S. Brown, “Why Woodiness?,” Natural History, December/January (1999/2000): 74-77.
- Jose L. Panero, et. al., “Molecular Evidence for Multiple Origins of Woodiness and a New World Biogeographic Connection of the Macroneasian Island Endemic Pericallis (Asteraceae: Senecimeae)” Proceedings of the National Academy of Sciences, USA 96 (1999): 13886-13891.
- Losos, et. al., 2115-2118.
- Michael Travisano et. al. “Experimental Test of the Roles of Adaptation, Chance and History in Evolution,” Science 276 (1995): 87-90.
- Hugh Ross, “How Speciation “Rules” Rule Out Darwinism,” Facts for Faith 1, no. 2 (2000): 56-57.
- David B. Wake, “Homoplasy: The Result of Natural Selection, or Evidence of Design Limitations?,” American Naturalist 138 (1991): 543-567.
- Michael Denton, Evolution: A Theory in Crisis (Bethesda, MD: Adler & Adler, 1985,) 93-117.