Wednesday, April 23, 2008

Rapid Evolution of Island Lizards

Science Daily Reports that

"'Striking differences in head size and shape, increased bite strength and the development of new structures in the lizard’s digestive tracts were noted after only 36 years, which is an extremely short time scale,' says Duncan Irschick, a professor of biology at the University of Massachusetts Amherst. 'These physical changes have occurred side-by-side with dramatic changes in population density and social structure.'"

Over the course of 36 years (roughly 30 generations) these lizards have evolved novel "cecal valves" which "slow the passage of food by creating fermentation chambers in the gut, where microbes can break down the difficult to digest portion of plants."

Cecal valves were never before reported for this species, and in fact are known in less than one percent of scaled reptiles.

This once again demolishes the creationist argument that evolution cannot "produce new information". We know it can, we have witnessed novel structures evolve.

19 comments:

Anonymous said...

Sure micro-evolution, but a lizard is still a lizard. It didn't became a chicken.

Nelix said...

Nobody said it became a chicken. But did evolve to have a handy cecal valve.

Richard said...

But i don't the whole AiG BUSTED thingy. It is great that the lizard evolved in this way. Does it prove God isn't there? Couldn't God create animals that can adopt themselfs to their enviroment?

Please explain to me the point of articles like these.

AIGBusted said...

Sure, there are believers who think that.

But AiG's claim is that mutations do not produce "new information" and that mutation and selection cannot account for the diversity of life. This claim is false.

crevo said...

Do you have any evidence that random mutations were the cause? Doesn't it seem like a little too little time for random mutations occurring in the genome to come up with a fully-formed structure?

Zach Armstrong said...

Actually, according to a paper published about theses Italian Wall Lizards Podarcis sicula,( see in Rapid large-scale evolutionary divergence in
morphology and performance associated with
exploitation of a different dietary resource
by Herrel et. al.), the two populations on Pod Kopište and Pod Mrčaru were "genetically indistinguashable" (see SI fi. 5; Herrel et. al 4792).

What this means then is that the cecal valves and other morphological features were epigenetic variations. In epigenetics, the phenotype expression can change, while the genotype remains identical. Thus, no "new" information has been added. Instead, what has happened is a change in how the genes are expressed.

According to the original paper, approximately 1 percent of reptiles include cecal valves (side note: there are around 8700 extant reptilian species (see: http://www.reptile-database.org/db-info/SpeciesStat.html), meaning that there are around 80 spedies of reptile with cecal valves) , including some Lacertid lizards besides Podarcis sicula. This suggests then that the genes that code for cecal valves may in fact be in all lacertid lizards, except the genes are not expressed, or turned "off". In the Pod Mrčaru population, adaptive pressures from the environment (i.e., lack of insects) triggered the expression of these genes.

The claim then that these cecal valves were the result of random mutations has not been tested properly. It is much more likely, looking at the facts, that environmental triggers flipped the genes to express what they were coded for: cecal valves.

While I disagree with most of the claims of Answers in Genesis, this specific example does not contradict their claim that "mutations do not produce "new information"".

However, this is a real example of evolution in action. As Richard Dawkins says, 'evolution is as much a fact as the heat of the sun'. However, even this most striking of examples does not prove the theory of abiogenesis, nor does it remove for the need of a Creator. And since no functionally new genetic information seems to have been created, the Genesis rule of organisms reproducing "after their kind" has not been violated in any way, even if it turns out the two populations could not interbreed, they are still of the same genetic "kind".

So while discovery is extremely insightful, it does not prove evolution beyond these genetic kinds, which obviously allow for much variety. This is because much of the genome in an organism is not "expressed" in each individual species, and lies dormant. Under certain selective pressures and environmental triggers, these dormant genes will become expressed as in the case of the Pod Mrčaru Italian Wall Lizards--nothing "new" then, has in reality been created, the information has just been expressed differently.

AIGBusted said...

Hey Zach,

Could you tell me where I can access a copy of the paper in question?

"What this means then is that the cecal valves and other morphological features were epigenetic variations. In epigenetics, the phenotype expression can change, while the genotype remains identical. Thus, no "new" information has been added. Instead, what has happened is a change in how the genes are expressed."

Epigenetics is not evolution, and I'm sure the sciencedaily reporters understand that. There are, however, genes which control gut formation/development. Are you saying that a change took place in those genes? If so, then this is still evolution: Genes controlling development were mutated and produced a new structure.

"According to the original paper, approximately 1 percent of reptiles include cecal valves (side note: there are around 8700 extant reptilian species (see: http://www.reptile-database.org/db-info/SpeciesStat.html), meaning that there are around 80 spedies of reptile with cecal valves) , including some Lacertid lizards besides Podarcis sicula. This suggests then that the genes that code for cecal valves may in fact be in all lacertid lizards, except the genes are not expressed, or turned "off". In the Pod Mrčaru population, adaptive pressures from the environment (i.e., lack of insects) triggered the expression of these genes."

That could be, but this could just as easily be a case of convergent evolution.

"The claim then that these cecal valves were the result of random mutations has not been tested properly. It is much more likely, looking at the facts, that environmental triggers flipped the genes to express what they were coded for: cecal valves."

I'll have to look at the paper for myself (again, can you tell me where to find it?)

"While I disagree with most of the claims of Answers in Genesis, this specific example does not contradict their claim that "mutations do not produce "new information""."

I'm not sure about that just yet, but even supposing it does there are lots of other examples in which mutation plus selection resulted in new information. Just read up on insertion mutations, or on the "nylon bug". If you search my blog I list many other examples.

"However, even this most striking of examples does not prove the theory of abiogenesis, nor does it remove for the need of a Creator."

Agreed.

crevo said...

Zach -

That's not quite correct - it was only the mitochondria that was sequenced to determine "genetic similarity". Whole-genome sequencing is REALLY expensive, and it is rarely done on two individuals so phylogenetically close.

AIGBusted said...

Hey Crevo,

Thanks for the info. I knew something didn't smell write about that guy's claim.

Zach Armstrong said...

Sorry about the mtDNA thing. I overlooked that by accident. However, my main point was to suggest that phenotypic plasticity could be responsible for this evolutionary change, rather than a "random" genetic mutation. Phenotypic plasticity happens when an organism with a fixed genotype has the ability to change its phenotype in response to a change in its environment.

A real-life example in which we know this can happen is the example of social insects, with various casts of greater or lesser degrees of morphological variation.

My main reason for the first comment is that scientist should be careful to not make dogmatic statements when the verdict is not completely in. When this happens science suffers, and banal creationist cling on like bulldogs to misstatements like these, which is both unfortunate and irritating. Similar things have happened in other cases where a commentator or scientist makes a dogmatic assertion that later proves to not be quite accurate, and the creationists come out of the wood-work. I was just trying to serve a cautionary warning to not make say that something is for certain when we don't know that for sure, so creationist misclaims, etc., will not be further fueled.

As Crevo said, the complete genome for Podarcis sicula has not been sequenced, so we do not know what kind of evolutionary change happened here, therefore, we should be hesitant to say that "new" information was produced here, because we don't know that.

Zach Armstrong said...

Oh, and the paper in question can be found here, for free: http://www.pnas.org/content/105/12/4792.full.pdf+html

crevo said...

Zach -

You are correct that it could be phenotypic plasticity. Another option to consider is that it _was_ a mutation but it _was not_ random. It may have been induced by the environment or other organisms in the environment. This is an option that Jean Lightner, the author of the AiG article you mention, would be comfortable with.

If you read Creation Research Society Quarterly, you might be interested in a paper I wrote on "randomness" in mutation theory. I have a summary of it here.

AIGBusted said...

Hi Zach,

Thanks for the link to the paper. I read it and I did see that the writers were cautious enough to say that the changes in the lizards may be due to phenotypic plasticity.

So I guess this example should not be used as an example of the evolution of something new, at least not until more research is done.

zenith66 said...

GOOD GOD, HOW can you all miss the point

the point is, evolution is blind, mutations are independent and teh enviroment doesnt exert any pressure, that is abstract human concept. The smiple fact is, that, random mutations and selection, genetic re expression AND epigentics are all unguided and stochastic changes, there fore, logially no one should expect any positive change in such short time, this is pure fiction to belive the right muattions just ahppened to come along at this particualr time..wow
thre is somethign else at work here, neither god nor evolutions mechanisms, i dont know waht it is but this totally defies explanaition by either camep

Fernando said...

Hi

I like this post:

You create good material for community.

Please keep posting.

Let me introduce other material that may be good for net community.

Source: AIG interview questions

Best rgs
Peter

Kristen Mayeaux said...

This is not macro evolution. The lizards already had the cecal valves - which are just muscles and now they are enlarged. Why not read the AIG article and even the researchers said it "Might" be evolution. Where are the genetic studies and comparisons?? This is vital to determine if there was an increase of new specified genetic information from which major changes can occur. This did not happen but was just selection of what was already in the genome. See the aid article.
http://www.answersingenesis.org/articles/2009/06/06/news-to-note-06062009

Kristen Mayeaux said...

Where is the peer reviewed literature and what does it say about new genomic information? Or is it just natural selection and adaptation? If the researchers did not do real follow up studies to determine the origin of these changes, it can be assumed that it was definitely not macro evolution.

KNOW ARMOS said...

Wow, I'm shocked to see a website where one of the most vitriolic topics on Earth are discussed in such a civil manner! I like this place :)

AIGBusted said...

Hi know armos,
Glad you like the blog. However, I have not posted here in years. Google hume's apprentice for my latest work.