User talk:Kim Bruning/Creationism and macroevolution

Kim Bruning/Creationism and macroevolution

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Modern creationists often make a distinction between macroevolution—any evolutionary change at or above the level of species—and microevolution (a.k.a. "horizontal variation")—any evolutionary change below the level of a species. They often cite Genesis 1:21,24–25 as evidence that each distinct type of creature is its own kind, and cannot be changed into another kind. (This is known as essentialism, or belief that certain things have an irreducible "essence". Psychologists have demonstrated folk beliefs in essentialism arise quite early in children, and some theorize these beliefs are genetically determined instincts.) For example, a man and a dog represent two different kinds, and so it is impossible to turn a man into a dog or vice versa. On the other hand, a poodle and a Great Dane are two breeds or varieties of the same kind, in this case the common dog Canis domesticus, and it is clearly possible to effect change at the microevolutionary level by interbreeding them.

Distinction between "species" and the Biblical concept of "kind"

With the rise of modern taxonomy, the scientific notion of species became distinct from the Biblical notion of a kind. However, they are often confused or conflated. To a creationist, a kind is an immutable attribute of every creature that propagates to its descendants. The kind of a creature determines not only how the creature looks and acts, but also all of the possibilities for how its offspring look and act. Apparent speciation is merely different ways of expressing the creature's inherent kind, and kinds are capable of enough variation that these expressions can appear somewhat different. For many creationists the idea of macroevolution is a contradiction, because it involves a creature changing outside the limitations imposed by its kind—and the limits imposed by its kind are absolute. Why accept microevolution though? Phillip Johnson answers, "microevolution" has "no important theological or philosophical implications" Darwin on Trial 2nd Ed. (118.)

Even as late as the 1700s, most biologists did not think that species changed radically over time. Speciation was thought to be impossible, and Linnaeus expressed the conventional view when he opined that "there are as many species as the Creator produced forms in the beginning." But since the rise of evolutionary biology, species has become a method of grouping those sharing a common gene pool instead of an inherent attribute. Evolutionary biologists conclude that speciation is a rare event but observable.

That is, the majority of biological scientists hold that evolution is not constrained by the Biblical concept of "kind", and that speciation occurs when formerly interbreeding populations cannot or will not interbreed any longer due to accumulated genetic differences. The scientific paradigm is that that speciation is an ordinary event and that cases of speciation have been clearly documented.

For the majority of biologists, macroevolution is not a particularly meaningful term: evolutionary changes are occurring constantly, and macroevolution is merely the accumulation of enough microevolutionary changes that speciation finally occurs. Creationists have stated, however, that there is a limit to the amount of change a kind can undergo - though no such barrier has been observed or even hypothesized, except by creationists. Evolutionists say that such an imagined limit would almost cetainly spell doom for the species as it would no longer be able to adapt to an ever changing planet.

Early creationists denied the possibility of any change whatsoever. However, most modern creationists accept the observable evidence of microevolution in the light of examples such as Darwin's finches on the Galapagos islands evolving from one original base form into a variety of different forms adapted to the circumstances peculiar to their home islands. Similar examples are found in the fossil record and are commonly encountered in studies of organisms with a high rate of reproduction, particularly bacteria and insects. However, creationists treat these changes as expressions of the possible variations within each kind, and not as change of a kind. Macroevolution is treated with considerably more skepticism, and creationists suggest that if it occurs at all—which some deny—it does not occur for the reasons proposed by evolutionary theory. No amount of small changes, they imply, can ever add up to a big change.

Niles Eldridge, Curator in the Department of Vertebrate Paleontology at the American Museum of Natural History says this on the subject in his book The Triumph of Evolution and the Failure of Creationism, "Modern Creationists readily accept small-scale evolutionary change and the origin of new species from old. That, to my mind, is tantamount to conceding the entire issue, for... there is utter continuity in evolutionary processes from the smallest scales (microevolution) up through the largest scales (macroevolution)" (119).

Creationist explanations for variation: Brown bears and Polar bears

To put the micro/macroevolution discussion in context, consider the case of bears. There are many types of bears, among them the brown bear and the polar bear. These two bears are undisputedly related, and they can even interbreed and produce fertile offspring, though they do so only in captivity. However, there are significant differences between the two. The brown bear, for example, is primarily vegetarian, while the polar bear is primarily carnivorous, and there are consequent differences in the teeth of the two bears. Other differences include the obvious camouflage benefit having a white coat (the individual hairs of which are actually translucent) in the arctic where the ability to sneak up on prey is vital. Yet the polar bear's skin is entirely black allowing that light that reaches it through its translucent coat to provide extra warmth. A subcutaneous layer of fat 4 1/2 inches thick protects the bear from the intense cold and provides buoyancy in the water and it has smaller ears and tail to reduce heat loss. It also sports partial webbing between the toes, oversized front feet that act as paddles, and an elongated neck and narrower head to aid in swimming (it routinely swims up to 60 miles from land which is why it is called Ursus maritimus - "sea bear"). Additionally it also has thick fur on the bottom of its feet and suction cup like papillae and vacuoles that buffer and aid in traction on the ice. Polar bears lose so little heat in the freezing arctic that they do not even show up on UV film. In fact they are so well insulated that they can overheat quickly. The polar bear is thus a good example, say scientists, of an accumulation of lots of microevolutionary changes leading to macroevolution.

The Creation Research Society's David J. Tyler in an unusual admission says, "The Polar Bear, however, provides evidence for more dramatic change", "These morphological changes seem to me to go beyond the small, microevolutionary changes which are widely cited in creationist literature", "At the very least, a study of these members of the Ursus group suggests that creationists need to be more positive about larger-scale adaptations (with the appearance of design) than generally appears to outside observers" [1]

Answers in Genesis, however is of the opinion that "virtually all the necessary [genetic] information was already there in the genetic makeup of the first bears, a population created by God with vast genetic potential for variation" [2]. In other words, the original bear kind must have been created with all the attributes that went into making up all the different species of bear that have ever existed incorporated in their genes, and then later on these delineated into specific species [3]. So the genes that make up a polar bear would be present in the first bear. Any genetic changes that have occurred since the fall of Adam are always "downhill" and due to a "loss" of genetic information. To illustrate this premise think of the original kinds as jam packed with loads of genetic information, like batteries. With time and successive generations these genetic possibilities 'strain-out' leaving descendants with less and less genetic diversity. Eventually they begin, as species, to get weaker, wearing down and out; when this happens extinction is not far behind, "the changes we see not only have nothing to do with uphill evolution.... They reflect the overall winding down of information since Adam’s Fall and the resultant Curse on the world" [4].

Weiland also states, "If, as seems probable from fossil evidence, there were no ice-caps before the Flood, there would have been no polar bears at that time". There were no polar caps creationists surmise because the entire earth was created as a uni-seasonal, tropical environment caused by the presence of a "vapor canopy" in the atmosphere. Therefore it is difficult to imagine why God would incorporate genes into the original bear kind that would allow a bear to adapt to a freezing environment. How to explain the polar bears adaptations then? Weiland says that "it is likely that not all the features for today’s bears would have been coded for directly in the genes of the original bear kind. Mutations, genetic copying mistakes which cause defects, may on rare occasions be helpful, even though they are still defects, corruptions or losses of information. Thus, the polar bear’s partly webbed feet may have come from a mutation which prevented the toes from dividing properly during its embryonic development. This defect would give it an advantage in swimming, which would make it easier to survive as a hunter of seals among ice floes." This however, says the evolutionist, ignores the coincidence of its many other marine and cold adapted features.

Taxonomies and Essentialism

The giant panda, on the other hand, is significantly different from other Ursines. Yet since it has many genetic and morphological similarities to bears it is accepted that they are relatives. This leads to the question, what is a bear? A creationist would say that a bear is any creature that expresses the bear "kind". The polar bear and the brown bear are clearly expressions of the bear kind, so they are both bears that have for some reason adapted to very different environments. The giant panda is less clearly of the bear kind while the red is not [5]. If it were possible for pandas to breed with the other bears, creationists have argued, they would also be expressions of the bear kind. If not, then they would most likely be separate creations that simply happen to look similar. However, say evolutionists, this limits acceptable evidence for evolution only to extant species that can breed, leaving out whole other areas of evidence.

To an evolutionist, the polar and brown bears have many genetic and morphological similarities, and they are capable of interbreeding; consequently they are clearly of the family Ursidae, that is, they are both bears, yet they also demonstrate a clear case of divergence. In contrast the pandas, particularly the red panda is an good example of how difficult it is to classify animals that have diverged significantly, its classification has ping-ponged back and forth for years. Says the University of Michigan Museum of Zoology's Animal Diversity Web "The red panda is taxonomically difficult to classify. It was originally placed in the family Procyonidae because of similarities in teeth, round skull, ringed tail, and other morphological characteristics. It has since been placed in the family Ursidae because of similarities in DNA. However, unlike other members of these two families, Ailurus fulgens has an Asiatic origin and has never migrated to the new world. It has been proposed that the red panda be given its own family, the Ailuridae. (Morris 1965, Glatston 1994, Wilson and Reeder 1993)" [6] [7] [8].

The creationist organization Answers in Genesis is also having a hard time with the pandas. For one thing how to explain the panda's "thumb", a useful device for eating bamboo. If they are descended from an original bear kind, why don't other bears have one? If due to a "downhill" loss of genetic information why is it coincidentally so well suited to grasping bamboo, the pandas primary food source? Says AIG's David Catchpoole, "Though creationists are open to the idea that the giant panda is descended from a more generalized ancestral bear ‘kind’, we can’t be sure. One difficulty with such a concept would be explaining why only the giant panda and its possible relative, the red panda ... have a ‘thumb’. Could it be that other bears have lost the genetic information for the thumb, which was present in the originally created bear ‘kind’?.... My assessment therefore is that giant pandas were originally created as their ‘own kind’, already endowed with their distinctive characteristics that suit them superbly to their specialized mode of life." Since the bear could not have evolved the thumb, they say, and since genetic changes are always downhill the likely answer is that the pandas were separate creations from the bears, "pandas are a unique creation of God" this page states flatly. However for lots of reasons, says Animal Diversity Web, "Today it is widely accepted with little doubt that giant pandas belong to the bear family (Ward and Kynaston, 1995)" [9]

For an illustration of the proposed evolutionary relationship of bears see http://www.giantpandaonline.org/lineage.html .

Other examples of clearly related yet distinct creatures include the turtle and the tortoise, and the hyena and aardwolf.

Fossils and macroevolution

Creationists claim that though many varieties of reptiles and mammals exist, there is no record of an animal capable of bridging the gap between them, and that “gaps in the fossil record” reveal “missing links” between different species which refute the idea of gradual transitions.

Fossil finds are generally restricted only to the extremely small amount of sedimentary rock that is exposed on the surface of the Earth at any one time. The vast majority of actual fossils remain concealed within the rock strata. Scientists contend that new fossils are constantly being found and that we have thousands of fossil examples for many species showing transition states from one form to another. Creationists suggest that this evidence only shows examples of microevolution.

In recent years, the theory of punctuated equilibrium has suggested that there might be unevenness in the rate of evolution. It claims that rapid speciation happens in small populations which are cut off from others of their species, and that evolution in these small groups may occur too quickly for any significant number of fossils to be deposited and survive to the present day. The fossil record would thus show an abrupt transition from one form to another. This view has gained significant support among scientists, but it is still somewhat controversial. Creationists counter that punctuated equilibrium is an attempt to dodge the question of gaps in the fossil record by moving the action of evolution into a timeframe when it is impossible to prove or disprove.

Some supporters of evolution say that creationists often query whether a claimed transitional fossil truly represents a transition. According to these supporters of evolution, when a fossil is found that appears to lie in between two existing fossils, instead of representing a transition between them, a creationist will say that this discovery creates two new gaps that need to be explained. But this effectively demands an unbroken family tree of fossils, and since fossilization of organisms is a rare and exceptional event, not the norm, most scientists consider this an unreasonable standard. As a reasonable standard, scientists point to the fossil record of animals such as the horse, whose fossil record is so complete that it is generally agreed not to have any missing links.

Differences in scale

Most biologists consider the difference between microevolution and macroevolution to be relative. Creationists who reject Darwin's theory of evolution through natural selection argue that the difference is absolute. Creationists have proposed that microevolution always takes the form of destructive genetic mutations, which happen to confer an advantage to individuals in a specific environment. Because macroevolution requires many constructive genetic changes, they argue that microevolution cannot lead to macroevolution. One example of a mutation that conferred a competitive advantage under a specific situation occurred in Streptococcus pneumoniae, some strains of which are resistant to penicillin. This mutation causes the bacteria to expend more resources than the unmutated bacteria—and hence, say creationists, this mutation is destructive, or at best not constructive. In a natural environment, without penicillin, this is correct, and the change is disadvantageous. However, if the bacteria are present in a human host, and if the host receives penicillin, only the mutant bacteria will survive—and this, say evolutionists, is precisely how natural selection is intended to work. Because the bacteria now must survive in an environment with penicillin, those with the mutation are suddenly better adapted to survive than those without.

More specifically, the contention of creationists is that the observed and verified process of microevolution does not lead to increasingly complex species. When the mutations occur, they lead to the elimination of certain traits, decreasing the genetic complexity and diversity of the affected species. Creationists claim proponents of macroevolution accept that increases in genetic complexity are brought about solely through improbable major mutation.

Supporters of evolution respond by saying that the mechanisms of mutation show no preference for complexity. Furthermore, if the mutation were disadvantageous, it would probably die out, leaving diversity unchanged, and if the mutation were neutral, it would coexist with the original form, increasing diversity. Lastly, a series of advantageous simplifying mutations could produce a new species.

Creationists claim that although helpful mutations have been observed, mutations that increase genetic complexity have not. This claim does not, however, appear to be borne out by recent evidence from comparative genomics, since larger-scale genetic rearrangements other than mutation, such as gene duplication and chromosome duplication do lead to increased genetic complexity.

Common descent

Creationists who entirely reject macroevolution also reject common descent, the idea that all life on Earth is descended from a common ancestor. Amongst creationists who do accept the theory of evolution, there is debate over whether to accept or reject the theory of common descent, and in particular, the common descent of mankind and other species. Those who reject common descent argue that although other life on Earth evolved, Adam and Eve were fashioned and given life directly by God, unique in the creation. Evolutionary creationists and many advocates of Intelligent Design accept common descent. Michael Behe is one, stating “I dispute the mechanism of natural selection, not common descent.”

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External Links

Macroevolution FAQ

29+ Evidences for Macroevolution The Scientific Case for Common Descent