From the lesson Plan

From the Creationist Literature

What scientists say.

The fossil record shows an increase in the

complexity of living forms from simple one-celled organisms, to the first simple

plants and animals, to the diverse and complex organisms that live on Earth today.

This is the idea of “directed evolution” promoted by Intelligent Design writers such as Jonathan Wells [see Icons of Evolution, Chapter 10].

The increase in observed complexity is not the basis for common descent, which is what “later forms evolved from early simple forms” means. Among the main bases for the theory of common descent are (1) the distribution of homologous organs and structures (2) the observed biogeographical distribution of species, (3) the many transitional forms observed in the fossil record, and (4) the concordance of phylogenetic trees constructed from morphological and molecular data. The observed change in complexity over geological time has no particular bearing on the theory of common descent.

Simple, unicellular organisms are still the most abundant lifeforms, found in all environments across the globe.

This pattern suggests that later forms evolved from earlier simple forms over long periods of geological time.

As indicated for the previous sentence, the “pattern” does not exist. The fossil record supports macroevolutionary change by showing the morphological and structural similarities of closely-related genuses and species, and their modification through time. A great test of the Theory of Evolution occurred in the 1970s and 1980s when phylogenetic relationships between living organisms were shown to closely match the phylogenetic relationships based on structural similarities.

Macroevolution is the large-scale evolution occurring over geologic time that results in the formation of new taxonomic groups.

Macroevolution and microevolution are not common terms in the scientific literature. However, they receive strong emphasis in the creationist literature where an attempt is made to show that they represent two completely separate biological processes.

“There is also a continuing debate about whether it is necessary to "decouple macroevolution from microevolution." Some experts do not believe that major changes and the appearance of new forms (i.e., macroevolution) can be explained as the products of an accumulation of tiny mutations through natural selection of individual organisms (microevolution). If classical Darwinism isn't the explanation for macroevolution, however, there is only speculation as to what sort of alternative mechanisms might have been responsible. In science, as in other fields, you can't beat something with nothing, and so the Darwinist paradigm remains in place.” [Phillip Johnson, October 1990; http://www.arn.org/docs/johnson/pjdogma1.htm]

Macroevolution, as most commonly employed in evolutionary Biology and Paleontology, includes the development of new species from “parent” populations - which cumulated over time result in new taxonomic groups. Microevolution is simply a subset of macroevolution. Creationists who propose that these are two distinct and separable processes have never been able to define any limits to microevolution.

Exciting recent discoveries related to modifications of the HOX gene show that major modifications in body plan can come about rapidly with very limited genetic change.

The slow transformations are reflected in transitional fossils such as Archaeopteryx (a reptile-like bird) and mammal-like reptiles.

This statement suggests that the “traditional” evolutionary view is of slow change over time; and that a controversy exists in the biological community as given in the challenge sample answer. This is a false dichotomy.

There is no evidence from the fossil record to indicate whether Archeopteryx developed rapidly or slowly from its ancestral populations.

Evolution is not rate dependent. Some evolutionary changes in organisms appear to be the result of gradual changes over time; other change apparently happened rapidly on a geologic time frame.

These transitional fossils bridge the gap from one species to another species and from one branch on the tree of life to another.

This is not the Paleontological definition of transitional fossils.

Paleontologists and evolutionary Biologists prefer to talk about organisms which contain features that are transitional between different groups of ancestor and descendent organisms. The use of the term “transitional fossil” implies knowledge of specific ancestor and descendent species, which is seldom known. Fossils with transitional characteristics show the changes between species along branches of the phylogenetic tree, not between branches.

Transitional fossils are rare in the fossil

record.

This is a commonly expressed viewpoint in the creationist literature and is completely false! For example:

“A severe problem for evolutionists is the absence of transitional forms in the fossil record. By transitional forms, we mean intermediate forms of life appearing in the fossil record that are "in-between" existing types of organisms found today or in the past.” [http://emporium.turnpike.net/C/cs/fossils.htm]

When the correct definition of “transitional” is used (see above), the opposite of the statement is true. Nearly every fossil is transitional between a line of ancestral species and a series of descendent species along a branch of the phylogenetic tree (sometimes one species is seen to have characteristics transitional between 2 or more closely related descendent branches). The spotty nature of fossilization as a process prevents us from observing every minor change between species (except in a few rare but well documented cases); however, the overall pattern of change, and the similarities of the structures involved are commonly very clear.

A growing number of scientists now question that Archaeopteryx and other

transitional fossils really are transitional forms.

This statement is completely false The indefinite term “a growing number of scientists” is a common ploy in tabloid journalism and in creationist literature to erroneously portray disagreement with the current state of affairs.

Here’s an example of creationist language: “The most often cited "example" of a transitional form is the Archaeopteryx which has been touted as a reptile to bird transition. However, this creature is controversial and enveloped in dispute.”

While it is no longer viewed as being in a direct line of ancestry to modern birds, the overwhelming consensus of paleontologists and evolutionary biologists is that Archeopteryx displays physical characteristics transitional between reptiles and early true birds. The current scientific debate is over which reptilian family is ancestral, and also which fossil lineage led to modern birds.

The fossil record as a whole shows

that major evolutionary changes took place suddenly over brief periods of time

followed by longer periods of “stasis” during which no significant change in form or transitional organisms appeared (Punctuated Equilibria).

It is a common creationist tactic to present evolution as a series of “either-or” propositions, making it appear that scientists never agree on any point.

“Darwin insisted that changes had to be small and gradual. However, Gould and his associates (1980) have proposed static intervals (stasis), followed by periods of rapid change (punctuated equilibrium).”

[http://www.arn.org/docs/mills/gm_originoflifeandevolution.htm]

“The debate over PE [punctuated equilibrium] has given publicity to stasis as a serious problem for evolution (how can you believe in evolution, or change, when the fossils testify to stasis, or lack of change?). The recognition of the reality of abrupt appearance and stasis corroborates what creationists have been saying since Darwin -that the evidence fits special creation combined with the results of a worldwide Flood.” [http://www.answersingenesis.org/home/area/magazines/tj/docs/v8n2_punc_equilibrium.asp]

The challenge statement is incorrect. Both gradual evolution and rapid change have been observed in the fossil record. A critical factor in any assessment of “rates of change” is the pattern of fossilization. For instance, ocean dwellers leave many more fossils than terrestrial organisms living in upland areas.

See also the essay Evolution as Fact and Theory by S.J. Gould, one of the originators of this idea.

    “We proposed the theory of punctuated equilibrium largely to provide a different explanation for pervasive trends in the fossil record. Trends, we argued, cannot be attributed to gradual transformation within lineages, but must arise from the different success of certain kinds of species. A trend, we argued, is more like climbing a flight of stairs (punctuated and stasis) than rolling up an inclined plane.

    Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists—whether through design or stupidity, I do not know—as admitting that the fossil record includes no transitional forms. Transitional forms are generally lacking at the species level, but they are abundant between larger groups.”

The “Cambrian explosion” of animal phyla is the best known, but not the only example, of the sudden appearance of new biological forms in the fossil record.

From the creationist literature:

“Life did not start out simple and evolve into more complex and diverse animals; it was complex and diverse right at the beginning. This contradiction between the fossil data and the predictions of evolutionary theory falsifies the theory.”

[http://www.straight-talk.net/evolution/explosion.htm]

“Newer evidence against Darwinism is emerging as well. In paleontology, the Cambrian explosion has long posed problems, revealing that all the major body plans for animals appeared in the fossil record at the same time--a pattern inconsistent with Darwinian gradualism.”

[http://www.arn.org/docs/pearcey/np_ctoday052200.htm]

The rate at which new phyla came into being during the early Cambrian Period is an area of active research. The fossil record for the upper Precambrian and lower Cambrian has been sparse for a number of reasons (most organisms did not have hard shells which are readily fossilized; there is limited exposure of lower Cambrian strata around the world). Regardless, the Cambrian “explosion” occurred over a substantial time period of 15 - 35 million years.

Current investigations in Australia and Canada are showing that there was a wide diversity of organisms living in the late Precambrian, extending the origin of phyla by many millions of years.

Creatures resembling trilobites, fossil imprints of jelly fish, sponge spicules, various types of worms (and worm burrows) are found in Precambrian strata tens to hundreds of millions of years before the lower Cambrian. Cambrian organisms had a long ancestry.