Radio talk show discussion on common descent

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One of the things I am interested in is the common “man in the street” objections to the theory of evolution. A very common concern is the “micro” vs. “macro” distinction: many people can accept evolution within a species, but just can not see how one species can ever evolve into something else. Such people therefore can not accept common descent, which is a central tenet of evolutionary theory.

I’ve recently had two interesting encounters with this: one last week during an appearance on a conservative radio talk show and the other in response to an unsolicited email from a member of Dr. Kent Hovind’s staff. In both cases I was met with considerable resistance to the obvious question of “if common descent isn’t the means by which new species have came into existence, then what is?” The obvious answer - the one which was the default historically before the theory of common descent and the one held by many anti-evolutionists today, is special creation: creation ex nihilo, the immediate materialization into existence of new organisms. However, as the following encounters show, anti-evolutionists are reluctant to put this on the table as an actual “competing hypothesis.”

In order to illustrate, I would like to summarize these two encounters, the first here in this post and the other in a second, separate post.

Thursday, December 30 I was on the Jerry Agar Show, a conservative talk show on radio KMBZ in Kansas City, to talk about evolution. We had agreed that I would try to answer some of Jerry’s questions about evolution, and that the subject would not be intelligent design, religion, or the politics of state science standards - we would focus on Jerry’s concerns about the “holes” in evolutionary theory. I was interested in seeing what ideas Jerry felt were most worth discussion, so I was quite willing to let him lead the way.

Unfortunately KMBZ does not archive their shows on the internet. I did, however, record the show for myself so that I could listen to it later. Here are reflections on my experience.

Jerry opened the show with a standard introduction:

Should we teach evolution? … and evolution only? Should we teach creation? … creation only? Should we teach both? … and trust that young people can actually make up their own minds, given all, or at least both, of the two prevalent theories of the world.

Now, one of my purposes for going on this show was to try some different approaches to discussing evolution with those that don’t accept it. Instead of letting myself be put on the defensive, I wanted to be more proactive. Therefore, early in the show, I asked Jerry,

What exactly about evolution do you not accept? Do you not accept there has been common descent?

After verifying that he accepted an old earth - Jerry is not a young-earth creationist, Jerry said,

I have no problem with adaptation within species. That can be proven. But you can take thousands of generations of e. coli bacteria and still come up with nothing more than e. coli bacteria. There’s been no demonstration that I’ve been able to see, other than theory*, of a species becoming another species.

* As Jerry and I discussed later in the show, he was using the word “theory” here in the common sense of speculation or unproven guess. This confusion between the common meaning and the scientific meaning of “theory” continued throughout the show

So now we had the basic issue before us: “macroevolution” - evolution of species, is an undemonstrated and speculative guess, and therefore common descent is also.

Then I started to ask Jerry another question:

If you don’t think that evolution can take us beyond species, then a scientist has to ask, “what’s the alternative explanation.” What do you think has happened to create …,

but Jerry interrupted me with,

No, wait a minute. I don’t have to have developed a workable theory of how the earth was formed, how the various species came to be, in order to think evolution is wrong.… Just because I don’t have a theory that is better than evolution doesn’t mean evolution is right*.

(*By the way, Jonathan Wells gave this same response when I asked him the same question at the IDnet’s 2002 DDD conference.)

I spent the next few minutes discussing the fact that scientists for over 150 years had been testing the theory of evolution and its competing predecessor theory, special creation, against the evidence, and that overwhelmingly the theory of evolution had been accepted and special creation had been rejected.

Again, Jerry resisted this attempt on my part to look at “the competing hypotheses” - to compare evolution with some other explanation. At some point, he said,

But you’re trying to bring this back to “you guys who believe in creation are wrong.” I’ve never told you I believe creation is the correct explanation. I’ve told you that I don’t think your theory has proven itself out completely.

But later he added,

Why does so much almost religious zeal come from evolution people such as yourself to avoid talking about any other theories.

Now notice the inconsistency here. On the one hand, the point that one doesn’t have to know what is right to think something else is wrong has some legitimacy - the conclusion “I don’t know” is an accepted position in science.

On the other hand, notice that it is Jerry who is avoiding discussing these other theories! He starts the show asking if we should teach evolution, or creation, or both; he then says that he doesn’t have an alternative theory, hasn’t taken a position on creation, and doesn’t need to to critique evolution; but then he berates me (religious zeal being a pretty strong term) for not being willing to discuss the alternative theories.

But comparing evolution with its alternative, special creation “theory”, had been exactly what I was trying to do, and he wouldn’t do it.

Later in the show I made this point explicitly, and the conversation went like this:

Krebs: “Here’s an inconsistency in your position I’d like to bring up. You have said we should teach other theories other than evolution in …”

Agar: “No I didn’t.* I said you should be open to them and not as close-minded as I see the scientific community being, and again, I’m not saying this is an either-or thing. I’m wanting you to demonstrate that evolution is a theory proven enough that it should be so exclusive.” (*Yes he did, or at least he implied we should consider doing so in his introduction when he asked whether we should teach evolution only, creation only, or both.)

Krebs: “OK, so then what I came back with was that it can only be compared to other theories, and you said you didn’t need to have any other theory - you just had to say there’s problems with this one.”

I’ve taken the time to dissect this conversation because I think it illustrates a number of “man on the street issues.”

Notice there is a tension between wanting to “teach other theories” and wanting to teach the “weaknesses” of evolutionary theory. What many anti-evolutionists want is to show that evolution is scientifically invalid, but they really have no scientific theory to replace it with; as has been made explicit by Dembski and others, once design (or creation) is established from the invalidation of evolution, theology takes over - no more science is necessary. Therefore, they don’t really want to talk about “other theories,” because that brings up the religious ideas they are trying to avoid having me part of the discussion.

The confusion about the word theory plays into this tension. The scientific word implies that we have observations, hypotheses, demonstrated means of testing those hypotheses, etc. The common meaning of theory, however, allows one to hold a speculation or opinion without any rigorous testing against evidence. Asking them to discuss their “theory” of creation (or design) from a scientific point of view makes them uncomfortable - even such a simple question as “well, what did happen if common descent is not true” pushes a sensitive button about religion and science, and about the two meanings of theory.

So I think that if anti-evolutionists are going to ask us to “teach other theories” or even present “alternative theories,” then they need to provide positive statements and positive evidence for what they think those alternatives are.

The second idea that supported my point in this discussion with Jerry was the idea that in fact for 150 years or more, scientists had been considering the hypotheses associated with special creation and common descent. Evidence in support for common descent, while not perfectly complete (sure, there are “holes” in every theory), has accumulated to the point that the vast majority of scientists consider it a well supported theory, but evidence for special creation has been lacking. Science has been open-minded about “other theories,” but science also eventually makes judgments, and special creation has been rejected when compared to the alternative of common descent.

29 Comments

Hypothesis: Living organisms have been created in their present forms by some unseen intelligence.

Prediction #1: Organisms will continue to exist in their present forms. Prediction #1 validated by observation.

Prediction #2: When organisms go extinct they are gone forever. Prediction #2 validated by observation.

Happy now?

Good work J Low! Nothing to see here science, move along.

J Low:

Sorry. Your prediction #1 has been proven false many times over. For example, dog breeding has produced new sub-species that never existed before, invalidating your false “present forms” argument. For a more “undirected” example, the average height of humans has increased noticably over the last few centuries, and certain breeds of birds (I forget which one) has shown a measurable legthening in the tail feathers of the male birds even though it is counter-productive to their flying skills due to sexual preference of the females. Both these are example disproving the “present forms” argument.

Prediction #2 is also predicted by evolution. It is HIGHLY improbable that the same species would evolve twice.

I had the privilege of listening to Jack Krebs on the Jerry Agar Show on 12/30/04. I thought Jack did a great job of slowing Jerry’s gallop and forcing him to respond to some important questions.

I thought the discussion was especially interesting when it was revealed that Jack is a layperson (a professional educator) and not a practicing scientist. As I remember, Jerry then questioned whether Jack was truly qualified to be arguing on behalf the scientific community (or something to that effect). In response, Jack clarified by saying that he is a “well-educated layperson.” To this, Jerry said something like, “So I’m just stupid, then, huh?” Of course, Jack did not intentionally imply this, but Jerry’s response was revealing.

Like Jerry Agar, a lot of people are “armchair scientists” who claim to know enough about the theory of evolution to know that it has not, in Jerry’s words, “proven itself out completely.” But, when challenged to substantiate their claims, these “armchair scientists” are almost always unable to do so. Jerry revealed so many personal misconceptions about evolution in this hour-long segment that, in my opinion, it could take years to set him straight.

As a “well-educated layperson,” Jack Krebs knows a lot about how science works and what scientists actually do. In a way, Jack is like an experienced sports broadcaster whose informed opinions are respected because he has spent a lot of time around the “sport” of science.

So, to complete the analogy, I ask this question:

Who’s more qualified to make pronouncements about sports: the guy next door who yells at his TV when he disagrees with a call or the experienced professional broadcaster who has studied and researched the sport he describes?

Although both are not athletes themselves, it should be very clear who is the most qualified. Unfortunately, our educational system seems to have produced too many “armchair scientists” and not enough “science broadcasters.” Thanks, Jack, for your efforts.

J Low Wrote:

Hypothesis: Living organisms have been created in their present forms by some unseen intelligence.

For a sufficiently vague hypothesis, anything can be claimed as proof.

J Low,

Before one tests hypotheses, one must first have a theory from which these hypotheses are derived.

Any theory to be considered as science must meet these minimum requirements. It must be:

1. Internally consistent 2. Experimentally verifiable 3. Predictively useful

ID advocates have failed to produce such a theory on all counts. 1. IDers are all over the place when it comes to agreeing how much evolutionary theory (if any) they are willing to accept before ID “kicks in.” The irreducible complexity (IC) formulation, which is to provide an “objective” measure supporting their propositions, contains an “R” factor, or “rejection region” which allows for the dismissal of signs of complexity which are “obviously” a result of natural causes, not ID. And who determines what falls into this rejection region? Why it’s the ID investigator himself! As more natural causes fill in these “gaps,” and enter the rejection region, ID “theory” eventually evaporates into thin air. 2. With no cogent theory, there are no hypotheses available to test. No research can be done. No results can obtain. Colloquially speaking, there is no “there” there. 3. Saying “God did it” whenever we find a gap in our knowledge provides us with no useful way to proceed. Information theory tells us that the information content of a message is related to its unpredictability. If “God did it” is the answer every time, then the information value is zero. Since ID does not meet these three criteria, it is not science.

Jack, it’s excellent how you caught Jerry on his double standard, but I wish you hadn’t used the creationist weasel word “special creation.” As you know, when cornered, anti-evolutionists sometimes admit that SC does not necessarily exclude common descent. And by suggesting the old false dichotomy, SC is meaningless at best, misleading at worst. FWIW, I usually say “independent abiogenesis.” While anti-evolutionists know that, if it’s not CD it must be more abiogenesis, they can’t very well say that and try to prove abiogenesis “impossible” (using bogus calculations) at the same time. So weasel words it is every time. “Common design” is another of my favorites.

jeff-paredo

Birds with longer tail feathers are still birds.

A Chihuahua and a Saint Bernard are both still dogs. After a 20,000 year long experiment where dog populations were isolated and selected for adaptation to many different environments from hunting to herding to companionship not one new species of dog has emerged. They’re all still dogs and if you mix the breeds back together you’ll get the wolf from whence they all descended beginning 20,000 years ago.

Using this empirical evidence of adaptation to infer a mechanism that caused a single celled universal ancestor to morph into things as diverse as trees and the dogs that mark them seems like an unreasonable extrapolation to me.

20,000 years out of 4 billion years… Wow, even in this evolutionary short period of time, much variation has arisen. Of course we call them still dogs, what else would you have expected?

As far as new species of dogs emerging, I am not sure what you are trying to say here.

Perhaps you should familiarize yourself with that which you oppose?

David Scott Springer is apparently not aware of the age of the St. Bernard and Chihuahua breeds. Nor has he ever attempted to mate a St. Bernard and a Chihuahua. Nor is his mind capable of appreciating the difference between 20,000 and 2 billion. And he clearly doesn’t know very much about biology or evolutionary theory.

Nevertheless, he is eager to troll this blog and let us know that he believes that the vast majority of the world’s scientists are unreasonable for subscribing to a theory that has proven powerful and predictive for the last 150 years in spite of the near-constant challenges from incredulous cranks like David Scott Springer.

I would recommend Richard Dawkins’ latest book, The Ancestor’s Tale to you, David. It explains in wonderful detail the very large lengths of time that species have been diverging on the planet, as well as the rough temporal order and pattern of their separation. It’s a fascinating book, and has given me a far better sense of the course of life on the earth than I had ever had before.

I found some info

Chad Davis, KNME program manager, said the show lists five Christian organizations as funders, including the Crowell Trust, whose Web site says it promotes “the teaching and active extension of the doctrines of evangelical Christianity through approved grants to qualified organizations.”

Fascinating

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Dave Scott

“Birds with longer tail feathers are still birds. A Chihuahua and a Saint Bernard are both still dogs.”

The physical differences between a Chihuahua and Saint Bernard are arguably greater than the differences between a Human and a Chimp. So using your logic Humans and Chimps haven’t evolved because they are still both “apes”.

J Low your arguements are not very good.

J Low Wrote:

Hypothesis: Living organisms have been created in their present forms by some unseen intelligence.

Prediction #1: Organisms will continue to exist in their present forms. Prediction #1 validated by observation.

See Birth of a unique enzyme from an alternative reading frame of the preexisted, internally repetitious coding sequence.

J Low Wrote:

Prediction #2: When organisms go extinct they are gone forever. Prediction #2 validated by observation.

See Tasmanian Tiger Cloning Breakthrough

So not only do we have a organism continuing in a new form but we are one step closer to bring back an extinct organism. Hmmm does this mean your God Theory is wrong and God does not exsist?

Perhaps you’d like to make some positive assertions like

Prediction #3: Jesus will come down from the sky and sweep all evolutionist into hell to burn for eternity. Atleast then you can say that your predictions just haven’t happened yet.

J Low Wrote:

Hypothesis: Living organisms have been created in their present forms by some unseen intelligence.

Prediction #1: Organisms will continue to exist in their present forms. … Prediction #2: When organisms go extinct they are gone forever.

Your predictions do not follow from your hypothesis.

Nic George

“The physical differences between a Chihuahua and Saint Bernard are arguably greater than the differences between a Human and a Chimp.”

What do you propose is stronger evidence of common descent between groups of organisms than ability to breed and produce fertile offspring?

I’d be happy to hear just one (falsifiable) prediction made by a “Creationist Model” rather than having facts explained post-hoc. Did Creationism predict what has been found in the Grand Canyon? Or has Creationism tried to explain those finding post-hoc by resorting to “novel” (I’m being generous) ideas about the dynamics of water flow? Or how about the similarities in genetic makeup between species believed to be in “close” proximity on the “tree of descent?” Did Creationism predict that this would be the case? Or have they resorted to a post-hoc explanation, which says that “sure, God could have done it that way.”

If a God had anything to do with the world around us, “he” indeed could have “created” it any way “he” wanted to. But, that’s not the question. The question is: If there is a Creationist Model that wishes to be taken seriously by scientists, it must posit predictions about what we should (and should not) find if the Model is accurate. It should also be falsifiable in theory – that is, it should tell us how we can know if the theory is mistaken in some way.

What do you propose is stronger evidence of common descent between groups of organisms than ability to breed and produce fertile offspring?

[devils advocate]Why should that be evidence of common descent? Maybe G– oops, the Intelligent Designer, made some species with the ability to cross-breed. Horses and donkeys cross-breed to produce mules, rarely a is fertile. Lions and tigers can cross-breed, the females are fertile. A few years ago someone produced a camel-llama hybrid. [/devils advocate]

As for the strongest evidence of common descent, how about the genetic sequence data pouring out of genome sequencing labs today? Not only does ‘molecular clock’ evidence give nearly the same phylogeny as derived from anatomical comparisons and the fossil record, but detailed analysis of the genetic differences LOOKS JUST EXACTLY AS IF IT DERIVED FROM COMMON DESCENT. I.e. the sequences were not simply re-used, unless G– oops, the Intelligent Designer, deliberately re-used them while giving them the appearance of common descent, e.g. individual mutations, insertions, rearrangements, etc can be traced down phylogenetic lines, making work like this possible:

Reconstructing large regions of an ancestral mammalian genome in silico Mathieu Blanchette, Eric D. Green, Webb Miller and David Haussler Genome Research 14:2412-2423, 2004

To quote George Tenet, “It’s a slam dunk”.

Dave like Bayesian Bouffant points out there are many species that can interbreed and produce fertile offspring. The level of viability (how often a live birth happens in these cross breeding situations) and level of fertility (how often the offspring are fertile) are show an indication of common descent. The longer ago the common ancestor (in genetic change timeframe) the less viable and fertile the offspring become (in a very generic sense. We would expect to see species with a recent common ancestor to have a high fertility rate. As we look at species with older (again in genetic change terms) common ancestors the fertility rate starts dropping and the viability rate starts dropping.

For 2 species of Equus. Equus Przewalski and Equus caballus Equus caballus (domestic horse) have 64 chromosome Equus Przewalski (Przewalski Horse) has 66 chromosomes

These 2 species can interbreed with very high fertility and viability rates. There is some debate if the Equus caballus was derived from the Equus Przewalski line ( ie that Equus caballus branched off this line) Note that this doesn’t mean that the Equus Przewalski has not changed genetically in the time since the divergence. Other speculations put them as descendants of Equus ferus. Note the linage is always being looked at and there are debates about exact placements and relationships of species.

The point is that these 2 species are different genetically but interbreed very well. Equus Asinus (donkeys ) have a 62 chromosome and show common ancestor much further back. The viability rate of Equus caballus/Equus asinus hybrids is fairly high while fertility is very low.

Equus Heionus (Asian donkeys) have chromosome counts in the 50s dependant of the specific species you are looking at. Again viability rates are good but fertility rates are not known (ie I can not find any confirmed fertile offspring documented)

Equus Grevi have 46 chromosomes, Equus Burchellii have 44 chromosomes and Equus Zebra have 32.

It is interesting to note that the genetic changes get more dramatic when you look at them geographically from where the ancient migration route is came from the north and migrated south.

Grevi and Burchellii territory overlap yet natural interbreeding is not know to occur. The Equus Zebra is very geographically isolated in the southern portions of Africa they are also the most different genetically from the domesticated horse.

All of these species can interbreed and their viability and fertility rates are what you would expect of common descent

If you took a population of any one of these species and isolated them from their parent species for a few million years you would see a new species slowly emerge. There isn’t any line where a species is suddenly another. Species are soft grey areas where we, humans, place life into groups.

Agian as Bayesian Bouffant points out with genome sequencing we’ll start to see more and more evidence of how species are related. Some reclassification might occur with regard to species but this will mostly occur within genus, species and subspecies.

Let me say one more thing to clarify what Bayesian said.

Bayesian Bouffant Wrote:

individual mutations, insertions, rearrangements, etc can be traced down phylogenetic lines, making work like this possible:

Say 50 million years ago a mutation occured in a population. As that populations diverged into many species we would expect all of the species to have that mutations until it was altered by another mutation. It is predictions like this that are being proven true by genome sequencing. The only way to explain this by use of a “designer” is to say that the “designer” created the first life then through out time took populations and made changes to them genetically while splitting thes populations off into other populations that later would get other genetic modifacations but those changes would not be made to the 1st population. So its kind of like having the designer say “Hey I’ve got this new idea for this species!” then the designer goes and makes the change in 1 population of the species but not another. Hmmm maybe the designer is just doing tests.….BILLIONS of tests at the same time.

Dawkins, in ‘The Ancestor’s Tale’ talks about two “ring species” (or whatever he calls them), one example is a ring of newts around a California lake, the other a ring of gulls around the Arctic Circle. In each case, there is an area where two entirely different species are found, which are not capable of interbreeding at all. Travel around the circle, however, and you find a sequence of species, each of which interbreeds (at least a little) with its neighbor. Indeed, it’s only taxonomically convenient to call these populations separate species. What is found in both cases is a continuous spectrum of variation, with interbreeding with the neighbors occuring continuously around the ring, except at the “end”. Clearly, the two representatives at the “end” are completely different species. But where along the ring do they become separate? How many different species should be designated along this spectrum? Justify your answers!

Steve Jones’ Darwin’s Ghost makes much the same point. Another distinction is the time over which evolution operates. Does it count if the two species interbreed but the hybrids are 10% less fertile as the isolated ancestors? The hybrids are doomed; gone in

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Wayne Francis:

The only way to explain this by use of a “designer” is to say that the “designer” created the first life then through out time took populations and made changes to them genetically while splitting thes populations off into other populations that later would get other genetic modifacations but those changes would not be made to the 1st population.

Technically, that’s not the ONLY way to explain it. As I mentioned, it could be that the Intelligent Designer created all the various species quite recently with the appearance of common descent, and buried all those fossils in the ground, created the photons on their way from those galaxies 13 billion light-years away, etc. This argument was advanced once by a Creationist geologist (Price?) and didn’t seem to go over well at all among proponents of either evolution or creationism.

true Bayesian Bouffant there is never just 2 ways to look at things. Thanks for correcting me.

One thing that should be made clear is while hybridizing could result in a population that brings forth a new species it does not appear to be the norm. Grevi and Plains zebras are a good example. Their territory overlap and often you see mixed grazing herds but these 2 species don’t interbreed in the wild. The creationist argument, used to distort the issue, that interbreeding would cause the population to become extinct is useless. The point is genetically they can interbreed with less viability and fertility which indicates that in the distant past these 2 species where 1 and split at which point they started accumulating different mutations. Over time these different mutations has made interbreeding less successful.

The “appearance of age” argument goes back to Gosse’s “Omphalos” published in 1857, two years before Darwin’s “Origin of Species”. The specific application of photons created close to Earth to give the appearance of ancient stars is, of course, more recent.

The “appearance of age” argument goes back to Gosse’s “Omphalos” published in 1857, two years before Darwin’s “Origin of Species”. The specific application of photons created close to Earth to give the appearance of ancient stars is, of course, more recent.

Thanks. That would be zoologist Philip Gosse. Omphalos, ISBN 1881987108, is remarkably enough available for sale at Amazon.com.

I read about it in Martin Gardner’s classic Fads and Fallacies, ISBN 0486203948, specifically chapter 11: Geology versus Genesis. This classic is highly recommended. In addition to the chapter on Creationism, the next chapter is on Lysenkoism, which should also be of interest to anyone involved in the ID debate. Fads and Fallacies is still remarkably relevant over half a century after its initial publication.

j lo: loved you in “The Cell” and “Selina”, but lately… sorry, you’re faltering

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This page contains a single entry by Jack Krebs published on January 8, 2005 2:06 PM.

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