Amazon Review - The Theory of Evolution by Natural Selection may be in trouble, but it will have to do until we get a better one.
Michael Denton, "Evolution: A Theory In Crisis."
I came to this book as a person who has absolutely no problem in accepting Darwin’s theory of evolution by natural selection (“TENS”). After all, TENS is the account taught throughout my academic career, it seems to be universally accepted by most – essentially all – reputable scientists, and, then, there are all those fossils of animals and plants that no longer exist and a fossil record that tells when the animals that we are familiar with began to exist. Obviously there was a world of “then” – deep in the past- and the world of “now” and the two worlds are related in some fashion. Something obviously happened over time, and the best explanation is that the animals and plants that existed “then” became the animals and plants that exist “now.”
I have no problem with that idea whatsoever. But when I start to think about the details of evolution – the mechanics of how evolution occurred - I start having problems. How do mutations create new structures? How does chance give rise to the coordinated new structures required for birds to fly – i.e., the unique structure of the feather and the unique structure of the avian lung – or for whales to live in the water – i.e., morphological changes plus changes in the teats of whale mothers and the throats of whale babies required before whales can be born in the ocean? How do these mutations become a species? Is it a long and gradual process of an entire population – in which case, how does it happen in spite of the preservation of dominant traits and regression to the mean? Or is it “saltational” – big jumps by “lucky” individuals, in which case how do they manage to share their genes if the jump is too big? I would like answers to these questions, but I have noticed that the answers seem to short on details and long on tautology. The standard answer seems to go, “well, obviously, coordinated new structures can arise because that is what obviously happened.” My response is usually, “I am not saying that doesn’t happen, but how does it happen.”
Lather, rinse, repeat.
The Thesis of Denton’s book is that these questions – and many other - are a real problem for TENS and that TENS and the scientists who are deeply invested in TENS do not have any good answer for these questions. The eminence grise behind Denton’s book, who makes an explicit appearance in the final chapter, is Thomas Kuhn’s “The Structure of Scientific Revolutions.” Kuhn’s thesis was that science advances only after the structure of an existing science has been undermined by questions and contradictions that are unanswerable under the assumptions of the prevailing scientific theory – the “paradigm” under which the scientists operate. At that point, the old science is ripe for a revolution, when someone has an insight that shifts the way of looking at the problem, and the older science is swept away by the new (although, as Kuhn says, the new science doesn’t coopt the older scientists so much as it makes the older scientists holding the older paradigm irrelevant - science advances death by death, according to Kuhn, sort of like evolution.)
Denton’s book starts with a long historical look at the history of Darwin’s ideas and TENS' assumption that species would develop throug a long, long, gradualistic change within a population. This is a necessary discussion, but unless one is interested in 19th Century scientists like Darwin, Huxley, Agassiz and Cuvier, it seemed long and dry. Denton then moves on to discuss “typology” and its implications. Typology posits that there are actual “types” of species as opposed to a gradual, continuum of form. Nature in fact, according to Denton, is characterized by discontinuities, and not by continuity. Again, this account seemed to be a necessary if not intrinsically interesting introduction before he got down to his real thesis.
When Denton moved on to his actual task – outlining and explaining the contradictions in the evidence for TENS – the book became something of a page turner. Denton makes the point that the fossil record lacks the transitional species that Darwin predicted would exist. Of course, I’ve heard this argument a thousand times as a kind of straw man argument made by my teachers and by scientists shortly before they shot it down. How can, I have wondered, his argument be made in the light of the fossil evidence of the horse and the archaeopteryx? This is probably the first time that I’ve heard a critic of the fossil record make the argument for himself, and, now that I've heard it, the argument seems like a fair one.
Denton points out that we lack the fossils of the transitions between the new type and the old type. So, with respect to Archeopterix what we have evidence of is a bird. Archeopterix has the feathers and wing structure of a bird. Admittedly, it has teeth and it has claws on the end of its wings, but those forelimb structures are wings, and the feathers are feathers with the complex interlocking barbules that stiffen the feather for fight. Where are the feathers with “half barbules” or “three quarter barbules”? Undiscovered, as yet. And, similarly, the archaeopteryx wing is a wing, not a half or three quarter wing. Where is the fossil evidence of the animal that was just slightly in to the process of sacrificing the use of its forelimbs in favor of a new form of propulsion? Who knows?
Denton points out that this is typical of the fossil record. We don’t find the transitional creatures that are supposed to be there for the transition between types. What we do find is fossils that show the type fully developed. This is true of even the living fossils held up as transitional creatures between Linnaean classes, such as the duck-billed platypus and the lungfish. Both are held up as being transitional animals – between reptiles and mammals in the case of the platypus and between fish and amphibians in the case of the lungfish. And yet, according to Denton, on closer examination, we don’t find transitional creatures, we find a “mosaic” of fully developed traits of the respective classes. (See p. 107 – 108.) Hence, according to Denton the platypus has a reproductive system that is “almost fully reptilian” but, of course, it also has mammalian hair, and the lungfish is likewise a mosaic of fully developed fish and amphibian systems.
According to Denton, this is typical of the fossil record. Denton writes, “all the major classes of organisms known to biology are already highly characteristic of their class when they make their initial appearance in the fossil record” (p. 162), which in the face of the idea of continuous and gradual development seems to be a trick like not unlike Athena springing fully grown from the head of Zeus. At their first appearance, angiosperms – the flowering plants that would remake the world – were already divided into different classes. (p. 163.) Ditto with vertebrates and fish (p. 164), and the amazing proliferation of life preserved in the Burgess shale. (p. 161.) In fact, it may be the case that life itself in the form of the cell had this characteristic of a sudden appearance with the essential elements that it would contain for all time. According to Denton, while the traditional view posited billions of years to happen, the current evidence is that we find the modern cell in existence within a few hundred million years of the Earth “cooling off.” This is even more remarkable in light of the fact that for the cell to exist at least two things had to happen simultaneously: there had to be a cell wall that could contain and protect a “transcription machine” that would regulate the activities of the cell, one activity of which would be the manufacture of the cell wall. Chicken meet egg.
Denton’s book seems to be dated. One reason I was reluctant to read it, and a fact that constantly recurred to my mind while I was reading it, was that the book was written in 1986, the Paleolithic period of our genetic/biological/archeological knowledge of evolutionary history. This seems to be a serious drawback for the book but on further inspection, I’m not sure it is. For example, Denton makes a great deal about the absence of fossils of the intermediate species leading from a land animal to the whale, including an otter precursor, a dugong precursor, etc.
During the 90’s, however, these precursors were discovered, but what do these discoveries do to Denton’s thesis? I’m not sure. One reason I’m not sure is that they seem to confirm Denton’s point about the absence of intermediate fossils with respect to key changes in animals from one type to another. The internet has some clever and superficially convincing videos showing these transitional types.
Here is one. The problem for me, though, in light of Denton’s point about types appearing fully developed is that the video shows that happening in the transition from Kutchicetus to Dorudon. Dorudon appears to be a whale, i.e., a form that lives entirely in the water, unlike the Kutchicetus, which is depicted as a fully developed otter. These two types either give birth on land (in the case of the otter-like Kutchicetus) or in the water (in the case of the dugong-like Dorudon.) But where is the species that is developed for either kind of birth? Who knows? So, while the presentation in the video seems superficially convincing, I still have questions.
Likewise, how do we know that Pakicetus and Ambulocetas were in fact precursors to the modern whale? The answer is that both were found to have a particular bone that is found today only in whales. Mmm…okay …fine…so there is no typology of form, except when it comes to identifying precursor species? How do we know that there weren’t random mutations in completely different orders that gave rise to this kind of bone and then died out?
I’ll agree that such a supposition doesn’t seem likely and perhaps it is ruled out by the “law of parsimony” but it does seem ad hoc to appeal to typology while denying typology.
In addition, it may be the case that the last thirty years have provided confirmatory evidence for Denton’s thesis. For example,
it is not hard to find stories such as this one concerning the discovery of a fossilized “Jurassic beaver” that lived 160 million years ago and which has forced scientists to revise and reconsider the diversity of mammals at a time when they were traditionally viewed as primitive shrew-like creatures running scared from the dinosaurs. In fact, every few years, scientists seem to find new fossils that significantly push back the time at which typological traits developed and, thus, seems to rule out the gradual development thesis. In light of the newly –discovered evidence, Denton’s claim that ““all the major classes of organisms known to biology are already highly characteristic of their class when they make their initial appearance in the fossil record” seems to get stronger as time passes.
Ultimately, though, for me at least, Denton explains why I remain a dissatisfied Darwinist; it’s the only game in town. In his final chapter on Kuhn’s approach to the philosophy of science, Denton points out that you can’t beat something with nothing. Pointing out the problems in a science is only the first step to replacing the science. The next step is coming up with a theory that explains the problems that were paradoxical under the previous paradigm. Denton does not provide that theory as far as I could tell. Undoubtedly, his purpose was to highlight the problems in TENS so as to start a discussion “outside the box” of TENS.
But we don't have that theory yet. What we have is TENS. So, until a better one comes along, I will have to take TENS on faith with respect to the conundrums and paradoxes that Denton points out. It may ultimately be the only game that is ever in town. As Denton suggests in his final chapter, "There is still a possibility that living systems could possess some novel, unknown property or charactristics which might conceivably have played a role in evolution." In light of the evidence of types emerging fully developed, like Athena from the head of Zeus, that may well be the case. Perhaps the unknown property we don't understand is the property that answers to the "final cause, or teleology, as discussed by Etienne Gilson in
"From Aristotle to Darwin & Back Again: A Journey in Final Causality, Species and Evolution" but as Gilson points out that discussion is not "scientific" because science has restricted itself from all considerations of final causes in order that it can do its "scientific thing."
The reader of this revew should understand that the last paragraph was my speculation. Denton does not make any foray into theology or mysticism. He stays firmly planted in the world of science with its limitation to two causes - the material and the efficient - and its mechanistic, naturalistic assumptions.
Denton's book is well-written. As far as I could tell from a layman’s perspective, it was fair and accurately recounted the evidence available at the time. It should be read by anyone with an interest in evolutionary theory.