A Review of Michael Behe’s The Edge of Evolution: The Search for the Limits of Darwinism

A Review of Michael Behe’s The Edge of Evolution:

The Search for the Limits of Darwinism

By Norman L. Geisler


This book is the follow up of Behe’s revolutionary work, Darwin’s Black Box. Like the first volume, this 307 page tome will also created a stir in the perennial creation-evolution debate. Unlike the first book, the emphasis here is on the limits of evolution rather than the need for intelligent design. Behe’s general conclusions are based largely on the Malaria and HIV studies which enable scientists to determine the rate of “helpful” chance mutations (13) for micro evolution. When this is applied to mutations in living things, Behe believes the mathematical odds eliminate the Darwinian belief that the origin of all living forms can be explained by random mutations and natural selection. This attempt to define the limits of Darwinism provides a way to determine the borders for micro-evolution within an overall intelligent design framework. It is one of the most sophisticated attempts to define the border between macro and micro evolution. The previous effort was by Ray Bolin’s book, The Limits to Biological Change (1984). Much of Behe’s work deals with a technical microbiological discussion of the nature of the cell. However, because of the use of good illustrations, even the scientifically untrained reader can understand the overall argument.

The Central Thesis

Behe concludes that everything from biological classes, types, and phyla clearly need a designer. Everything from species, varieties, and individuals can be explained by purely natural processes like “random mutations, natural selection, and common descent” (1). The Line, then, between, Darwin and design is somewhere in the area of orders, families, and genera (218), though he thinks it is likely that even the orders are designed (193, 199).

In other words, micro evolution (changes within different types) can be accounted for Darwinian processes without any intelligent design. Before that level, however, only an Intelligent Designer can account for the irreducible complexity in living things. Thus, the origin of new life forms cannot be accounted for by a completely Darwinian random processes of chance mutations, and natural selection.

Theistic Evolution

Creationists who missed the fine print in Behe’s first book, acknowledging that he held an overall evolutionary common ancestry thesis, will be disappointed with The Edge of Evolution. For here Behe makes it clear that he is a theistic evolutionist (166, 182, 232). He says: “I’ll show some of the newest evidence from studies of DNA that convinces most scientists, including myself, that one leg of Darwin’s theory–common descent–is correct” (65). He adds, “when two lineages share what appears to be an arbitrary genetic accident, the case for common descent becomes compelling …. This sort of evidence he sees in the genomes of humans and chimpanzees” (70-71). “More compelling evidence for the shared ancestry of humans and other primates comes from …a broken hemoglobin gene” which they share (71). Creationists, however, have shown that a common Creator explains this same data as a result of intelligent design (see Fazele Rana and High Ross, Who Was Adam?, 2005, Chapter 14).

Behe seems to favor the position that “intelligent design is quite compatible with the view that the universe operates by unbroken natural law, with the design of life perhaps packed into its initial set-up” (166). Thus, “the bottom line is this: Common descent is true; yet the explanation of common descent … is in a profound sense trivial” Why? Because “It does not even begin to explain where these commonalities came from, or how humans subsequently acquired remarkable differences” (72). Behe believes that it comes from pre-planned and pre-set intelligent design, perhaps from the moment of the Big Bang.

Random Changes are Inadequate

As one would suspect from his first work, Behe reaffirms his initial thesis that “Random duplicating a single gene, or even the entire genome, does not yield new complex machinery… [or] novel, complex forms of life” (74). Indeed, he insists that the studies since his first book show that “the problems of its [cilium’s] irreducible complexity has been enormously compounded” (94). And “The cilium is no fluke. The cell is full of structures whose complexity is substantially greater than we knew just ten years ago” (95). He also points to the incredible timing it takes to construct a cell, comparing it to the preparation and execution of the material and machinery necessary to erect a large building (96).
Returning to the bacterial flagellum (motor mechanism), he calls it “mind-boggling complexity” (101) since we know there are control switches that exert control over its construction. Citing noble laureate Francis Crick, Behe concludes that “An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going” (216).

Possible Divine Interference

In spite of his common descent thesis, Behe allows for the possibility of divine “interference” after the initial creation at the Big Bang. He concludes: “The bottom line is that, if one allows that a being external to the universe could affect its laws, there is no principled reason to rule out a priori more extensive interaction as well” (210). In short, “If there really does exist an agent who tuned the general laws of nature with the goal of producing intelligent life, then it’s reasonable to think the agent would have taken whatever further steps were necessary to achieve its goal” (213). However, typical of evolutionists, with or without and initial Creator, Behe agrees with the party-line criticism that this positing a series of creative events after the beginning is an unnecessary God-of-the-gaps move.

The Anthropic Connection

Behe skillfully ties his intelligent design thesis in with the anthropic principle (207-208), saying, “It’s reasonable to conclude not only that the universe is designed, but that the design extends well beyond general laws, at least down into particularities of the physical and chemistry of certain molecules” (210). This has the advantage of showing that the designer is beyond the world and that He preplanned emergence of complex life before the Big Bang. He declares that “the hard work of many scientists across many scientific disciplines in the past century unexpectedly demonstrated that both the universe at large and the earth in particular were designed for life. The heavens and earth–and life itself–alike are fine-tuned” (210). In spite of this, Behe strangely allows the view that the Designer may be within the universe like Fred Hoyle proposed (228). However, this is not consistent with the fact that the Designer preplanned the original Big Bang event before the natural world existed and pre-packed it with the necessary conditions for human life to emerge.

The Evidence for Intelligent Design

Behe posits two criteria for an intelligent cause. First, the odds against a natural cause must be great. Random mutations cannot explain the irreducibly complex nature of life for “the majority of even helpful mutations are lost by chance before they get an opportunity to spread in the population” (111). In short, the complex structure of the cell makes it unreasonable for blind Darwinism to navigate the maze necessary for life (113). For both the necessary parts and the action to achieve cell construction make it highly improbable that it would occur naturally (121).

By comparison with the HIV virus in which nothing “significantly new or complex” (155) developed in 1020 copies, Behe concludes that the likelihood of even simple helpful changes for complex cell construction are virtually nil. It is in this connection that Behe offers a helpful distinction between mere theoretical possibility (which Darwinian evolution depends on to make its case) and biologically reasonable expectation (103), namely, something that is likely to occur in nature (which Darwinians is not).

Second, the evidence of purpose is necessary to posit an intelligent cause. Indeed, Behe defines “design” as “the purposeful arrangement of parts” (168). Rational agents can coordinate things into a large system like a ship. Such an arrangement is not only highly unlikely to occur by chance, but we know from previous experience that an intelligent agent can organize things in this manner. All necessary parts must not only fit together but they must stick together (124-126). Even two new useful properties need an intelligent cause since the odds are 1040 against it. This is more than all the mammals that ever lived (135). This is so unlikely that it calls for an intelligent cause at the outer edge of evolution (145-146).

The Role of Chance (220).

The design thesis is not extended by Behe to every detail of the universe. He asks: “Is nothing left to chance? No, there is no reason to think that any but a minuscule fraction of the details of the universe or life are intended” (219). So, “we have no scientific evidence of the design of the details of most inorganic matter” (220). Hence, “Explicit design appears to reach into biology to a certain level, to the level of the vertebrate class, but not necessarily further, Randomness accounts perfectly well for many aspects of life. Contingency is real” (220). In making this claim, Behe is not discounting that even the tiniest cells are elegantly designed. He insists that random mutations can not take many coherent steps by purely natural processes (179).

Addressing Objections
Behe addresses several objections to His view. One deals with the possibility of numerous universes of which this one is the lucky shot that turned up where life emerged, as improbable as it may have been in a single universe.

The Multi-Universe Hypothesis

Behe addresses the atheistic response that this universe is only an isolated oasis of apparent design in a vast dessert of chance involving multi-universes (221) which make this unusual universe in which we live a plausible result of chance. He believes this hypothesis actually undercuts Darwinism for the models are purely speculative and iffy. That is, there is no observational evidence for such an hypothesis–which is the very basis for science. Further, on such a scenario only a bare-bones universe would be produced, not the lush one we have (223). Science can only deal with what is–not with what one imagines or wishes there to be.

Behe struggles with the infinite universes possibility which would explain this one as one of the many that would actualize in that amount of time and space. However, being unarmed with solid philosophical reasoning, he does not seem to realize that one cannot have an actual infinite number of actual universes (but only abstract ones). He does note that an infinite universes hypothesis would undermine both any meaningful sense of evidence and the fact that all false thought will appear endlessly in such a scenario. More fundamentally, he asserts that science is based on the premises that the universe is real and our senses are reliable. Without this even the first steps of reasoning are impossible (226). But granted these, the infinite universe scenario is unfounded.

The Religious Connection

In answer to the objection that the design position leads to God, Behe quotes Nick Bostrom with approval, affirming that “The ‘agent’ doing the designing need not be a theistic God …,” even though that is one possibility (228). He believes–I think wrongly–that “To reach a transcendent God, other nonscientific arguments have to be made–philosophical and theological arguments” (229). Much of the book deals with a technical microbiological discussion of the nature of the cell. However, by the use of good illustrations even scientifically untrained readers can understand the overall argument.

The God of the Gaps Objection

This reasoning, Behe insists, is not “God of the gaps” because non-randomness “encompasses the cellular foundation of life as a whole” (147). In short, it is not the lack of evidence for a natural cause but the presence of an all-permeating presence of purpose that points to a designer. According to Behe, “purposeful designer” is taken in a broad sense (229) to include either a supernatural cause beyond the universe or one inside the universe. For “the designer need not necessarily even be a truly ‘supernatural’ being.” Thus, he argues that “if one wishes to be academically rigorous, he can not leap directly from design to a transcendent God” (228). But this conclusion is unnecessary in view of Behe’s own argument since the anthropic evidence points to a supernatural cause beyond the universe, as does the evidence for the Big Bang to which he alludes. For the cause of the whole natural universe cannot be part of the universe. And the only Cause beyond the natural universe is by definition a supernatural Cause. Indeed, on his own definition of science as a conclusion relying on physical evidence, “plus standard logic” (233) one can logically infer a supernatural cause from the Big Bang origin of the entire natural universe, as we just did.

Common Ancestor or Common Creator

Behe argues that: “If mammals and flies use the same switching genes, it is reasonable to think that they inherited them from the same ancestor or ancestors” (182). Indeed, it is true that “every Hox gene seen in the fruit fly has a very similar counterpart in humans!” (180). However, Behe forgets that from this we need not infer common ancestry. For it is also reasonable to conclude that they have a common Creator. For common design points more reasonably to a common Designer than to a common ancestor. For example, the progressive models of airplanes from the Wright brothers to space ships are not evidence of a common ancestor but a common creator. And in many case a function that worked well in a previous model was incorporated into a later one.

Is the Bible Scientific?

Behe claims that it is “silly” to treat the Bible “as some sort of scientific textbook” (166).
However, while the Bible is not a systematic science text on the various sciences, nonetheless, there is no evidence to demonstrate that it is not scientifically accurate when it speaks on matters of origin. Indeed, modern science has confirmed the basic facts of Genesis one: 1) There was a Creator of the universe (Gen. 1:1). 2) First life was created (Gen. 1:21). 3) The basic kinds of multi-cellular life “exploded” on the scene in the Cambrian (Gen. 1:21-24). 4) All forms of life appeared fully formed from the beginning. 5) These forms of life remain basically the same throughout their geological existence, producing after their kind (Gen. 1:24). 6) Human beings are unique creatures with distinctive intellectual and moral capacities, even God-consciousness (Gen. 1:27). Even the Agnostic astronomer Robert Jastrow concluded, “”Now we see how the astronomical evidence leads to a biblical view of the origin of the world. The details differ, but the essential elements in the astronomical and biblical accounts of genesis are the same: the chain of events leading to man commence suddenly and sharply at a definite moment in time, in a flash of light and energy” (God and the Astronomers, 14).

Does Nature Self-Organize?

Darwinian evolutionist claim that nature performs self-organizing acts such as hurricanes. But, as Behe points out these systems are not like “complex genetic systems” (159). They have no irreducible complexity, nor do they have any specified complexity such as the DNA has. Hence, this Darwinian analogy is fallacious.

Origin vs. Operation Science

Behe shows no evidence that he understands the distinction between origin and operation science distinction that we made in our book, Origin Science (1987). In fact, he seems to blur them in his definition of science as “any conclusion that relies heavily and exclusively on detailed physical evidence, plus standard logic” (233). But this is too broad and does not bring out the distinctives of each domain. Operation science deals with observed regularities in the present, but origin science treats unobserved singularities in the past. The first one is an empirical science which includes micro-evolution, but not macro evolution. It relies on observation (and experimentation) and repetition. Each theory, therefore, must be measured against a recurring pattern in the present.

However, origin science operates like a forensic science. It involves neither repetition nor direct observation of events. Rather, it relies on two other principles: causality and uniformity. The first principle posits that there is a cause for every event. The second principle declares that the kind of causes know by repeated observation in the present to produce certain kinds of events in the present are assumed to be the same kind of causes to produce like events in the past. And the two basic kinds of causes are intelligent and non-intelligent natural causes. Sciences that deal with intelligent causes in the past includes both forensic science and origin science. Had Behe explicitly used this distinction, he could have solved more problems more readily. Likewise, speaking of “testing” (233-234) an origin hypothesis is misleading in the normal sense of an empirical test. In a forensic situation, being a singular unobserved past event, there is no such way to “test” the event. One can only posit a certain kind of cause (known from repetitions in the present) as the most likely cause of that past event of origin, whether a non-intelligent natural cause or an intelligent cause.

Prediction or Retrodiction?

Failing to distinguish origin science form operation science, Behe labors to explain how intelligent design can make predictions better than Darwinian evolution (188-189, 234). But neither theory as such is primarily concerned with making predictions, though some may be inferred from them. Origin science, such as macro evolution and creation, deals with projecting back (retrodiction) from present evidence to past causes based on uniformity (the present is the key to the past). Hence, the main concern is not with verifying the theory by predictions, but with identifying the proper cause for the specific events, whether non-intelligent natural one or an intelligent one.

Suffering and Design

Behe briefly tackles the painful problem of suffering (237f.). He responds to the argument that “because it is horrific, it was not designed” by pointing out that the “revulsion is not a scientific argument.” Indeed, he insists that “denying design simply because it can cause terrible pain is a failure of nerve, a failure to look at the universe fully in the face” (239). Of course, this is a less than satisfying answer to the problem. A more direct response would be to point out two things. First, suffering does not negate the strong evidence for design. At worst, it only raises questions about the nature and purposes of the Designer. Second, the attempts to disprove the Creator based on the apparent lack of purpose for suffering are notoriously unsuccessful. At best they boil down to this: “The Creator cannot have a good purpose for allowing suffering because the creature cannot think of one.” But clearly if the Creator is infinite in knowledge, then we would expect that He would know infinitely more than we do. And if He is absolutely good (which He must be or else we could not know the world is not-perfect without this absolute standard of Perfection by which to measure it), then He must have an absolutely good purpose for everything, even if we do not know it (Deut. 29:29; Rom. 11:33).

Purpose for Apparent Randomness

Behe seems to lack a full understanding of the relation of randomness and design. They are not mutually exclusive. There is a purpose or design for randomness. For example, the random mixing of carbon dioxide which humans exhale has a good purpose, namely, it keeps them from inhaling the same poison because it did not mix with the air we inhale. Likewise, random natural selection has a good purpose: It enables various kinds of animals to survive by adapting to adverse circumstances. In short, it helps the race survive when weaker individuals are eliminated. Just as a saw mill uses the “wasted” saw dust to make other products, even so there is a purpose for the “wasted” animals who did not survive. They provide food and fertilizer for those who do survive.

Likewise, Behe’s argument for common ancestry based on alleged common mutations in genes between primates an humans is fallacious. Just as the once 180 vestigial organs of Darwin’s day have diminished to virtually none, even so, the recently so-called “junk” genes are now known to have a crucial purpose in the development of life. Any alleged “ waste” in God’s universe is probably a byproduct of a good purpose such as higher life living on lower forms. But even this byproduct of a good process (like saw dust from cutting logs) has a good use. Darwin’s view of nature that is “red in tooth and claw” was not the paradise God made in Eden (Gen. 2), nor will it be the Paradise regained in the end (Isa. 65:25; Rev. 21-22). It is the Paradise lost because of man’s sin (Gen. 2:16-17).


In summation, Behe’s work is a mixed blessing to the creation and intelligent design movements. It is a blessing in that: 1) It strengthens the already good argument from specified complexity to an intelligent Designer; 2) It provides a scientific basis for the limits of biological change known as micro-evolution or variation within created kinds or types of life. On the down side: 1) Behe does not seem to understand the difference between operation science and origin science (see my book Creation in the Courts (Crossway, 2007), Chap. 8); 2) He does not see how the scientific evidence leads to a supernatural Cause; 3) He buys into the unfounded argument that similarity shows a common ancestor, rather than a common Creator; 4) He wrongly assumes that some apparent mutations are evidence for common ancestry when they are really highly complex means produced by an intelligent Designer. Thus, so-called “junk” genes are not really junk. Crucial roles have been discovered for them in the increasing complexity of life. And not all apparent mutations are real ones. Granted that it took a supernatural and super intelligent Cause to produce this world (as the Big Bang and Anthropic evidence shows), there is good reason to believe that “God does not make junk!” And if it looks like junk, then scientists need to take another look. For the history of science has shown that apparent left-over organs and junk genes have turned out to have important functions. Any One who can pre-plan and produce a highly complex universe as this one should not be charged with purposeless activity. It is more likely that we are dumb than it is that a supernatural Creator is dead.