Transitional Species

[thereal]

For those of you who are interested in evolution and the presence/absence of transitional species in support of evolution, here is a link to the recent discovery of yet another "fishopod", an organism with both fish and tetrapod characteristics:

http://news.yahoo.com/s/ap/20060406/ap_ ... N5bmNhdA--

[Canuckster1127]

For those of you who are interested in evolution and the presence/absence of transitional species in support of evolution, here is a link to the recent discovery of yet another "fishopod", an organism with both fish and tetrapod characteristics:

http://news.yahoo.com/s/ap/20060406/ap_ ... N5bmNhdA--

Saw this on the train into work this morning.

Pretty intersting stuff! Good to see some restraint in the article too not overstating the implications.

Still, a very important find!

[August]

More smokescreens and handwaving from the evolutionary community, although the mainstream press of this has also been way overblown.

One of the scientists (Jennifer Clack) had this conclusion:

It's impossible to tell if Tiktaalik was a direct ancestor of land vertebrates, she said, but if a scientist set out to design a plausible candidate, "you'd probably come up with something like this."

It is being sold as a "transitional species", but it is impossible to tell if it was an ancestor to the species being transitioned to?

[Canuckster1127]

More smokescreens and handwaving from the evolutionary community, although the mainstream press of this has also been way overblown.

One of the scientists (Jennifer Clack) had this conclusion:

It's impossible to tell if Tiktaalik was a direct ancestor of land vertebrates, she said, but if a scientist set out to design a plausible candidate, "you'd probably come up with something like this."

It is being sold as a "transitional species", but it is impossible to tell if it was an ancestor to the species being transitioned to?

What would you describe it as?

I agree there's always a call for caution.

However, in fairness, criticism of evolution has centered very much on the lack of transitional species and here we have something that fits the bill and fills a previous gap.

Caution is needed and there's always a tendency to overstate the importance of something when it is being revealed. Wishful thinking kicks in.

But by the same token, just because some may not like the implications, that requires at least some plausible positive explanation for the fossil and its significance.

This may illustrate the danger of relying too heavily on an argument from a lack of evidence. The evidence may not be exactly what anyone expects it to be, but when it shows up, you better be prepared to deal with it and not just try and discredit it it, because you may not like what it infers.

Not saying you are necessarily doing that .... but it does raise the opportunity to make the observation.

[BGoodForGoodSake]

One of the scientists (Jennifer Clack) had this conclusion:

It's impossible to tell if Tiktaalik was a direct ancestor of land vertebrates, she said, but if a scientist set out to design a plausible candidate, "you'd probably come up with something like this."

It is being sold as a "transitional species", but it is impossible to tell if it was an ancestor to the species being transitioned to?

There is a pragmatic reason behind this statement.
It is possible for there to have been many different species which arose from a common ancestor. Not all of them would have been the ancestor of amphibians.

These creatures could have been geographically distributed leading to many separate populations. This particular find may not have belonged to the population which gave rise to amphibians.

A good analogy is a brick furnace.
Bricks are formed and put into lots.
But not all of the bricks are destined to go into single family homes.
If this place closed down many years ago and a child finds one of these bricks, he could say that it was one of these bricks which went into building the home he lives in. But he cannot say for sure that the brick he found was allotted to this particular use.

[August]

More smokescreens and handwaving from the evolutionary community, although the mainstream press of this has also been way overblown.

One of the scientists (Jennifer Clack) had this conclusion:

It's impossible to tell if Tiktaalik was a direct ancestor of land vertebrates, she said, but if a scientist set out to design a plausible candidate, "you'd probably come up with something like this."

It is being sold as a "transitional species", but it is impossible to tell if it was an ancestor to the species being transitioned to?

What would you describe it as?

I agree there's always a call for caution.

However, in fairness, criticism of evolution has centered very much on the lack of transitional species and here we have something that fits the bill and fills a previous gap.

Caution is needed and there's always a tendency to overstate the importance of something when it is being revealed. Wishful thinking kicks in.

But by the same token, just because some may not like the implications, that requires at least some plausible positive explanation for the fossil and its significance.

This may illustrate the danger of relying too heavily on an argument from a lack of evidence. The evidence may not be exactly what anyone expects it to be, but when it shows up, you better be prepared to deal with it and not just try and discredit it it, because you may not like what it infers.

Not saying you are necessarily doing that .... but it does raise the opportunity to make the observation.

If you have followed other similar discussions here, you would have noted that the unanswered question regarding using fossil evidence as proof for evolution is how the fossil lineage can be falsified. The arbitrary insertion of one fossil between others to generate an imaginary lineage is based on the wishful thinking of those who do it.

The discovery of this fossil shows that there once was a species such as this, and is consistent with the prediction that ~99% of all life that once lived on earth is extinct, and ~90% is undiscovered. Hopefully we will continue to discover more.

Have you read the actual scientific articles about the discovery? It is a lot more cautious in tone than the mainstream press articles, and in fact, while there is speculation that this may a be a transitional form, there is also speculation to the contrary. For example:

Although these small distal bones bear some resemblance to tetrapod digits in terms of their function and range of movement, they are still very much components of a fin. There remains a large morphological gap between them and digits as seen in, for example, Acanthostega: if the digits evolved from these distal bones, the process must have involved considerable developmental repatterning. The implication is that function changed in advance of morphology.

Of course, there are still major gaps in the fossil record. In particular we have almost no information about the step between Tiktaalik and the earliest tetrapods, when the anatomy underwent the most drastic changes, or about what happened in the following Early Carboniferous period, after the end of the Devonian, when tetrapods became fully terrestrial. But there are still large areas of unexplored Late Devonian and Early Carboniferous deposits in the world — the discovery of Tiktaalik gives hope of equally ground-breaking finds to come.

But if this is truly a transitional form, where is the direct ancestoral line and descendants? Where is the record of mutations that lead to the transition? What was the status of this specimens breathing, locomotion and hearing, compared to either fish or land-dwellers? What evidence is there that the biomechanics, genetic development and skeletal structure developed into a transition from water to land? What caused the mutations, and how did that affect other creatures in the same environment? Why has this not been observed in reverse, where land-dwellers have fully evolved into water creatures?

Similar claims were made before, about the Panderichthys. That was the previous version of the missing link...

[Canuckster1127]

OK. Fair enough.

But it obviously is more than we had before and is in keeping with the type of transitions expected.

Minimizing its impact can be taken too far as well.

It's ironic in one sense to see an argument where the absence of transition forms, forms the basis of minimizing and rejecting a theory and then that self-same argument is used to appeal against any such forms as they are discovered as too few of those that must be missing to mean anything.

I think we need to be a little more fair in our process and do more than just attempt to diminish these types of discoveries.

[August]

I think we need to be a little more fair in our process and do more than just attempt to diminish these types of discoveries.

I'm not trying to diminish the discovery, I am pointing out that the conclusions are based on false premises. I am equally as excited to see discoveries of this type, I just don't buy that it is further support for a flawed theory.

But it obviously is more than we had before and is in keeping with the type of transitions expected.

Maybe you can point to where all of these expectations are listed, so that we can check them off as discoveries are made? It seems to me that we always get the comment that "this is what was expected" after the fact. I have not personally ever seen an exact prediction of what we should expect in the fossil record, only such generalizations that almost anything can fit.

It's ironic in one sense to see an argument where the absence of transition forms, forms the basis of minimizing and rejecting a theory and then that self-same argument is used to appeal against any such forms as they are discovered as too few of those that must be missing to mean anything.

Darwin himself predicted millions of transitional forms. There is a distinct lack of transitional forms to the extent that he predicted. And if evolution is such a well-proven fact as it is made out to be, why is this discovery so important? We should be swimming in transitional forms, instead, there are so few that even the scientist who discovered this one says it is impossible to know where this fits, i.e. no ancestor or descendant, but we should assume it does.

[Canuckster1127]

I think we need to be a little more fair in our process and do more than just attempt to diminish these types of discoveries.

I'm not trying to diminish the discovery, I am pointing out that the conclusions are based on false premises. I am equally as excited to see discoveries of this type, I just don't buy that it is further support for a flawed theory.

But it obviously is more than we had before and is in keeping with the type of transitions expected.

Maybe you can point to where all of these expectations are listed, so that we can check them off as discoveries are made? It seems to me that we always get the comment that "this is what was expected" after the fact. I have not personally ever seen an exact prediction of what we should expect in the fossil record, only such generalizations that almost anything can fit.

It's ironic in one sense to see an argument where the absence of transition forms, forms the basis of minimizing and rejecting a theory and then that self-same argument is used to appeal against any such forms as they are discovered as too few of those that must be missing to mean anything.

Darwin himself predicted millions of transitional forms. There is a distinct lack of transitional forms to the extent that he predicted. And if evolution is such a well-proven fact as it is made out to be, why is this discovery so important? We should be swimming in transitional forms, instead, there are so few that even the scientist who discovered this one says it is impossible to know where this fits, i.e. no ancestor or descendant, but we should assume it does.

I'm not arguing that this is definitive. As you know from other threads, I am not an evolutionist. I'm not anti-evolution per se as a possible mechanism of God's creative process, but I don't believe that sufficient evidence exists to extrapolate it to the extent done by many.

In fairness, while your appeal to Darwin is correct as far as it goes, I think Darwin's speculations don't strongly represent the theory as it has developed. Punctuated Equilibrium comes to mind on the Evolutionist side, as does progressive creationism on the other.

I think it is a very interesting discovery and providing, as it does elements of both land dwelling and sea dwelling life, it is fair game to speculation in all camps. Speculation is not fact however and I appreciate the other elements you've added.

[BGoodForGoodSake]

But it obviously is more than we had before and is in keeping with the type of transitions expected.

Maybe you can point to where all of these expectations are listed, so that we can check them off as discoveries are made? It seems to me that we always get the comment that "this is what was expected" after the fact. I have not personally ever seen an exact prediction of what we should expect in the fossil record, only such generalizations that almost anything can fit.

Here's a more detailed account.
http://www.nature.com/news/2006/060403/ ... 403-7.html

Fish that may have been beginning to 'walk' in shallow water have been found from about 385 million years ago, and fish with limbs that bear digits have been seen from more than 365 million years ago.

The transition from lobed fin fish to those with digits was missing.

380 Million Years Ago
Eusthenopteron was a lobed fin fish. Meaning the bones and muscles which operate the fin are located outside the body as opposed to ray finned fish which have these features on the inside.


365 million years ago
Acanthostega had gills a tail fin, a lateral line, ulna shorter than radius, and eight digits on each hand.

Daeschler and Shubin set off to find this missing link in the evolutionary chain back in 1999. The pair targeted Ellesmere Island after noticing that it was listed in an undergraduate textbook as exposed Devonian rock that had not previously been explored for vertebrate fossils.

Questions reagrding the evolution of the ear structure may also be addressed with the new finding.
The transition found in this fossil is the development of independant movement of shoulder and head.

[Canuckster1127]

http://tiktaalik.uchicago.edu/index.html

Another good site with pretty clear information about the findings, and the expedition.

[August]

Sure looks like a good fossil, pretty complete front half. Has anyone seen an extensive list of characteristics unique to this particular specimen? I saw your note about the spine and head, Bgood. What else is there that is not found in other tetrapods?

[BGoodForGoodSake]

Sure looks like a good fossil, pretty complete front half. Has anyone seen an extensive list of characteristics unique to this particular specimen? I saw your note about the spine and head, Bgood. What else is there that is not found in other tetrapods?

Actually the head being able to move independant of the spine is a tetrapod feature.

Other Tetrapod features include a flattened head and expanded ribs.

Fishlike features include, scales, fins and most likely gills.

[August]

Right, but how is this different from other tetrapods?

[BGoodForGoodSake]

Right, but how is this different from other tetrapods?

Tiktaalik was not a tetrapod. It has fins and fishlike jaws. It probably did not posess vertebrae but a primitive notochord like structure. Because of this it could not have lived primarily on land.

The transition from water to land requires a change in the spine. On land a fishes spine will bend on its own weight.

Necks are required for terrestrial life. In the water a fish can orient its entire body in the desired direction. In contrast terrestrial movement is confined to the surface of the ground.