Catholic Magazine Takes on the AMNH

GilDodgen over at Dembski's place has a post with excerpts from an article that appeared in Crisis, a Catholic magazine. The article, written by George Sim Johnston (whoever that is), is about the Darwin exhibit now showing at the American Museum of Natural History in New York. In just the short excerpt that Dodgen includes, Johnston manages to get much wrong.

The show tells us that Darwin's theory helps us to "understand" the fossil record. This is odd, because the exhibit's curator, the paleontologist Niles Eldredge, has written extensively about how Darwin's idea of gradual evolution has never been supported by the fossils and certainly doesn't explain them.

Johnston is conflating two entirely different ideas from Darwin - the idea of common descent and the idea of phyletic gradualism. The theory of common descent not only helps us understand the fossil record, it's the only explanation that makes any sense out of the fossil record. Common descent is the notion that all modern life forms are derived from one or a few common ancestors via descent with modification. Phyletic gradualism is a theory about the specific mode of speciation, about the manner, mode and tempo with which new species arise from existing species. The theory of common descent not only helps us understand the fossil record, it's the only explanation that makes any sense out of it at all.

The broad patterns of appearance that we see in the fossil record are clear. For the first 3+ billion years of life on earth, there was nothing but bacteria. Then simple multicellular life begins to appear and it steadily diversifies into a variety of forms of marine invertebrates. Then the first hemichordates and chordates appear, then the first true vertebrate fishes. Fish continue to diversify over a long period of time until the first amphibians begin to appear. Then later, reptiles. Finally, mammals and birds.

And within each of these types of animals, there is a similar pattern. The first amphibians to appear look the most fish-like and over time they diversify into many distinct types of amphibians, progressively less fish-like and more like extent species as they adapt to new environments. The first mammals to appear are the most reptile-like and they gradually diversify and become less reptile-like and more like extent species over time. The first birds to appear are the most dinosaur-like and over time they become less reptilian and more like extent species.

The only explanation that makes coherent sense of those patterns is common descent. Now, Eldredge and Gould's criticism of phyletic gradualism as not being supported by the fossil record is an entirely different question. The fossil record clearly supports common descent, but does it support the particular mode of speciation that they call phyletic gradualism? Well, that depends. Darwin doesn't really commit himself to phyletic gradualism the way Gould and Eldredge initially claimed he did.

To a large extent, the battle between phyletic gradualism and punctuated equilibrium (PG) is a mythical one. Speciation can take any number of forms, but the dominant mode is almost certainly allopatric (meaning that speciation takes place in a small subset of a larger population that has become reproductively isolated from the larger ancestral stock). That has certain implications for the more specific patterns we find in the fossil record and that is where PE was valuable, in applying allopatric speciation and Mayr's work on population genetics to paleontology and inferring from it how that would make the patterns of appearance look.

If Johnston understood these basic concepts in evolutionary theory, he would understand why the AMNH exhibit that Eldredge curates could say that Darwin's ideas help us to understand the fossil record while still criticizing what he perceived (wrongly, I think) to be Darwin's focus on speciation as the wholesale transformation of an entire species into a new species. There is much debate about how prevalent the various modes of speciation are over time, but there is no serious debate on the question of whether the fossil record supports common descent.

Eldredge writes in another book... "Nor is the problem a miserably poor record. The fossil record simply shows that this prediction [the existence of close transitional forms] was wrong."

What is in brackets there appears to be inserted not by Eldredge but by Johnson. Eldredge emphatically does not the existence of transitional forms in the fossil record, he only argues that if most speciation is allopatric, and therefore limited in geographical and temporal extent, transitional fossils should be relatively rare. In fact, being misquoted in this manner is one of the things that most rankled Eldredge's partner, Stephen Jay Gould. He wrote:

I count myself among the evolutionists who argue for a jerky, or episodic, rather than a smoothly gradual, pace of change. In 1972 my colleague Niles Eldredge and I developed the theory of punctuated equilibrium. We argued that two outstanding facts of the fossil record--geologically "sudden" origin of new species and failure to change thereafter (stasis)--reflect the predictions of evolutionary theory, not the imperfections of the fossil record. In most theories, small isolated populations are the source of new species, and the process of speciation takes thousands or tens of thousands of years. This amount of time, so long when measured against our lives, is a geological microsecond. It represents much less than 1 per cent of the average life-span for a fossil invertebrate species--more than ten million years. Large, widespread, and well established species, on the other hand, are not expected to change very much. We believe that the inertia of large populations explains the stasis of most fossil species over millions of years.

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.

So what we have here is a traditional creationist quote mine. The quote from Eldredge is criticizing Darwin's belief that transitional forms should be common and often preserved (a belief that, in fact, they overstated initially - in reality, Darwin spoke extensively of the reasons why most fossils would not be preserved and why transitions would tend to take place in isolated areas with small populations and therefore are less likely to be preserved. See here) , not the existence of transtional forms entirely. In point of fact, there are many transitional forms. Indeed, a new one was recently found, as PZ Myers reports this morning.

Not only does Tiktaalik roseae fill in a gap and provide a perfect transitional form between the more fish-like Panderichthys and the later, more land-adapted Acanthostega and Ichthyostega, but it is the result of the ability of evolutionary theory to make accurate predictions. Paleontologists knew that the transitional form between those two groups must have lived in a river environment and must have lived in the time period between the earlier species and the later ones (the early Late Devonian). And they knew roughly what it must have looked like as well. So they went looking for it where they predicted it would be and that's where they found it.

...the phenomena showcased in Darwin and most textbooks...are of no relevance to the question, "Where do the higher animal groups come from?"

But in fact, it is between the higher animal groups that we find the best transitional forms. The evolution of birds from dinosaurs is well documented and getting better documented by the way. We have an array of transitional forms, all appearing in the right temporal and anatomical sequence. The same is true of the orgins of amphibians splitting off from fish (as just demonstrated above and by an excellent series of fossil species) and the origin of mammals splitting off from reptiles (with the brilliantly preserved therapsid reptiles showing exactly how the ear and jaw of the reptiles was transformed into the ear and jaw of modern mammals).

What is the non-evolutionary explanation for such patterns? Did God decide to make birds but, for the first few birds, make sure they looked just like theropod dinosaurs and then gradually, as he made new ones, make them look less and less like dinosaurs (while killing off most of his previous attempts, mind you)? It just makes no sense.

Natural selection simply eliminates what doesn't work. That's all it can do. But the destruction of the unfit does not explain the origin of the fit. As biologist Hans Driesch pointed out long ago, to say that natural selection "creates" anything is a bit like answering the question, "Why are there leaves on the tree?" with, "Because the gardener didn't prune them away." Or, as Arnold Lunn put it, it's like calling the Nazi air strikes creative because they left standing Westminster Abbey.

This is just a ridiculous statement. Talk about horrible analogies. If the leaves on a tree could vary genetically and reproduce, as whole organisms do, then by "pruning away" less fit variations and keeping more fit ones, natural selection would indeed guide the creation of something new. If the buildings left standing by Nazi air strikes reproduced and turned into new buildings, and there was a reason why certain buildings were selected and allowed to reproduce, then natural selection would indeed guide the development of new types of buildings from old types of buildings. But neither leaves (as opposed to trees) nor buildings can reproduce, nor do they compete for resources. This is just a weak argument from very bad analogies.

We know how new traits can be introduced through many mechanisms; we observe it in the lab and in the wild all the time. We know how natural selection can lead to the differential survival of certain traits and the organisms that carry them; this we also observe in the lab and in the wild all the time. And we have observed the creation of new species with distinctive traits, again both in the lab and in the wild.

There has always been an informed minority of skeptics about Darwin, which makes nonsense of the show's claim that his theory is "unchallenged."

Unfortunately, George Sim Johnston is clearly not an informed skeptic but an uninformed one.