Evolution: The Triumph of an Idea, by Carl Zimmer
HarperCollins, NY, 2001.
A good way to learn science is to study the history behind the science. Quantum mechanics doesnt make much sense until one understands the experiments and ideas leading up to it. Likewise, understanding the cultural and historical context of evolution helps one to understand Darwins theory itself. Carl Zimmer is keenly aware of this. In his wonderfully written and illustrated Evolution: The Triumph of an Idea, Zimmer describes the world of the scientists who developed the theory in a way that helps the reader understand the science itself.
In the tradition of Maitland Edeys and Donald Johansons Blueprints: Solving the Mystery of Evolution and the venerable Time-Life science volumes (where Edey served for many years) Zimmers work is at the high end of the popular science literature. Blueprints had more detail than a typical Time-Life volume but it lacked the vivid illustrations. Zimmers Evolution, the companion book to the generously funded PBS series of the same name, has both. And Zimmer has found a way to write a long book on science that doesnt lose the readers interest.
An important drawback of this genre, however, is its tendency toward the superficial. The unavoidable details that complicate science are often ignored so as not to confuse the message. Pedagogy is sometimes placed above veracity. This same criticism holds for the PBS television series as well, where the viewer was given simplified messages that sometimes misrepresented the state of the theory. It would not be inaccurate, nor I think offensive, to say that the Evolution Project is geared not so much at teaching evolution but at promoting evolution.
As I shall document below, Zimmer consistently tells an overly optimistic story. As a popular tome supporting the pro-evolution perspective, Zimmers work is excellentperhaps the best there is right now. But like the theory it defends, Zimmers work should not be confused with an even-handed, neutral assessment of the facts. As with the television series, the production is excellent but the content is committed to a particular view.
Darwinism is a truly fascinating story within the history of thought, and each time Zimmer oversimplifies he misses another opportunity to tell that story. For example, in formulating his theory, Darwin grappled with the problem of how the blind action of evolution could ever create anything so complicated as life. He took as his example the eye which Darwin admitted made his theory appear to be absurd in the highest possible degree. Darwin then supplied two arguments against such a conclusion. What is interesting about the whole passage is that both arguments are blatantly nonscientific.
The first argument is an old debating trick that requires the opponent to prove the impossible. If it could be demonstrated, wrote Darwin, that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case. Here Darwin called for a universal negative to be provedhardly a scientific criterion.
Darwins second argument against the problem of complexity was even more nonscientific. He admitted that the eye, like the telescope, appeared to be designed, but he warned against this conclusion, for we should not assume that the Creator works by intellectual powers like those of man. Darwin was appealing to certain ideas about God that have traditionally been popular. The argument depends on ones religious beliefs and cannot be judged by science.
Zimmer misses a great opportunity to reveal the subtleties of evolution when he discusses Darwins handling of the problem of complexity. Zimmer ignores these arguments and instead presents a few of Darwins hypothetical scenarios, such as how bats might have evolved from squirrels. It is nothing more than speculation, but Zimmer leaves the reader with the impression that this difficult problem has been practically resolved. [p. 49]
Unfortunately Zimmer misses many such opportunities. There is the immune system and how it illustrates conditions under which natural selection can work. A challenge for Darwinism is that the design space of life is enormous. How is one species to evolve into the next when there are so many dead ends in the way? Random biological variation provides a sampling of the design space from which evolution is supposed to select, but each sample requires a life span of time. In other words, each individual in a population is an evolutionary experiment, but the experiment can take a long time. Furthermore, most of these experiments are not very meaningful, as most individuals have a complement of genes that does not stray very far in the design space.
The immune system, on the other hand, explores a smaller design space using far more efficient sampling. Experiments are carried out rapidly and they tend to be more evenly spread out in the design space. The immune system makes for an interesting analogy with Darwinism. Clearly, it illustrates how natural selection can work, but the process is very different from Darwins proposed process. Zimmer leaves out these complicating issues and instead gives the impression that the immune system serves as evidence for evolution. [p. 92 ff]
In a similar fashion Zimmer enlists evolutionary computing as further justification for Darwinism. Evolutionary computing is a fascinating field that has high potential in a variety of applications. But it requires tremendous effort from computer scientists as they build the controlled conditions that produce meaningful results. It is especially weak as evidence for Darwinism because biologys real-world problems are easily (and necessarily) omitted in the antiseptic world of computer simulation. Furthermore, the results never come easily but require the determined work of computer scientists who carefully design their experiments to achieve the desired results.
Zimmer skips these complicating details. In one of his examples, a scientist used evolutionary computing to design an electronic circuit. Zimmer incorrectly concludes that the good result came without any direction from the scientist. Without the scientists careful design, the simulation would never have produced the good result. [p. 96]
Zimmer states that scientists have found compelling evidence that life could have evolved into a DNA-based microbe in a series of steps. This is overly optimistic to the point of misrepresenting the state of the research. Origin of life research is nowhere near to such an achievement. In fact Zimmers description of the research is liberally sprinkled with qualifiers such as might have, may have, and scientists suspect.
Origin of life research is an area of research that is highly speculative and lacks strong motivating evidence. For many, it seems clear that the research is motivated by the assumption that evolution is true and that the results must be interpreted as such. In other words, researchers will never conclude against a natural origin of life and results will always be given a pro-evolution spin. This is an interesting story that forces one to think hard about the limits of science, but none of this comes through in Zimmers simplified account.
Zimmer writes that the raw materials required for the origin of life could have come from space. Meteorites, comets, and interplanetary dust, he explains, could have seeded the planet with components for crucial parts of the cell. But only a few of the many chemicals used in the cell would have been available and only in low concentrations. For this problem, Zimmer explains that the chemicals might have been concentrated in raindrops or the spray of ocean waves.
If we doubt this particular scenario, Zimmer explains that other scientists suspect that life began at the midocean ridges. And yet another take on the problem is the possibility of cycles of chemical reactions that scientists suspect could sustain themselves. There may have been many separate chemical cycles at work on the early Earth The most efficient cycle would have outstripped the less efficient ones. Before biological evolution, Zimmer easily concludes, there was chemical evolution.
Anyone who has read this literature knows how extremely hypothetical it is and how far researchers are from producing anything resembling the cell. None of this remotely supports Zimmers lofty claim that scientists have found compelling evidence that life could have evolved into a DNA-based microbe in a series of steps. [pp. 104 ff.]
Zimmer discusses evolutions tree of life and its proposed universal common ancestor. In the early days of microbiology all cells were categorized into one of two groups. There were the larger, more complicated cells called eukaryotes and the smaller, simpler ones called prokaryotes. It seemed obvious to evolutionists that the prokaryotes arose first in the history of life and that the eukaryotes appeared later as evolutionary descendents of the prokaryotes.
But in the 1970s researchers first began comparing the genetic material of prokaryotes and eukaryotes in detail. They made two interesting discoveries: first, that there appeared to be a third cell type, and second, that the three types (called eukaryotes, bacteria and archaea) were too different to have evolved from each other. In other words, though the cell types were similar in many ways, no direct evolutionary relationships could exist between them.
Did life arise three times to produce the three similar cell types? Evolutionists said No. They postulated that the three lineages must have evolved from a single progenitor. Having a single progenitor evolve in three different directions would explain the substantial similarities of the cell types without requiring any direct evolutionary relationship between them.
The problem with this explanation is that no fossil or living examples of a potential progenitor have been found. The postulate that it existed and evolved to produce the three different lineages is speculative and is mainly supported by the assumption that evolution is true.
The next step was to piece together what the progenitor would have looked like by comparing the genetic differences and similarities of the three cell types. But the task became confusing when it was discovered that the genes of the cell types varied widely. No clear picture of a simple progenitor emerged; instead, the only solution seemed to be a super progenitor that already had most of the highly complex traits found in each of the three types.
The super progenitor would have been as complex as modern cells yet somehow would have arisen in a short time. Again, evolutionists have proposed a speculative scheme to solve the problem. Perhaps the distribution of genes in the three cell types could have resulted if the progenitor was so rudimentary that genetic material was readily exchanged between cells in the same population. The process is roughly akin to what is known as lateral gene transfer in modern cells but on a grander scale. The result would be that evolution would occur more between neighbors than between parents and offspring.
But this scheme is even more speculative than the preceding one. Not only is there no evidence for such an evolutionary process, but there is a wealth of missing detail. Zimmers version of the story omits these difficulties. He tells the story with plenty of details and he admits that questions remain, but his message, that yet another area of research confirms evolution, is simply not justified. [pp. 103 ff.]
Small-scale evolution, such as insects gaining resistance to pesticides, is hard evidence. Evolutionists use it as one of the major pillars of evidence supporting Darwinism. They often go so far as to say that it demonstrates that their theory is a fact. But there are several problems with this evidence that are consistently ignored. There is the unresolved question of whether small-scale evolution can extrapolate to the sorts of large-scale evolution Darwinism requires. Evolutionists assume that small-scale evolution is unbounded, but there is no scientific evidence for this.
Then there is the existence problem. Evolution relies on the preexistence of biological variation without understanding from where it came. Small-scale evolution is a result of a reproduction process that includes exquisite and complicated molecular machinations. Evolutions explanation for how it created this process is speculative, yet it relies on this process. We are to believe that evolution created the very process that enables further evolution.
These are interesting questions, but Zimmer skips them. Instead, he discusses examples of species undergoing minor variation that tell us very little about the extrapolation and existence problems. For example, Zimmer explains that climate variations on the Galapagos Islands have caused variations in the beaks of finches. After a series of climate variations researchers found no overall trend in the beak size. Though such short-term climate fluctuations have no overall effect, Zimmer tells the reader that significant evolutionary change would be possible given different conditions. But there is no evidence for Zimmers claim, aside from the assumption that evolution is true. [p. 87-8]
Somehow evolution must create big changes as well as small changes. For the big changes, Zimmer explains how easily genes can be duplicated and subsequently mutated to take on new function. [p. 111] However when explaining the advantages of sexual reproduction, Zimmer explains how difficult it is for mutations to produce a good gene. [p. 232-3] And when explaining how evolution can result in quirky designs, Zimmer states that evolution can only tinker with what the history of life has already created. [p. 118]
Darwinism is a very flexible theory and it is tempting for evolutionists to shape the idea to fit the needs of the moment. On the one hand, evolution has created the incredible diversity and complexity of life; on the other hand, it is constrained and has only limited creative powers. Evolution can produce large-scale changes in every direction, resulting in a fantastic variety of creatures and optimal designs. But evolution is also constrained, resulting in the quirks of nature. For every occasion Darwinism has an explanation.
Zimmer also justifies the idea of large-scale evolution by claiming that the observed rates of small-scale evolution are greater than the required rates of large-scale evolution. Traits in guppies, such as their growth patterns, were found to change when the guppies were placed in a new environment. The guppies, of course, were still guppies, but Zimmer argues that the rate of change observed is sufficient to account for changes in the fossil record. But there is no justification for assuming that such small-scale changes fall into the same category as large-scale changes. And Zimmer does not mention that there is no evidence for the underlying assumption that small-scale change is unbounded. Instead, he makes the unjustified conclusion that if you accept microevolution, you get macroevolution for free. [p. 325]
Evolutionists have traditionally argued for large-scale evolution by presenting neat, clean evolutionary diagrams, and Zimmer does just that on page 138. The diagram illustrates an evolutionary progression starting with a four-legged carnivore and ending with an ancient whale. In the text Zimmer gives more details about the actual fossil data but, as they say, a picture is worth a thousand words. The diagram conveys a simplified and carefully tailored version of the true fossil data. It draws attention away from the significant problems with the idea of large-scale evolutionary change.
Darwinism maintains that life comes about on its own. If we are to accept this proposition we must believe that the process is, for the most part, not unlikely. Darwinism needs the unguided creation of life to be an ordinary process rather than a succession of miracles. A good motto for evolution would be: Life Happens.
Throughout the book Zimmer advocates this view of evolution. Regarding the creation of eyes, Zimmer writes, Some crustaceans have eyes that consist of little more than a layer of pigment coated by a membrane. Over time, this membrane could separate from the pigment and begin to act like a crude lens. With small alterations, such an eye could turn into the precise telescopes that birds and mammals use. [p. 49]
And this would include the amazing double eyes that fish use to look through air and water simultaneously. As Zimmer explains: Once the vertebrate eye had evolved, complete with lens, jelly, and backward retina, many lineages evolved new versions that work better in their own environment. For example, three different lineages of fishes have each evolved double eyes. Their eyes have two pairs of lenses rather than one; when these fishes float at the waters surface, one pair of eyes gazes up into the air, while the other looks down into the water. The upward-pointing eyes are shaped to focus light as it passes through air, while the other pair is designed to handle the optics of water. [p. 131]
There are many other amazing eye designs that Zimmer would presumably have no trouble ascribing to the unguided process of evolution. Once you have accepted the notion that the most complicated things we know of arose by the simplest of means, then just about anything can be explained.
Regarding the origin of mitochondria, the powerhouse within cells, Zimmer describes the idea that the ancestral mitochondria was a free-living microbe that merged with a larger cell. It has been suggested, writes Zimmer, that protomitochondria may have hung around early eukaryotes to feed on their wastes, and the eukaryoteswhich could not use oxygen for their metabolismcame to rely in turn on the wastes of the oxygen-breathing protomitochondria. Eventually the two species and the exchanges between them began to take place within a single cell. [p. 114]
There is a quality of credulity in these accounts that makes them difficult to take seriously. It seems that evolution can achieve just about anything we can imagine. Regarding the Cambrian explosion, where so many new species rapidly appeared, Zimmer explains that Because animals already had their complex genetic circuits in place, they could respond to this evolutionary pressure by flowering into all the forms of the Cambrian Explosion Once algae eaters began to thrive, they spurred the appearance of large, fast-swimming predators, which in turn could have been devoured by large predators still. [p. 127]
Likewise, Zimmer explains how blood clotting molecules came about. Imagine an early vertebrate that lacked any clotting factor whatsoever Now imagine that the gene for a slicing enzyme was duplicated. The extra copy evolved into a simple clotting factor made only in the bloodstream. It would be activated in a wound and slice apart proteins in the blood, some of which would turn out to be sticky. A clot would form, one that was superior to the old kind. If this initial clotting factor was duplicated, the chain reaction would double in length and become more sensitive. Add another factor, and it gets more sensitive still. Gradually the entire clotting process could have evolved this way. [p. 329]
Zimmer makes it appear all so easy. But these purported explanations of major evolutionary leaps lack the detail necessary to make them convincing. In reading through Zimmers accounts, the uncommitted reader is driven to suspect that something more than scientific reasoning is at work. The speculation is so rampant and contrary to the scientific method that one cannot help but think that there are deep motives behind evolution.
One of the favored evidences for evolution these days is the universal genetic code, or DNA code for short. The DNA code is used to read the information stored in the cells genetic library, and essentially the same code is found in all species, from whales to oak trees to the bald eagle. Discovered in the second half of the twentieth century, evolutionists triumphantly hail the DNA code as a great confirmation of Darwins theory.
But we may ask: Why does the DNA code confirm Darwinism? The code and its attendant molecular machinery reveal a profound level of complexity about which Darwinism can only speculate. How could such a complex system have evolved? A great variety of explanations of the codes supposed evolution are currently under consideration. And they are filled with more speculation than hard fact. Furthermore, evolution never predicted a universal code. In fact, some evolutionists have expressed surprise that there arent multiple codes in nature. Why arent different codes found among the species? Darwinism would have no problem with such a finding. In fact variations in the code have been discovered and they have not caused so much as a ripple in the evolution camp.
The DNA code is not predicted nor required by evolution, nor can evolution explain how it evolved with any level of detail or certainty. It would seem that this hardly makes for good evidence. The reason evolutionists tout the DNA code as evidence, however, has nothing to do with these issues. Darwinists see the DNA code as evidence that all species are related under common ancestry, regardless of how it evolved.
Of course, no one can deny that the DNA code reveals a relationship between the species. It would be absurd to think it coincidentally arose in all those different species. But there is a difference between relationship and common ancestry. The key to understanding evolution is to understand the metaphysics inherent in this and the other major pieces of evidence for evolution. When evolutionists see a relationship, they explain it using common ancestry regardless of the scientific evidence. The common ancestry explanation is taken as compelling even in the most unlikely cases.
I discuss the source and rationale for this sort of thinking in Darwins God. For now, suffice it to say that, in a subtle way, evolution relies on a particular metaphysical view of nature, and there are examples aplenty of this in Zimmers work.
In trying to rationalize the Cambrian explosion, Zimmer discusses genes that control the development of the nervous system in a wide range of organisms, including vertebrates and arthropods. The genes across this wide range of species are very similar. In fact, a gene from a fly can be inserted into a frog embryo and it will successfully do its job. Such similar genes, Zimmer writes, doing such similar jobs must have a common ancestry. [emphasis added] Zimmer gives no scientific rationale for his striking conclusion, for there is none. The claim that similar genes must share a common ancestry is simply not within the bounds of science. [p. 124]
The PBS Evolution series discusses another such gene-transplant experiment and arrives at the same strong conclusion. Theres only one inescapable conclusion, pronounces geneticist Sean Carroll, which is: If all of these branches have these genes, then you have to go to the base of that, which is the last common ancestor of all animals, and you deduce it must have had these genes. But this is simply not true. Carrolls claim that his interpretation is the only possible interpretation reveals the underlying presupposition that similarity mandates common ancestry.
When discussing evolutions tree of life, Zimmer writes: All living things share certain things in common. All of them, for example, carry their genetic information as DNA and use RNA to turn them into proteins. The simplest explanation for these universal properties is that all living species inherited them from a common ancestor. How could this possibly be the simplest explanation with, for example, the problems of complexity and large-scale change discussed above? This explanation brings with it a multitude of scientific difficulties, but it appears simple if you already believe that similarity implies common ancestry. [p. 103]
When the DNA code and its associated molecular machinery were first discovered it was thought that there was a one-to-one correspondence between genes and gene products. A single gene, it was assumed, produced a single protein or RNA molecule. This was a reasonable first guess, but in later years it was discovered that a single gene could produce multiple products. Overlapping and chimeric genes can produce different products when read in different ways. As a simple example, the word evolution can also be used to spell out the word love if only the first four letters are read, and in the reverse direction.
As if the genetic code and associated molecular machinery were not complicated enough, this additional level of complexity is yet another challenge for Darwinism. We must not only believe that random variations are the source of the meaningful information encoded on the DNA strand, but that those variations also produced overlapping or chimeric genes and the capability to read them.
One interesting example of a chimeric gene involves an antifreeze glycoprotein (AFGP). Antifreeze glycoproteins have been discovered in a variety of Arctic and Antarctic fish. They bind to ice and thus keep the fish from freezing. In the evolution lore this is an example of convergent evolution because the antifreeze genes in Arctic and Antarctic fish must have evolved independently. In this case common ancestry is impossible so similarity is interpreted as convergent evolution.
AFGP is similar to another protein, a functionally unrelated protease. Furthermore, the genes for AFGP and the protease have been discovered both separately and together in a chimeric gene. Evolutionists claim that the existence of the chimeric gene proves that AFGP and the protease have a common ancestry.
Zimmer explains this story, omitting the challenges discussed above. He gives a just-so story of how the protease gene was duplicated and edited to produce the chimeric gene and ultimately the AFGP gene. He concludes that the chimeric gene is a remarkable confirmation of common ancestry. The science may be lacking, but again similarity is assumed to confirm common ancestry. [p. 327-8]
The examples so far have been in the area of molecular biology, but metaphysical assumptions are at the foundation of all evolutionary thinking. Zimmer tells of a mammal fossil uncovered in Pakistan. The creature, dubbed Pakicetus, is intermediate between mesonychids and later whales, confirming that Pakicetus was in fact a 50-million-year-old whale. [p. 137]
But this is not the case. Fossils give us an idea of what creatures existed in the past, but they do not tell us how the creatures got there. Fossils may suggest evolutionary relationships, but they do not confirm such relationships. As one recent paleontology text put it, the observed fossil pattern is invariably not compatible with a gradualistic evolutionary process. There is either a problem with the fossil record or with the idea that evolution is gradual. To make the data compatible with the theory undiscovered fossil forms can be proposed, or unknown mechanisms of evolution can be proposed. But neither of these ad hoc hypotheses are known to be true or untrue. [T.S. Kemp, Fossils and Evolution, Oxford University Press, 1999]
Regarding the Cambrian explosion Zimmer writes, paleontologists have found fossils of multicellular animals as old as 575 million years, some of which are clearly relatives of the groups that appeared during the Cambrian explosion 40 million years later. The fossils Zimmer has in mind show similarities, but his unqualified conclusion that they are clearly relatives goes beyond the data. [p. 324]
What is important here is to understand the nature of these claims. In these various examples Zimmer is not just suggesting possible explanations for the data. Nor can we say that he is merely making provisional claims. In this popular work intended for the non expert, Zimmer is making metaphysical claims under the banner of science.
Another important evidence for evolutionists are the examples of confusing design in nature. Darwin had many such examples and he used them to argue that whereas a blind, undirected process such as evolution would be expected to foul up once in awhile, a Creator would never produce less than perfect designs. Darwins evolution did not explicitly predict such designs, but the theory could accommodate them. The strength of the argument is in its refutation of divine creation. It continues to be an immensely popular argument among evolutionists, and in recent years has been directed against the vertebrate eye. Zimmer approvingly quotes an evolutionists who calls it stupidly designed. [p. 129]
Darwin struggled to explain how his process could produce the complexity of the eye, but now evolutionists have defused the problem. Evolution may not be able to explain how the eye could have evolved in any detailed sense, but evolution seems to be the only alternative. Of course, this argument relies on notions about the Creator and creation that are not open to scientific debate.
When Zimmer writes that similar genes must have a common ancestry, and Carroll says that common ancestry is the inescapable conclusion, they are relying on nonscientific, religious assumptions that are at the heart of evolution. I discuss this at length in Darwins God. The influence of religion in Darwinism is profound but subtle. Unlike Darwins theory which states that many species arise from one, Darwinism is a single idea that arose from many. One cannot simply point to a single motivating metaphysic behind Darwinism. Neither Greek philosophy nor Enlightenment theology nor Deism nor liberalism, for example, can alone explain Darwinism.
Two important influences are Gnosticism and natural theology. Darwinisms debt to these two traditions is obvious, but they are quite different and this makes for a complex story. In any case, what is most important to understand is that the evolution-creation controversy has been misunderstood as science versus religionit is really religion versus religion.
Instead of unwrapping the evolution story and clarifying the myths that have grown up around it, Zimmers work only reinforces those myths. Evolution: The Triumph of an Idea is of high quality volume but it adds little in the way of a fresh understanding to this complex story. In promoting evolution, Zimmer has not captured the essence of this important subject.© 2001 Cornelius Hunter. All rights reserved. International copyright secured. File Date: 11.21.01