Evolution (Rates of Change, Irreducible Complexity)

contents of this page:

6D. Questions about Evolution
Fossils and Gradualism (neo-Darwinism and Punctuated Equilibrium)
Questions from Supporters (of evolutionary theory)
Questions from Critics (re: Rates of Change, Irreducible Complexity)

plus a bonus:
6F. Questionable Criticisms of Evolution
Thermodynamics and Evolution

For two years, this was Section 6D in my Overview of Origins Questions. In 2002, this page was streamlined and reorganized, and was merged into a separate new page, The Process of Logically Evaluating Evolution and Creation, that is now available in a condensed version. Here is the original long version of 6D, with minor revisions:

6D. Questions about Evolution
In an effort to achieve conceptual clarity, a previous section [6B. The Many Meanings of Creation] examined some ways in which theories of creation agree and disagree with each other and with a generic theory of evolution. The process of clarification continues in this section, with a recognition that there is not a single theory of evolution, but a range of theories. All of these E-theories accept neo-Darwinian fundamentals, such as those outlined in Section 6A, but disagree about important details.

Fossils and Gradualism
Theories of oeC agree with basic fossil-E, but challenge a "total fossil-E" claim that the fossil record provides strong support for Total Macro-E. But in the near future, perhaps the fossils won't provide conclusive support for either oeC or E. Why?
In principle, if a species that was quickly created (by oeCi or oeCm) has a changed body structure, this historical discontinuity in natural process might be observable in the fossil record.
In reality, however, finding strong observational support for an oeC conclusion might be difficult because:
1) Some theories of E, such as punctuated equilibrium E — which proposes that new species usually form relatively quickly (on a geological time scale) in small populations — are consistent with a "geologically sudden" appearance of new species in the fossil record. Therefore, it could be difficult to distinguish between a fossil record produced by natural-appearing punctuated equilibrium evolution and by miraculous-appearing old-earth creation by genetic modification — i.e., creation by extensive modification (by changing, adding, or deleting) of the genetic material for some members (or all members) of an existing species.
2) The fossil record is incomplete due to the rarity of fossilization — which occurs only under special conditions, with most animals and plants simply decaying after they die — so even if "links between radically different species" were produced naturally and gradually, these transitional forms might not be fossilized and observed. This could make it difficult to distinguish between a fossil record produced by gradual evolution and by punctuated equilibrium evolution or old-earth creation by genetic modification.

Therefore, it is difficult to distinguish between an apparent gap (due to fossil data being incomplete) and a real gap (due to an absence of the transitional intermediates proposed by neo-Darwinism). But there seem to be good reasons, based on fossil evidence, to question a theory of "evolutionary gradualism" proposing that most macro-E changes are caused by a gradual accumulation of micro-E changes. These gradualist theories have been challenged by some evolutionists, especially since 1972, beginning with Niles Eldredge and Stephen J. Gould.
According to Gould, "The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology [of those who study fossils]. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils. ... The history of most fossil species includes two features particularly inconsistent with gradualism: 1) Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change is usually limited and directionless. 2) Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and 'fully formed.' " (The Panda's Thumb, 1980, pages 181-182)

In this statement, Gould is not challenging Total Macro-E. He is questioning the plausibility of gradualist theories that claim Total Macro-E is mainly the result of slowly accumulating micro-E changes. Instead, Gould proposes a theory of punctuated equilibrium in which the fossilization of intermediates is expected to be rare because a new species forms quickly in a small population. For example:
Imagine that a small subpopulation becomes isolated from the large main population of a species. If the subpopulation is a small "bottleneck" it probably won't be a statistically representative sample, so its gene pool may differ significantly from the gene pool of the main population. And if it is on the fringe of the area inhabited by the species, it may have a different environment and different selection pressures. Due to these two factors, soon (perhaps in a thousand generations, spanning 5000 years) the subpopulation can undergo changes, including the development of reproductive barriers that prevent interbreeding with the main population, and a new species has formed. If the number of individuals in this new species then increases, stabilizing influences (which operate more effectively in a large population) may minimize further changes.
If the new species survives for 5 million years, most fossilization will occur during the long period of "equilibrium" stasis, not in the 5000 years when "punctuated" change was occurring. The fossil record will show a changed new species that appears suddenly (since transitional fossils probably won't form during the short transition period of 5000 years) but does not continue to change. During the 5 million year lifetime of the species, other suddenly appearing species can "branch off" to produce more evolutionary diversification.
In my example above, the timings (for number of generations, length of transition period, and lifetime of species) are within the range of timings typically proposed by punctuationalists in their evolutionary scenarios. I've chosen these timings for illustrative purposes, to show that 5000 years can be a period of time which is biologically long (1000 generations) but is geologically short (when we consider the long time periods recorded in typical non-catastrophic geological formations), and that compared with the life span of a species (5 million years) the time of rapid change (5000 years) can be short, in this case only .1 % of the species lifetime.

A proposal of "geologically rapid" speciation, as described above, is accepted by all evolutionists and oeCs, and by some yeCs. The remainder of this section outlines some of the questions asked by each group.

Questions from Supporters:
According to a prominent college biology textbook, in the modern evolutionary synthesis,
"The paradigm is distinctly gradualist in its view that large-scale evolutionary changes are the accumulations of many minute changes occurring over vast spans of time. Microevolution, the changes in allele frequencies in populations, is extrapolated to explain most macroevolution.
In the classical version of the modern synthesis, natural selection is the major cause of evolution at all levels. Populations adapt by natural selection, new species arise when isolated populations diverge as different adaptations evolve, and continued divergence due to natural selection differentiates the different taxa. The modern synthesis recognizes, and in fact first described, how genetic drift can cause rapid, nonadaptive evolution. But the major emphases of the synthesis are gradualism and natural selection.
A number of evolutionary biologists dissent from the view that the evolution recorded in the fossil record can be explained by extrapolating the processes of microevolution. The debate is partly about the pace of evolution. Many transitions in the fossil record are punctuated, not gradual. Gradualists argue that... Punctuationalists counter that... The debate is not just about the tempo of evolution, but also about the degree to which microevolution compounded over time is sufficient to explain macroevolution.
Some researchers favor a hierarchical theory, with different mechanisms being most important at different levels of evolution. In this view, natural selection is the key to adaptive evolution of a population but is not usually the most important factor in speciation; it plays even less of a role at the level of macroevolution." (Campbell, 1996, pages 477, 479)

Neo-Darwinian evolutionists discuss a wide variety of controversial questions: Were most large-scale changes (in Total Macro-E) produced by a gradual accumulation of small-scale changes (in micro-E and minor macro-E) or was a major role played by radical changes such as those resulting from mutations in regulatory genes that control embryonic development; what were the relative evolutionary contributions of micro-E and speciation, of adaptive natural selection and random genetic drift and historical contingency (due to nonbiological events like meteor impacts or continental drift); what was the relative importance of competitive selection (caused by differences in rates of survival and reproduction) for individuals, for groups within a species, and for different species; what was the tempo of change in the Cambrian Explosion and what were the major causes of change; and (to analyze the significance of a sudden appearance and subsequent stasis of fossils) in what ways and to what extent is there incompleteness in the fossil record, and how much micro-E occurs in ways (such as changes in physiology and internal organs) that are not observable in the fossil record?

Questions from Critics:
The questions above are debated among evolutionists who accept the basics of neo-Darwinism, who claim to be arguing only about details. But their questions — asking "how much diversity and complexity can be produced, in what ways, and how quickly" — go far beyond minor details, giving us reasons to think critically about essentials. Until we have answers that are more satisfactory, creationists (both oeC and yeC) think there are reasons for an open-minded scientist to question an extrapolation of micro-E into Total Macro-E. Two of these reasons, rates of change and irreducible complexity, are discussed below.

rates of change: We can gain a deeper, more complete understanding of evolution by asking, "To produce the changes we observe, what new types of biochemical systems would be required, with how many proteins that are new or modified, and how much change in DNA? How many mutations and selection (or drift,...) would be required, how long would this take, and how probable is it?" {note: Rates of DNA change are important even in cases where mutations in regulatory genes cause major changes in body structure, because a new biochemical system cannot be produced unless the genes for producing it already exist, so analysis of DNA change is still relevant.}

irreducible complexity: In Darwin's Black Box: The Biochemical Challenge to Evolution (1996), Michael Behe claims that some biochemical systems are irreducibly complex due to interdependencies between parts in the system, and therefore could not have been produced in a step-by-step process of natural selection. To illustrate the principle of irreducible complexity, Behe asks us to think about a common mousetrap with five interacting parts: a base, hammer, spring, catch, and holding bar. Each part is necessary, and there is no function unless all five parts are present. A trap with only four parts has no practical function. It doesn't just catch mice poorly, it doesn't catch them at all.
complexity is not the same as irreducible complexity: To understand the difference between complexity that is and isn't irreducible, I find it useful to imagine a system with 20 enzymes (1, 2, 3,...., 19, 20) that can be assembled one enzyme at a time because at each stage there is a useful function that can be selected for: a 1-2 combination is functionally useful (so it offers an advantage and is selected for), but 1-2-3 is even better (so it is selected for), and then 1-2-3-4, and so on. This process of gradually building complexity, in a step-by-step process guided by natural selection, continues until the whole system, 1-2-3-....-19-20, has naturally evolved. The 20-enzyme system is cumulatively complex but is not irreducibly complex. ** By contrast, a system with 5 enzymes (ABCDE) is much less complex, but is irreducibly complex if every subsystem with 4 enzymes (ABCD, ABCE, ABDE, ACDE, and BCDE) is nonfunctional.
For a nonliving system, the implications are even more challenging, because natural selection — which is the main mechanism of Darwinian evolution — cannot exist until a system can reproduce. For the origin of life, we can think about the minimal complexity that would be required for reproduction and other basic life-functions. Most scientists think this would require hundreds of biomolecular parts, not just the five parts in a simple mousetrap.

In Darwin's Black Box, Behe describes actual biochemical systems, and explains why each system seems to be irreducibly complex. What are the evolutionary implications? Behe says, "An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution." (DBB, page 39) Darwin agrees, "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down." (Origin of Species, 6th edition, 1872)
Does such an organ (or biochemical system) exist? Behe's challenge has stimulated creative thinking by scientists, who have proposed imaginative scenarios for a step-by-step evolutionary production of systems that seem to be irreducibly complex. For example, the ABCDE system (described above) could be produced by "ABC --> ABCF --> ABCFD --> ABCFDE --> ABCDE" or by "ABC --> ABCG --> ABCGD --> ABCED" where enzyme-G has mutated into enzyme E. When we evaluate theoretical scenarios like this one (and others that are being proposed) we must supplement creative thinking with critical thinking. Doing this will let us move beyond the easy question (Is the proposed sequence of events possible in principle?) so we can ask the tough questions (Is it plausible in reality, and did it occur in the actual history of nature?) that are scientifically interesting and justifiable.

When we evaluate theoretical scenarios like this one (and others being proposed) we must supplement creative thinking with critical thinking. Doing this will let us move beyond the easy question (Is the proposed sequence of events possible in principle?) so we can ask the tough questions (Is it plausible in reality, and did it probably occur in the actual history of nature?) that are scientifically justified.
And we should remember that the central question is NOT whether all systems that currently are irreducibly complex (as defined at the ** above) would be impossible to produce by undirected natural process. This claim could be falsified (and I think this already has occurred) by showing that plausible evolutionary scenarios exist for some "systems that currently are IC" so these systems could have evolved. But this is not the proper question to ask. Instead, the small-scale research question is whether a particular irreducibly complex system (the one being investigated) could have evolved. And the large-scale theoretical question is whether there is even one IC system whose natural evolution seems extremely improbable. If such a sytem does exist, it would show that Behe's claim is justified.
Systems that currently are IC vary in the apparent difficulty, as estimated by scientists, of being produced by natural evolution. Behe has made claims for only some of these currently-IC systems, those that he thinks would be especially unlikely to evolve. Behe's critics could severely weaken his claims by showing that one or more of the IC systems he has cited (the rotary flagellum,...) could have evolved by undirected natural process. But if critics try to refute him by showing that other IC systems (those for which he has made no claims) could have evolved, this is much less impressive and it does not refute his claims. And if they explain how systems that are "complex but not irreducibly complex" could have evolved, this is totally irrelevant, which is even less impressive.

Summary
According to oeC, current evolutionary theories are adequate for explaining many observations, but not all. Yes, micro-E can fine-tune populations of organisms that already have functioning systems, thus helping them to compete more effectively and to adapt in changing environments. And macro-E can produce new species that are minor variations of existing species, to generate biodiversity. But could evolution produce the changes we observe in the fossil record, in the time that was available? And does natural evolution have enough "creative power" to produce irreducibly complex systems, and to produce other complex systems in the time available?
Unfortunately for science, proponents of neo-Darwinian evolution usually overestimate its scientific status by ignoring the basic Logical Principles for Evaluating Evolution and Creation.

As explained above, we should not avoid logical criticisms of evolution. But we should avoid illogical criticisms, as explained below:

6F: Questionable Criticisms of Evolution
To avoid illogical criticism of evolution,
We should evaluate only accurately characterized modern theories, not distorted strawmen.
We should not imply that debates between evolutionists automatically discredit their theories. { But some of their criticisms do raise questions about neo-Darwinism. }
We should not claim that evolution violates the Second Law of Thermodynamics, since in each step of neo-Darwinian evolution the actions (mutation and natural selection) are thermodynamically allowed, and so is a long process composed of these steps and actions. There are reasons to question evolution, but The Second Law is not one of these reasons. {details about are in the section below}
We should not imply that atheism is a necessary aspect of evolution, because "if atheism then evolution" is not logically equivalent to "if evolution then atheism."

Thermodynamics and Evolution
Contrary to an unfortunately common criticism, the Second Law of Thermodynamics is not violated by theories of evolution. The Second Law is compatible with mutation and natural selection, which are the major actions in neo-Darwinian theories. The Second Law would also be compatible with a process of Total Macro-E that occurred in a sequence of steps involving mutation followed by selection. Why? Since each action (mutation or selection) in each step of the process is thermodynamically permissible, so is the overall process.
In principle, a Darwinian "one-way ratchet" — with harmful mutations producing no major permanent change in a population, and rare beneficial mutations being preserved by natural selection — could produce "genetic information" and increasingly complex organisms.
In reality, is this plausible? When we ask, "What types of complexity can be produced, in what amounts, and how quickly?", there are reasons (*) to question the plausibility of an extrapolation from micro-E to Total Macro-E. We should focus our attention on these scientifically important questions, instead of wasting time on unwarranted criticism that claims the Second Law as justification.
* As explained earlier in this page the reasons include rates of change (In the time available and with reasonable probability, could natural E produce the changes in DNA that would have been required for Total Macro-E?) and irreducible complexity (Do systems exist that could not have been produced in a process of step-by-step evolution?). { a detailed look at EVOLUTION AND THE SECOND LAW OF THERMODYNAMICS: Why do things happen? }

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