24 October 2007

They selected teosinte...and got corn. Excellent!

Evolutionary science is so much bigger, so much deeper, so much more interesting than its opponents (understandably) will admit. It's more complicated than Michael Behe or Bill Dembski let on, and yet it's not that hard to follow, for those who are willing to try. The best papers by evolutionary biologists are endlessly fascinating and scientifically superb, and reading them is stimulating and fun.

Yet, as an experimental developmental biologist reading work in evolutionary biology, I often find myself yearning for what we call "the definitive experiment." Molecular biology, for example, can point to a few definitive experiments -- elegant and often simple -- that provided answers to big questions. Sometimes, while examining an excellent evolutionary explanation, I think, "Wouldn't it be great if they could do the experiment?"

Now of course, plenty of evolutionary biology is experimental, and I've reviewed some very good examples of experimental evolutionary science on this blog. But when it comes to selection and the evolution of new structures and functions, the analysis often seems to beg for an experiment, one that is simple to conceive but, typically, impossible to actually pull off -- there's not enough time. The previous Journal Club looked at one way around this limitation: bring the past back to life. Even better, though, would be to find an example of evolutionary change in which the new and old forms are still living, so that one could do the before-and-after comparison. It would look something like this: take a species, subject it to evolutionary influences of some kind until the descendants look significantly different from the ancestors, then compare the genomes (or developmental processes) of the descendant and the ancestor, in hopes of discovering the types of changes at the genetic or developmental level that gave rise to the differences in appearance or function of the organisms. That would be a cool experiment.

In fact, that kind of experiment has been done, more than once. The best example, in my opinion, involves an organism far less sexy than a dinosaur or a finch or a whale: Zea mays, better known as corn (or maize).

Corn is a grass, but a grass that's been so extensively modified genetically that it's barely recognizable (to non-specialists like me) as a member of that family. Wait...genetically modified? Yes, and I'm not talking about the really modern tricks that gave us Bt corn or Roundup Ready corn. In fact, the wonderful stuff they grow in Iowa is quite different from the plants that humans first started to harvest and domesticate in Central America a few millenia ago. Corn as we know it is the result of a major evolutionary transformation, driven by selection at the hands of humans. (I don't find the natural/artificial selection distinction at all useful, since there's no explanatory difference, but you can refer to the selection under consideration here as 'artificial' if it makes you feel better.) The story has been a major topic in evolutionary genetics for decades, but it's largely absent from popular discussions, probably because the Discovery Institute has wisely avoided it. I hope it will soon be clear why you won't find the word 'teosinte' anywhere at discovery.org.

For many years, the origin of corn was a mystery. Like most known crops, it was domesticated 6000-10,000 years ago. But unlike other crops, its wild ancestor was unknown until relatively recently. Why this odd gap in our knowledge? Well, it turns out that corn is shockingly different -- in form, or morphology -- from its closest wild relative, which is a grass called teosinte, still native to southwestern Mexico. In fact, corn and teosinte are so different in appearance that biologists initially considered teosinte to be more closely related to rice than to corn, and even when evidence began to suggest a genetic and evolutionary relationship, the idea was hard to accept. As John Doebley, University of Wisconsin geneticist and expert on corn genetics and evolution, puts it: "The stunning morphological differences between the ears of maize and teosinte seemed to exclude the possibility that teosinte could be the progenitor of maize." (From 2004 Annual Review article, available on the lab website and cited below.)

But it is now clear that teosinte (Balsas teosinte, to be specific) is the direct ancestor of corn. In addition to archaeological evidence, consider:
  • The chromosomes of corn and teosinte are nearly indistinguishable at very fine levels of structural detail.
  • Analysis using microsatellite DNA (repetitive DNA elements found in most genomes) identified teosinte as the immediate ancestor of corn, and indicated that the divergence occurred 9000 years ago, in agreement with archaeological findings.
  • Most importantly, a cross between corn and teosinte yields healthy, fertile offspring. So, amazingly, despite being so different in appearance that biologists initially considered them unrelated, corn and teosinte are clearly members of the same species.
The basic idea, then, is that corn is a domesticated form of teosinte, exhibiting a strikingly distinct form as a result of selection by human farmers. And that means that we have a perfect opportunity to examine the genetic and developmental changes that underlie these "stunning morphological differences." We can do the experiment.

First, have a look at an example of one of the evolutionary changes in teosinte under human selection.

The small ear of corn on the left is a "primitive" ear; the brown thing on the right is an ear from pure teosinte. (Both are about 5 cm long.) The "primitive" ear is similar to archaeological specimens representing the earliest known corn. Image from John Doebley, "The genetics of maize evolution," Annual Review of Genetics 38:37-59, 2004. Article downloaded from Doebley lab website.

The thing on the far left is a teosinte "ear," the far right is our friend corn, and the middle is what you get in a hybrid between the two. Photo by John Doebley; image from Doebley lab website.

The pattern of branching of the overall plant is also strikingly different between corn and teosinte, and you can read much more on the Doebley lab website and in their publications.

When I first heard about this work at the 2006 Annual Meeting of the Society for Developmental Biology, I was astonished at the amount of basic evolutionary biology that was exposed to experimental analysis in this great ongoing experiment. Here are two key examples of the insights and discoveries generated in recent studies of corn evolution.

1. Does the evolution of new features require new, rare, mutations in major genes?

Perhaps this seems like a stupid question to you. Anti-evolution propagandists are eager to create the impression that evolutionary change only occurs when small numbers of wildly improbable mutations somehow manage to help and not hurt a species. And in fact, experimental biology has produced good examples of just such phenomena. But there is at least one other genetic model that has been put forth to explain the evolution of new forms. This view postulates that many major features exhibited by organisms are "threshold" traits, meaning that they are determined by many converging influences which add together and -- once the level of influence exceeds a threshold -- generate the trait. The model predicts that certain invariant (i.e., never-changing) traits would nevertheless exhibit significant genetic variation, since evolutionary selection is acting on the overall trait and not on the individual genetic influences that are added together. Hence the implication that...
...populations contain substantial cryptic genetic variation, which, if reconfigured, could produce a discrete shift in morphology and thereby a novel phenotype. Thus, evolution would not be dependent on rare mutations, but on standing, albeit cryptic, genetic variation.
--from Nick Lauter and John Doebley, "Genetic Variation for Phenotypically Invariant Traits Detected in Teosinte: Implications for the Evolution of Novel Forms," Genetics 160:333-342, 2002.
In that paper, the authors show that several invariant traits (e.g., number of branches at the flower) in teosinte display significant genetic variation. In other words, the traits are the same in every plant, but the genes that generate the traits vary. The variation is 'cryptic' because it's not apparent in basic genetic crosses. But it's there. The authors ask: "How can cryptic genetic variation such as we have detected in teosinte contribute to the evolution of discrete traits?" Two ways: 1) the variation is available to modify or stabilize the effects of large-effect mutations; and 2) variation in multiple genes can be reconfigured such that it adds up to a new threshold effect. Note that the first scenario is clearly applicable to the kind of evolutionary trajectory outlined by Joe Thornton's group and discussed in a previous post. The second scenario is particularly interesting, however, since it addresses an important question about the role of selection. Consider the authors' discussion of this issue:
At first glance, cryptic variation would seem inaccessible to the force of selection since it has no effect on the phenotype. However, if discrete traits are threshold traits, then one can imagine ... that variation ... could be reconfigured such that an individual or population would rise above the threshold and thereby switch the trajectory of development so that a discrete adult phenotype is produced. We find this an attractive model since evolution would not be constrained to “wait” for new major mutations to arise in populations. (Italics are mine; ellipses denote deletion of technical jargon, with apologies to the authors.)
In fact, in a 2004 review article, Doebley is bluntly critical of the assumption that new mutations were required during the evolution of corn, and seems to suggest that this view led researchers significantly astray:
There is an underlying assumption in much of the literature on maize evolution that new mutations were central to the morphological evolution of maize. The word "mutation" is used repeatedly to describe the gene changes involved, and Beadle led an expedition ("mutation hunt") to find these rare alleles. The opposing view, that naturally occurring standing variation in teosinte populations could provide sufficient raw material for maize evolution, was stated clearly for the first time by Iltis in 1983. Although new mutation is likely to have made a contribution, anyone who has worked with teosinte would agree that teosinte populations possess abundant genetic variation. [...] Allowing for cryptic variants and novel phenotypes from new epistatic combinations to arise during domestication, it is easy to imagine that maize was domesticated from teosinte.
--John Doebley, "The genetics of maize evolution." Annual Review of Genetics 38:37-59, 2004.
Compare that discussion, and others like it in the paper I'm quoting, with the yapping about mutations that passes for anti-evolution criticism of evolutionary genetics. I can find no evidence that Michael Behe or any other ID theorist has even attempted to seriously address the importance of genetic variation in populations. I haven't read The Edge of Evolution yet, but I have it right here, and the index suggests that Behe hasn't tried to engage genetics beyond the high school level. There's a good reason why Behe is an object of scorn in evolutionary biology. He wants you to think it's because his critics are mean. No; it's much worse than that.

2. Does evolutionary change ever result from a "gain of information," or does Darwinian evolution merely prune things out?

It would be easy to get the impression from various creationists and ID proponents that mutation and selection can only remove things from a genome. Young-earth creationist commentary on "microevolution" (a yucky term for the now-undeniable fact of genetic change over time) always adds that this kind of change involves NO NEW INFORMATION. (The caps are important, apparently, since caps and/or italics are de rigueur in creationist denialism on this topic.)

Similarly, Michael Behe wants you to think that beneficial (or adaptive) mutations are some kind of near impossibility, and that when they do happen it's almost always because something's been deleted or damaged, with a beneficial outcome.

Studies of evolution in corn and teosinte (and other domesticated plants), not to mention findings like the HIV story on Abbie Smith's now-famous blog, tell a different -- and, of course, more wonderfully interesting -- story. In a minireview on the genetics of crop plant evolution in Science last June, John Doebley notes that most of the mutations that led to major evolutionary innovations occurred in transcription factors, which are proteins that turn other genes on and off. Then this:
Another remarkable feature of this list is that the domesticated alleles of all six genes are functional. If domestication involved the crippling of precisely tuned wild species, one might have expected domestication genes to have null or loss-of-function alleles. Rather, domestication has involved a mix of changes in protein function and gene expression.
In other words, the new genes are not dead or damaged; they're genes that are making proteins with new functions. ('Allele' is just the term for a particular version of a particular gene, and 'null', as you might have guessed, is a version that is utterly functionless, as though the gene were deleted entirely.) Now, if you've even flipped through The Origin of Species, you might not be surprised by Doebley's conclusion:
Given that the cultivated allele of not one of these six domestication genes is a null, a more appropriate model than "crippling" seems to be adaptation to a novel ecological niche -- the cultivated field. Tinkering and not disassembling is the order of the day in domestication as in natural evolution, and Darwin's use of domestication as a proxy for evolution under natural selection was, not surprisingly, right on the mark.
The change from teosinte to corn happened in about a thousand years. That's fast evolution. Apply selection to a varying population, and you get new functions, new proteins, new genes, completely new organisms. Fast.

So in summary, we can do the experiment. And we've done the experiment. ('We' being John Doebley and his many able colleagues.) And we've learned a lot about evolution and development. Now if we can just get people to read it. Then they'll know more about evolution, and about God's world, and about the trustworthiness of the anti-evolution propaganda machines that are exploiting the credulity of evangelical Christians.


John Farrell said...

I hate it when your posts are so good you force me to surreptitiously print these at work!

Stephen Matheson said...

:-) Thanks, John. Maybe I should prepare an article on the neurobiology of moral agency and loci of external control. At least you didn't have to worry about getting in trouble; like people in New England are going to interrupt a conversation about Josh Beckett to grump about teosinte! (BTW, check out the excellent article on the Series and the Sox in today's NY Times.)

John Farrell said...

Yes, that was an excellent piece in the Times.

But check this out for a real snap shot into the hearts and minds of Red Sox fans everywhere:


The email comments from fans are hilarious....

Monado said...

Someone once pointed out that Eurasia got emmer, which took perhaps 100 years of selective breeding to turn into wheat, and the horse; while the Americas got teosinte, which took 1000 years of selective breeding to turn into corn, and the llama.

Al Whipp said...

At least the Americas got those. You should try building a civilization on macadamia nuts.

John Reynolds said...

This does indicate that teosinte evolved into corn in some way. Probably by indigenous peoples picking the best seeds to save later. However, while it does prove evolution, it falls short in the area of speciation, as teosinte's willingness to hybridize with maize indicates (one species hybridized willingly and without help over 50% of the time in a recent study, resulting in viable offspring).

There are cases of European vegetables that look even stranger than their ancestors--consider cabbage and its variants. But none of these resulted in true speciation (i.e., the inability to hybridize successfully). That factor of evolution has never been proven, to my knowledge.

John Reynolds

Stephen Matheson said...

Speciation in plants has been abundantly documented. You could start with this review article in a recent issue of Science or a review of hybrid speciation in a recent issue of Nature. I'm not sure what you mean by "proof," but if you think there's any scientific doubt about speciation in plants, you're mistaken.

Monado said...

John, selective breeding usually produces varieties, such as the ones you mentioned. Breeders concentrate on visible differences, leaving the essentials that allow hybridization more or less intact--unlike the across-the-board changes that occur in the wild. More interesting, perhaps, is the complete review of North American birds, which found that about 90% of them were true species as we had assumed from morphology. Some that apprear to be separate species are still similar enough to be one; and some populations that still look the same are in fact cryptic species, too different. In other words, it's a perfect snapshot of evolution in process. You can read about it at PLoS: "Identification of birds through DNA barcodes" (preliminary study,2004) or Scientific American: "Genetic tests reveal 15 new species of North American birds" (2007).

John Reynolds said...
This comment has been removed by the author.
John Reynolds said...


Sure, speciation has been documented. But has it been observed? What I mean by proof is that, in order for two species to diverge to the point where they cannot interbreed, they must do exactly that. My contention is that such a divergence has never been observed. And since it has not been observed, it's not proven.

A few months ago, I read in National Geographic ("Was Darwin Right?") about a study through 3500 generations of fruit flies that it claimed essentially proved this cornerstone of speciation. However, the article conveniently didn't mention whether they had tried to cross one line with the other. I suspect they either didn't try, or were successful in doing so (and therefore unsuccessful in proving the theory). Otherwise, this would have been big news, and not just an editorial comment.

There's no doubt to me that teosinte is either maize's ancestor or at least closely related. But how can it be cited as evidence of speciation (i.e., to the point of reproductive incompatibility), when maize is still being backcrossed against teosinte in the search of better corn varieties?


I've read a lot about the evolution of bird species classification. Several American species have a hybridization band along the rocky mountains. So it's easy to imagine that these species have a singular ancestor. But they do hybridize, and generate viable offspring. So this doesn't prove true speciation, either.

I think that if finches evolved to different species that can interbreed, such species could be varieties. But maybe they just have compatible DNA. I would think that by now, if it were possible for two lines to evolve out of compatibility with each other, it should be provable.

Stephen Matheson said...

John Reynolds writes, in reference to speciation:
"My contention is that such a divergence has never been observed. And since it has not been observed, it's not proven."
This is not a criticism of evolutionary theory. It's a rejection, by you, of at least one of the basic assumptions of science. (I'm thinking of the uniformity assumption, as well as the assumption that unobservable phenomena are not necessarily unknown or unknowable.) To see why your objection is not a serious one, apply it to moon craters. Your criteria must lead you to conclude that any claim regarding the causation of these phenomena is unproven. No one, with the possible exception of the late Henry Morris, would take such a semantic point seriously.

So, if you wish to state that speciation is "unproven" because it's never been observed, go ahead, but don't assume that you've raised an interesting or important objection to scientific understandings of evolution, moon craters, fossils, early human development, or any other phenomenon in God's world that hasn't been seen by human eyes.

John Reynolds said...


>This is not a criticism of
>evolutionary theory. It's a
>rejection, by you, of at least one
>of the basic assumptions of science.

Does the scientific method allow for assumption?

>No one [snip] would take such a
>semantic point seriously.

I didn't realize I was being semantic. Deciding what to take seriously (i.e., believe) in absence of proof, imo, is what is wrong with part of the scientific community with regards to the origin of life.

> don't assume that you've raised
> an interesting or important
> objection to scientific
> understandings of evolution,
> moon craters, fossils, early human
> development, or any other
> phenomenon in God's world that
> hasn't been seen by human eyes.

I don't know how important, interesting or new my objection is to scientific understandings of evolution. I would imagine that there are others who agree with me. I don't have objections to moon craters or fossils, however. :)


Stephen Matheson said...

John Reynolds:
"Does the scientific method allow for assumption?"
Science does not merely 'allow' for assumption. It depends on a set of foundational assumptions about the universe and the nature of reality. Uniformity and intelligibility are two examples. This is pretty basic philosophy of science, something you should consider reading more about. I recommend Del Ratzsch's book; see the links on my blog.

My reference to your claims regarding 'proof' as 'semantic' were an attempt on my part to be generous. The point is that if you really think that scientific 'proof' is utterly dependent on human observation, then you would conclude that the assertion that moon craters were caused by meteorite impacts is unproven. Semantically, working from your definition, this is true, and it's also quite silly. Ditto for the events of human embryonic development, almost none of which have ever been observed.

For your objection to be anything more than a painfully contrived attack on evolutionary theory, you need to stand by your definition of "proof" in every scientific context. And when you do that, in my view, your complaint will not be taken seriously, because it's based on a wholly misguided view of what scientific explanation is all about.


John Reynolds said...


>For your objection to be anything
>more than a painfully contrived
>attack on evolutionary theory, you
>need to stand by your definition
>of "proof" in every scientific

I don't have to do that. And my objection isn't contrived. It's a valid objection that I have and share with others.

I'm not calling science into question. I'm calling into question the dogmatic assumption that, because organisms can evolve, new species result that can't breed with separate lines from the same parent. But I'm not saying it isn't possible. All I'm saying is that it has not been scientifically proven and that I don't believe evolution works to that extent.

>And when you do that, in my view,
>your complaint will not be taken
>seriously, because it's based on a
>wholly misguided view of what
>scientific explanation is all

Exactly. Which is why (I assume) you want me to demand proof on moon craters and [the age of] fossils. But I'm not claiming all science is wrong. So I'm not going to attack what seem to me to be sound, reasonable assertions.

Speciation does not make sense to me. Why is it that even separate fruit fly lines (or the lines represented by teosinte and maize) won't evolve to the point of incompatibility with each other? I've heard this called a sudden process, like a switch being turned on. That sounds contrived to me.


Monado said...

Sorry, perhaps you haven't heard of Culex molestans? It's a new species of mosquito, descended from surface-living mosquitoes, Culex pipiens that were trapped when the London subway was built. It is no longer willing to breed with the surface species from which it evolved -- when the two are put together. Counting from the time when the subway was built, it has evolved into a separate species in, at most, 120 years. Someone just noticed it a couple of years ago.

John Reynolds said...
This comment has been removed by the author.
John Reynolds said...

John Reynolds said...

That is pretty fascinating. I had never heard of Culex Molestans before. I couldn't find the study your link mentioned, though it didn't say the two were incompatible. Web searches didn't turn up much. I did find a few links, including this study, which indicated that there is some natural hybridization in the southern part of this species' range. It also stated that in areas where the two species flocked together, there was mingling of genes, though at a lesser extent due to the differing mating flights of the two populations. This is because the subterranean race adapted to its environment by evolving the ability to mate in closed spaces. This change made it more difficult to mate, but didn't change genetic compatibility.

The study covered a huge area (from London to the Middle East) and that was the reason, I assume, that the people conducting the study put the captured mosquitoes in cages that were known to be too small for newly-captive populations (it is fairly well known that when mosquitoes are first captured, they need to be put in larger cages and over successive generations the cages should shrink to allow the subjects to adapt to breeding in tighter spaces). I do find it curious that they didn't figure out a way to accommodate the different mating flights of the two races, considering the nature of the study, however.

In any event, the study does acknowledge that the two species are genetically compatible. The one case in which eggs were actually laid by hybrid parents failed. But that isn't significant, especially considering the known facts admitted to by the persons involved--that the two lines are compatible.

This proves that a land race can evolve characteristics significantly different from those in its parent line. It also does seem to indicate that, over time, the two could progress to the point where they could not interbreed because of incompatibility in mating practices. However, in being able to prove two species could evolve to the point of genetic incompatibility, it falls short.


Stephen Matheson said...


This will be my last response to your comments on this topic, and you are welcome to have the last word, unless you have a question that you want me to answer. Thanks for reading my blog, and please feel free to comment more in the future.

Regarding the causation of moon craters, you wrote: "But I'm not claiming all science is wrong. So I'm not going to attack what seem to me to be sound, reasonable assertions." You have failed to address my criticism of your objections. Your original claim was that speciation is not 'proven' because it hasn't been 'observed.' It follows, whether you like it or not, that you consider the meteorite theory of causation of moon craters to be 'unproven.' I certainly understand your unwillingness to concede this point, but I am discouraged by your retreat into terms like 'sound' and 'reasonable.' The fact is that you have made several statements in this thread that indicate your relative naivete on issues related to scientific assumptions and the philosophy of science.

Your core objection, as near as I can tell, is this: "Speciation does not make sense to me." And the simplest reply is this: "Then learn more about it."

If you do this, you will find that the same evolutionary mechanisms that drove the extraordinary morphological change in maize can drive the less-dramatic changes required to achieve reproductive isolation. (In fact, proteins involved in reproduction appear to evolve quite quickly in many contexts.) And the role of reproductive isolation in the process of speciation is among the least controversial concepts in all of biology.

I surmise that you are uncomfortable with speciation for religious reasons. I sympathize, but cannot validate your concerns on that basis alone, especially since you are confused about the basic ideas behind scientific explanation. So I encourage you to continue learning about evolutionary biology and genetics, and drop the semantic protestations based on ill-defined notions of 'proof.'

Best regards,

John Reynolds said...


>This will be my last response to
>your comments on this topic, and
>you are welcome to have the last
>word, unless you have a question

At that, I was going to abstain, but after reading your post I decided there were some things I needed to answer.

>Thanks for reading my blog
I think your blog is really good, very will written, and definitely worth the read.

>Your original claim was that
>speciation is not 'proven' because
>it hasn't been 'observed.' It
>follows, whether you like it or
>not, that you consider the
>meteorite theory of causation of
>moon craters to be 'unproven.'

It doesn't follow. Meteorites have been hitting the moon for a long time. The evidence is there. It's not there for speciation.

>I certainly understand your
>unwillingness to concede this
>point, but I am discouraged by
>your retreat into terms like
>'sound' and 'reasonable.'

I'm sorry you feel that way.

>The fact is that you have made
>several statements in this thread
>that indicate your relative
>naivete on issues related to
>scientific assumptions and the
>philosophy of science.

I'm not a scientist. Science can assume whatever it likes. Assumption can be a useful tool. But a lot of people agreeing to assume a certain theory is fact, does not make it so.

>Your core objection, as near as I
>can tell, is this: "Speciation
>does not make sense to me."

My objection is that it doesn't make sense and has never been proven.

>"Then learn more about it."
I am. In fact, I've learned from this discussion.

>And the role of reproductive
>isolation in the process of
>speciation is among the least
>controversial concepts in all of

That's because it's reasonable, and sound, and proven. Until one gets to the part where two previously-compatible genetic lines become incompatible.

>I surmise that you are
>uncomfortable with speciation for
>religious reasons.

No. I do believe in God. I also believe in creation. I'm willing to keep an open mind with regard to how that mechanism actually played out. I wasn't there. But I'm not uncomfortable with speciation for religious reasons. I'm uncomfortable with it because there is a certain amount of faith required. Faith is supposed to be something that hampers the religious and closes their eyes to fact, not something that scientists are supposed to be rely on when evidence desired and expected cannot be obtained.

>you are confused about the basic
>ideas behind scientific >explanation.
Perhaps. If that is the case, maybe I should educate myself before making these arguments again. But if faith is required for scientists to take the next step, maybe it's they who have religious issues.

>[snip] and drop the
>semantic protestations based on
>ill-defined notions of 'proof.'

You're troubled by my use of words like "reasonable" and "sound." I'm troubled with the phrase "semantic protestation." I'm not twisting words. I'm simply asking for accountability and proof.



Monado said...

I think there might be a difference between Culex molestans and Culex molestus - and there's apparently another Culex molestus, which gets priority for that name, found in Australia. At least some of the popular press articles get the names confused. Unfortunately, I don't have access to the journals to follow it up. In the meantime, you might be interested in this: "Was there a War of 1812?" It shows where your line of questioning can lead.

John Reynolds said...

When I searched for Culex Molestans, Google asked, "Did you mean Culex Molestus?" I clicked on the link and figured out that I did not.

The study I cited (feel free to follow the link if you'd like) was on Culex Molestans. The reference to the enclosure size was on footnotes from another study, but was alluded to at the link.


Martin LaBar said...

Solid work! Thanks.

mohubbus said...

Hi all, I have to weigh in on this one. And just for the record codemaggot is my brother. I am fascinated by biology, microbiology, and evolution theory. However, I also am a believer in intelligent design. That said, I think John, sfmath and monado all make good points, but.....
Are you (sfmath) really trying to make the point that speciation resulting from species isolation proves evolution as the origin of life? uhhh... WHAT?!?
First off there is a specific instance of proven speciation in chipmunks in the Rocky Mountains. (sorry bro, but trust me, read on)
The original group of chipmunks could all interbreed, but there weren't always enough mates to go around at breeding season, so some chipmunks moved up the mountains in search of (what else) sex. LOL
For a while, they interbred back and forth. But eventually they became isolated by geography. Each group developed different mating patterns based on the climate, and now they are locked into specific seasons of heat. Now when the females of one group are in heat they can't even arouse 'sic' any interest from the males of the other group. So, since they can no longer interbreed, they are considered completely different species.
So sfmath it seems you win the argument......
uhhh wait.... that wasn't the original question was it?
How does that prove evolutionary origin? OH that's right, it doesn't.
Because no matter how far the two groups of chipmunks have moved from each other THEY ARE STILL CHIPMUNKS!!!!
They did NOT turn into say... birds... or... monkeys.... :-(
And while we're on the subject. I've have never received a satisfactory answer to why there aren't any apes evolving into humans right now. (or any other species) Was there a cut off date to evolution? Wouldn't the presence of a cut off date create a paradox that negated the very existence of evolution as the origin of species?
Here is the address to an article about the chipmunk study. Sorry, I don't know how to create a simple hot link here. It's my first time to this blog.

. said...

@ mohubbus:

You wrote:

speciation resulting from species isolation proves evolution as the origin of life? uhhh... WHAT?!?... uhhh wait.... that wasn't the original question was it?
How does that prove evolutionary origin? OH that's right, it doesn't.

The question was not (in this post, at least) about proof of the "evolutionary origin" of life. It was, rather, whether true speciation, defined as the inability to breed, had been "proven." John Reynolds had written:

This does indicate that teosinte evolved into corn in some way... while it does prove evolution, it falls short in the area of speciation, as teosinte's willingness to hybridize with maize indicates... There are cases of European vegetables... But none of these resulted in true speciation (i.e., the inability to hybridize successfully). That factor of evolution has never been proven, to my knowledge.

Thus, as to the question at hand, speciation due to species isolation does provide evidence ("prove") that evolutionary processes can and do result in true speciation.

You also asked:

why there aren't any apes evolving into humans right now. (or any other species)

Apes didn't evolve into humans (at least they didn't so far as my sketchy recollection of what evolutionary biology and anthropology I learned goes). Rather, apes and humans each evolved from a common ancestor. Someone more knowledgeable than I can provide the culpable party, I am sure! :-) Thus, we wouldn't expect to see apes evolve into humans, now or in the past, because both humans and living apes species are highly evolved and differently specialized descendants of that common ancestor.

As for why apes aren't evolving into other species, here are a couple of speculations – note, speculations, rather than wholesale dismissal of a very well-established theory on the basis of failing to see something with my own eyes.

First,who says they aren't? The wheels of evolution grind slowly (but they grind exceedingly fine). In 10 or 20 thousand years perhaps we'll see something that makes today's orang-outan look like a piker! :-)

Second, living apes have extreme and fast environmental changes to deal with, largely due to human effects on their habitats. Apes have other things to worry about than evolving into new species, surviving through evolution. They have to worry about getting through the next decade alive. I wonder whether the apes will make it at all, because the speed of their evolution does not seem at all up to the changes necessary to survive the environmental chaos.

We should probably stick with mosquitos and habitat-isolated chipmunks. As for those chipmunks... give 'em time. If the high-mountain chipmunks are truly, biologically incapable of interbreeding with the low-mountain chipmunks, they may well change over time. Make a note for your distant descendants to check on this – your grandchildren with as many "greats" tacked on as necessary to keep that note in the family archives for a couple of tens of thousands of years.

TheFallibleFiend said...

Creationist almost universally present a comic-book "understanding" of science as the genuine article. An example is the insistence that there is no "proof" of evolution, because "it has never been observed."

We don't have to observe things to know they occur. Not one person has ever seen gravitation. Not one person has ever seen an electron. And yet their existence is considered established fact.

Why? Because we don't have to see the thing - it is sufficient that we see its effects.

Interbreeding is not a perfect factor in determining species formation. Darwin pointed this out very clearly in OOS and brought it up repeatedly.