Login

Join for Free!
118352 members


Experimental evidence for evolution

Discussion of everything related to the Theory of Evolution.

Moderator: BioTeam

Re: Experimental evidence for evolution

Postby StevePush » Wed Oct 13, 2010 6:34 pm

jevg wrote:
I hope my response to canolan explains more my position.
My whole point is that Darwinism is falsifiable and the evidence is showing it to be so. Since it is being falsified with evidence, and at the same time still being regarded as a scientific theory (indeed as fact) this is what has turned this hypothesis into a belief system.

You referred me to Jerry Coyne's book.
I have read a lot of it though not all and would be very happy to discus it further. This book actually proves my point and I will be quite happy to demonstrate it.

Because several days have passed since jveg offered to elaborate on jveg’s critique of Darwinian theory, I have looked to past posts for the evidence jveg has offered to provide. One study jveg cited was the long-term evolution experiment, or LTEE (See http://www.pnas.org/content/105/23/7899.full.pdf+html).

Jveg’s interpretation of the LTEE misstates what the data from the experiment actually show. The experiment was designed as a test of two alternative hypotheses: the rare-mutation hypothesis and the historical contingency hypothesis. As the name suggests, under the rare-mutation hypothesis a new trait arises as a direct result of a rare mutation. In that case the probability of acquiring the new trait remains constant over time. Under historical contingency a new trait is contingent on one or more past mutations that do not give rise to new traits by themselves but make it more likely that subsequent mutations will give rise to the new trait. In that case the probability of a new trait will start out low but rise substantial after the appearance of the “potentiating” mutation(s).

The data from the LTEE study support the historical contingency hypothesis. But since both of these hypotheses are Darwinian, the results do not falsify Darwinian theory. Even though the experiment was not designed to test Darwinian theory, the fact that a new trait arose confirms a key element of the modern synthesis of evolutionary theory.

Jveg notes that a small new trait arose in only one of 12 cultures and only after more than 30,000 generations. He estimates that would equate to 600,000 years in human generations and questions how the entire human digestive system could evolve so quickly. (That's not a good estimate because many of our ancestor species probably had generation times shorter than 20 years.) In fact, our digestive system has had a thousand times longer than that to evolve. The earliest know chordate fossil dates from 550 million years ago, and it would have already had a functioning digestive system to survive. What’s more, the field of evolutionary development has shown that small genetic changes that affect early developmental stages of an organism can have enormous effects on form and function.

Jveg also notes that the population with the new trait did not drive the parent population to extinction. Darwinian theory does not hold that the mere appearance of a new form of life necessarily means its parent population will go extinct. Closely related species and populations can coexist indefinitely. In the LTEE, the new population did not drive the parent population to extinction because the parent population was a superior competitor for glucose. What Darwinian theory does say is that over time, as environments change, some forms become extinct. The LTEE has confirmed one way in which nature generates the variation that enables such selection to occur.
StevePush
Garter
Garter
 
Posts: 22
Joined: Tue Oct 05, 2010 6:15 am
Location: Virginia, USA

Re: Experimental evidence for evolution

Postby canalon » Wed Oct 13, 2010 9:00 pm

JEVG,

First, I would like to thank you to add data to the Salem hypothesis I was curious and it is not really related to the thread, so I will not discuss further.

As for the rest of your argument, other have once again demonstrated, and better than I would, that your understanding of the experiments that demonstrate the falsification of the theory of evolution is slightly out of touch with what others (including the author of such work) think they mean.
And I would suggest that the theory of evolution by natural selection is still not perfect, and there are a lot of things that are not understood, but scientist are working on that and expanding and improving our understanding of how individuals are changing. All in all the theory is the best model we have, it makes predictions that er generally verified, and I would be curious if you had any other system that would perform better. As T. Kuhn in the 'structure of scientific revolution' you need more than just pointing problems to overturn a model that work because scientist will keep adding epicycle to make it work, you need to provide a whole model that work better. I am still waiting for a hint of that. For the moment you have limited yourself to say that the creator hypothesis is as credible as random mutations fully ignoring the hidden complexity. So what else do you have in store, besides "I refuse to understand and listen how it works, I refuse to admit it, you biologists are wrong"?
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
User avatar
canalon
Inland Taipan
Inland Taipan
 
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm
Location: Canada

Re: Experimental evidence for evolution

Postby jevg » Mon Oct 18, 2010 11:49 am

My apologies for not responding to the last few posts.

I have been otherwise engaged not the least of which is a back injury I have sustained. However I am back again. I will catch up with the posts and continue shortly. I notice Stevepush has put up an appraisal of the LTEE experiment . I will study it and respond.

btw I am glad to add data to the Salem hypothesis. Always good to be of help :)
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom


Re: Experimental evidence for evolution

Postby StevePush » Mon Oct 18, 2010 2:09 pm

jevg,

I'm so sorry to hear about your back injury. I'm glad you're feeling better.

Best regards,

Steve
StevePush
Garter
Garter
 
Posts: 22
Joined: Tue Oct 05, 2010 6:15 am
Location: Virginia, USA

Re: Experimental evidence for evolution

Postby jevg » Tue Oct 19, 2010 6:12 pm

Hi Steve

Thanks very much for your kind thoughts. Happily my wife is a nurse although she does come over as matron more often than not. :)

jveg’s interpretation of the LTEE misstates what the data from the experiment actually show. The experiment was designed as a test of two alternative hypotheses: the rare-mutation hypothesis and the historical contingency hypothesis. As the name suggests, under the rare-mutation hypothesis a new trait arises as a direct result of a rare mutation. In that case the probability of acquiring the new trait remains constant over time. Under historical contingency a new trait is contingent on one or more past mutations that do not give rise to new traits by themselves but make it more likely that subsequent mutations will give rise to the new trait. In that case the probability of a new trait will start out low but rise substantial after the appearance of the “potentiating” mutation(s).


Apart from the first line :) I agree with you. My first post demonstrated this. (page 2)

My appraisal about this experiment was to point out how difficult it is to even arrive at a new trait, let alone a new species. (Defination : in biology a taxonomic group potentially capable of interbreeding)

Remember this was simply a modification (which is already known to exist in the wild) of transport through the cell wall into an already operating digestive system.

This experiment demonstrates only variation (either by historical contingency or rare mutation) and only that.
Nobody that I am aware of disagrees with this level of evolution (microevolution)

It does not demonstrate a continuing progress towards speciation.

Although generations is a more accurate way of describing the process of evolution most commentary focus on timeline,and that is why I equated the number of generation in years and in human terms.
It shows in human timelines how long a process, even a minor variation, takes.
Hence my question “How many generations it would take to develop a whole digestive tract from teeth to anus.?”

Now, however we may differ as to interpretation, one fact is clear. The variation that this experiment has shown is variation within the species. It in no way demonstrates the speciation that Darwinian theory predicts. Lenski himself acknowledges this point with a question.

Will the Cit_ and Cit_ lineages eventually become distinct species?
According to the biological species concept widely used for animals and plants, species are recognized by reproductive continuity within species and reproductive barriers leading to genetic isolation between species (67).


This is quite a fundamental point to focus on because many cite this kind of “microevolution” as evidence of “macroevolution”. There is no evidence of a continuum between these two concepts.

If I may I would like to take up on Jerry Coyne’s book in my next post shortly.

Regards

Joss
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom

Re: Experimental evidence for evolution

Postby canalon » Tue Oct 19, 2010 11:05 pm

jevg wrote:
Richard Lenski wrote: Will the Cit_ and Cit_ lineages eventually become distinct species?
According to the biological species concept widely used for animals and plants, species are recognized by reproductive continuity within species and reproductive barriers leading to genetic isolation between species (67).

This is quite a fundamental point to focus on because many cite this kind of “microevolution” as evidence of “macroevolution”. There is no evidence of a continuum between these two concepts.


I have the feeling that your quote from Lenski is not complete. Because he is a microbiologist and there is one thing that I am pretty sure ho knows, and this is that the common definition of species based on genetic isolation is quite useless when talking about bacteria. Those promiscuous bugs can take DNA from many sources without much problems. The definition of a bacterial species is quite a difficult one and that you might be interested to read that paper:
http://www.pnas.org/content/96/13/7348.long
published in 1999, so only 20000 generations, and yet enough divergence accumulating to come close to define a new species.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
User avatar
canalon
Inland Taipan
Inland Taipan
 
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm
Location: Canada

Re: Experimental evidence for evolution

Postby StevePush » Wed Oct 20, 2010 3:30 am

Joss,

It is a mistake to over-interpret the data. The experiments in the paper we are discussing were designed to distinguish between Darwinian hypotheses. These particular experiments are not a test of whether natural selection can result in speciation. It's as if I said to a YECist, the Bibical account of creation cannot be true because Exodus does not explain how God created the world.

Nevertheless, I would be concerned if the LTEE produced some data that were incompatible with Darwinian theory. If I understand your position, you are saying that, because it took more than 30,000 generations for one of the E. coli populations to display a new trait, it's not possible for evolution to have occurred during the history of the Earth. But in fact the LTEE data are compatible with Darwinian theory, for the following reasons:

1) The LTEE has been under way for about 20 years. According to evolutionary theory, life on Earth began about 4.5 billion years ago. Thus evolution has occurred over a period that is 225 million times longer than the LTEE.

2) New traits do not necessaily arise one at a time. Over evolutionary time, organisms have become more complex, with larger genomes. Multiple new traits can be evolving in the same organism simultaneously.

3) The environment of the LTEE is stable. Evolution occurs most rapidly when environments change dramatically, as has happened many times during the history of life on Earth.

4) In nature, there are factors other than mutation that contribute to genetic change: sexual reproduction and other forms of recombination, polyploidy, the incorporation of whole new genomes, as when mitochrondria became part of eukaryotic cells.

5) The field of evolutionary development has shown that even small genetic changes can result in major changes in form and function.

6) Speciation has been demonstrated in many other experiments involving bacteria, plants, and animals. (See http://www.talkorigins.org/faqs/faq-speciation.html)

Regards,

Steve
StevePush
Garter
Garter
 
Posts: 22
Joined: Tue Oct 05, 2010 6:15 am
Location: Virginia, USA

Re: Experimental evidence for evolution

Postby StevePush » Wed Oct 20, 2010 3:43 am

I have the feeling that your quote from Lenski is not complete.

Your feeling is correct, Patrick. The paper goes on to suggest experiments that could determine whether the Cit+ population is evolving into a new species.

Steve
StevePush
Garter
Garter
 
Posts: 22
Joined: Tue Oct 05, 2010 6:15 am
Location: Virginia, USA

Re: Experimental evidence for evolution

Postby jevg » Wed Oct 20, 2010 11:06 pm

Steve
Just to clarify
I was responding to the question which you probably may not have fully appreciated

My question is whether there have been any experiments conducted that provide empirical support for macroevolution. Has there been any experiments that show an organism changing to something different?

I read about the fossil record and the theory in general but my question is about experiments.

The Lenski experiment that I introduced into my answer is in my opinion what good science is all about.

The background I initially provided demonstrates that I was in no way trying to read more into the experiment. Since however it is the best experiment to test what happens to an organism under stress conditions I considered and still do consider it an appropriate experiment to provide information on the question.

On the matter of speciation it is Lenski himself who brings up this point. And my direct quote from the paper shows this.

You are quite right that Lenski probably has an understanding of the biological concept of species in bacteria that may be different from that which I defined, but the point is that whatever definition we apply Lenski himself did not consider that speciation had taken place.

It is also clear that historical contingency is a theory that provides the drive towards speciation. So this experiment is about the mechanism of speciation. After all Darwinian theory is about speciation.

And my point was, that this experiment which is probably the most extensive one yet, has not shown that speciation can occur in this manner. Will it as time goes on – well that is currently an unanswered question and therefore science as yet, using the scientific method, has not answered this question.

Therefore the Darwinian mechanism is not a proven theory and I simply argue that it should not be presented as a fact as it so often is.

Just to also clarify we are not talking about 30,000 generations. Please remember that there are 12 populations and the experiment has now proceeded past 50,000 generations for each population. That makes 600,000 generations so far.

I have read somewhere (I will look it up in a follow up) that it is considered bacteria became settled in about the first billion years.

As regards YEC’s

I have had discussions with them, and clearly they have a misunderstanding of the text they place their belief in.
Genesis 1 – 2:4 is a historical narrative and not a scientific postulate. It actually says so itself.
Here is what it says at the conclusion in Gen 2:4
“These are the generations (history) of the heavens and of the earth when they were created, in the day that the Lord God made the earth and the heavens.”

Notice the use of the word generations which means history in the original language.
Notice also the fact the day in this verse refers to all the creative days mentioned previously.
So the bible itself does not equate the word day as a 24 hour period, but yet many fundamental religionists believe it as a fact.
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom

Re: Experimental evidence for evolution

Postby StevePush » Thu Oct 21, 2010 1:36 am

Joss,

We'll just have to agree to disagree about the LTEE. I still think you're trying to extract a conclusion from that paper that is not supported by the data.

But even if the populations in the LTEE never became distinct species, that result in a single experiment would not falsify Darwinian theory. The theory does not predict that every genetic change will lead to a speciation event. But there are many studies that do document speciation events. The three web pages below provide dozens of examples:

http://www.talkorigins.org/faqs/faq-speciation.html

http://www.talkorigins.org/faqs/speciation.html

http://www.talkorigins.org/indexcc/CB/CB910.html

If you are really trying to make a fair assessment of Darwinian theory, you should weigh all of the evidence.

Steve
StevePush
Garter
Garter
 
Posts: 22
Joined: Tue Oct 05, 2010 6:15 am
Location: Virginia, USA

Re: Experimental evidence for evolution

Postby canalon » Thu Oct 21, 2010 2:38 am

jevg wrote:On the matter of speciation it is Lenski himself who brings up this point. And my direct quote from the paper shows this.

You are quite right that Lenski probably has an understanding of the biological concept of species in bacteria that may be different from that which I defined, but the point is that whatever definition we apply Lenski himself did not consider that speciation had taken place.


Your answer surprised me, so I went to look for the paper, and I am indeed surprised by the quote. The paper I linked to and that he co-authored compares the different lineages and uses some of the criteria used to define species in bacteria. It was done long ago and I would not be surprised if even more divergence had accumulated since.
But in the paper you cite Lenski is making a point that should not be ignored. in the LTEE there is little to no sex between the bacteria. That is something very different with what is observed in real life. Exchange of genetic material is probably very important, although quite hard to observe. But I have worked on said subject, and I can tell you that horizontal gene transfer in the larger environment are probably quite important.

And I must say that I find you very polite with regards to YECs.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)
User avatar
canalon
Inland Taipan
Inland Taipan
 
Posts: 3909
Joined: Thu Feb 03, 2005 2:46 pm
Location: Canada

Re: Experimental evidence for evolution

Postby jevg » Thu Oct 21, 2010 3:44 pm

Steve

I don’t know if you have actually checked the papers themselves that Chris Stassen has referenced to show speciation as he claims.
His first example is here
http://www.genetics.org/cgi/reprint/55/1/141.pdf

Now if you wish to read the entire paper and fry your brain as it has mine please go ahead :)
However may I refer you to the summary on page 14.

But before that Dobzhansky and Pavan state very clearly that they are dealing with at least 5 races within the species Drosophila pcrulistorum. This experiment was about determining the cause of sterility in one of the strains during hybridization, as I understand it. They could not establish the actual cause, however they hypothesize that it may be the result of some symbiotic relationship between Drosophilia and a virus or other microorganism. The summary below confirms this.

SUMMARY
The origin in the laboratory of a sterility of male hybrids between strains which were previously fertile is described. The strain involved is the “new Llanos,” descended from a progenitor collected in the Llanos of Colombia. This strain was giving fertile hybrids with the Orinocan incipient species of Drosophila pcrulistorum.but is now producing sterile male hybrids. In evolving the sterility, the new Llanos has not become sexually isolated from its progenitor. New Llanos males continue to be accepted by Orinocan females, and vice versa.-The population from Raposo, Colombia, shows the same relationship to the Centro- American inrinient species as the new Llanos does to the Orinocan one. Alterations of the kind which took place in the Llanos strain in the laboratory occur also in nature. The genetic properties of two other transitional strains, Marco and Santa Marta, are described.
The hypothesis is put forward that the process of speciation may be initiated by establishment of new symbiotic relationships between Drosophila and a virus or other microorganism.

(my highlights)

Now you will notice in the summary that they refer to the “new Llanos” as a strain of the species but hypothesize that the process is one of speciation.

In the Appendix that follows Costas. D. Kastritsis in his analysis – well let him explain

“The data given above suggest the following conclusions: (1 ) the Santa Marta strain is very closely related to the Centroamerican “race”. (2) the Llanos strain is chromosomally unique but related to the Orinocan “race”. and ( 3 ) the Marco strain, on the basis of chromosomal morphology, is closely related to the Transitional and Centroamerican “races”, and somewhat related to the Llanns strain”


This is an examination of hybrid sterility within the species. The “new Llanos strain is still Drosophila.
If more confirmation is needed then here is another paper.
http://www.genetics.org/cgi/reprint/69/1/63.pdf

Now I have not checked out the other examples he cites but my instinct tells me that the Fireweed still remains Fireweed, the Faeroe Island house mouse still remains a Faeroe Island house mouse and so on.

Really Chris Stassen is pushing the envelope out a bit to cite these as examples of speciation.

Joss
jevg
Death Adder
Death Adder
 
Posts: 50
Joined: Thu Jun 17, 2010 4:51 pm
Location: South Wales United Kingdom

PreviousNext

Return to Evolution

Who is online

Users browsing this forum: No registered users and 1 guest