Transitional forms in the fossil record

[laptoppop]

One major problem I have with the fossil record is the lack of transitionary forms. This may be due to a lack of understanding on my part - so lets start talking about it.

As I understand it - some mechanism (mutation?) produces a variation in the characteristics of a population. This variation is then worked on by natural selection which causes the more beneficial trait within a given enviornment to have greater and greater number of individuals with the beneficial trait within the population. This is then repeated over and over and over and over (millions of times?) to produce the complex variety of life we know of today.

This would lead me to expect a fossil record with lots of populations with multiple characteristics in progress. Instead, it seems like the record is quantized - that for the most part it consists of life which is at discrete steps - adapted for a particular ecological niche.

For example - the trilobite eye. It has been postulated that this developed a bit at a time, into the amazingly complex structure that eventually was fossilized. However, what we see is fully developed eye -- no development -- no mixed populations some with light sensitive spot, others with eye, etc.

How would one reconcile the expectations with the actual record? What's wrong with my expectations? It seems like the structures require huge number of simultaneous mutations/additions/modifications to the genetic code to show up as they do -- and then the secondary populations are supposedly reduced with such rapidity that there are no secondary traits left to be fossilized.

If evolution were true, shouldn't we see much much much more of a continuum of life?

 

[random_guy]

One thing before we begin, do you know what the scientific definition of transitional fossil is? If not, give a definition. The problem is whever there is a debate about transitional fossils Creationists tend to use the non-scientific definition which renders the entire argument pointless.

 

[random_guy]

One thing before we begin, do you know what the scientific definition of transitional fossil is? If not, give a definition. The problem is whever there is a debate about transitional fossils Creationists tend to use the non-scientific definition which renders the entire argument pointless.

 

[rmwilliamsll]

f evolution were true, shouldn't we see much much much more of a continuum of life?


it is a big issue. start out small and easy analogies and see where they can lead.

i live in the Southwest US. Now pretend you could dig up all of the human bodies, say within 10 miles of where i live. You would know exactly when they were buried and have no timing problems.

take just one measurement. overall height, length of leg bone or arm bone, you choose.

what would you find?

why would you not find a continuum from say 1000CE to today? why is there a steady increase for the last 100 years? what does this discontinuity in the late 18thC mean? why did the average height increase so much? and again in the late 19thC another huge jump, why?

solve these questions.
using only the bones, no real knowledge of the history etc of the area. just the measurements.

now throw out all the skeletons except parts of two.
you do not have an exact date for these, they are incomplete. now reconstruct the thinking you used to answer the questions above.

can you do it?

now, say i tell you that i live in Tucson AZ? you can get a history of the area and repeat the process, would you come to a different set of conclusion?

now point out the transitional fossils between the smaller human and the larger human?
surprise, there aren't any. not around here, maybe not anywhere. why?

this is a good analogy for what happens in the fossil record.

 

[philadiddle]

here's from talk origins, sorry for taking the lazy way out.
http://www.talkorigins.org/faqs/faq-transitional.html

http://www.talkorigins.org/faqs/comdesc/section1.html#morphological_intermediates

 

[gluadys]

One major problem I have with the fossil record is the lack of transitionary forms. This may be due to a lack of understanding on my part - so lets start talking about it.

As noted, you need to start with the proper definition of "transitional".

This variation is then worked on by natural selection which causes the more beneficial trait within a given enviornment to have greater and greater number of individuals with the beneficial trait within the population.

Can you describe what you mean by "worked on"? What is it that causes a larger and larger proportion of individuals to exhibit the new trait? I think a proper understanding of natural selection is key to understanding evolution and speciation.

This would lead me to expect a fossil record with lots of populations with multiple characteristics in progress. Instead, it seems like the record is quantized - that for the most part it consists of life which is at discrete steps - adapted for a particular ecological niche.

Remember how selective the fossil record is. It is as if there was once a complete film of every step of a trip across the U.S., but major bits of it have been lost and all we have now are a few isolated frames with which to reconstruct the journey. One estimate I saw was that of all species that have ever existed less than 1% were ever fossilized. Then of all species fossilized less than 1% have not been destroyed in subsequent geological events. And of the fossils that still exist, less than 1% are accessible and of these less than 1% have actually been found. I have no idea how accurate these estimates are, but it gives an idea of why the fossil record is not, and never has been, the backbone of evidence for evolution. Dawkins has gone as far as saying we have enough evidence for evolution without any fossil record at all.

On the other hand, unless it was the last generation prior to extinction, every fossil is, in principle, a transitional fossil.

For example - the trilobite eye. It has been postulated that this developed a bit at a time, into the amazingly complex structure that eventually was fossilized. However, what we see is fully developed eye -- no development -- no mixed populations some with light sensitive spot, others with eye, etc.

An excellent resource on this particular problem is In the Blink of an Eye by Andrew Parker which outlines his "Light Switch Theory" in regard to the Cambrian Explosion. There is development and increasing evidence of development among the ancestors of the trilobites. It is discussed in this book.

How would one reconcile the expectations with the actual record? What's wrong with my expectations? It seems like the structures require huge number of simultaneous mutations/additions/modifications to the genetic code to show up as they do -- and then the secondary populations are supposedly reduced with such rapidity that there are no secondary traits left to be fossilized.

No, it does not require simultaneous mutations or modifications. This is one of the key creationist misunderstandings of evolution and transitions. Just because no precursors have turned up in the fossil record yet does not mean all the intermediate modifications occurred simultaneously. It just means intermediates either were not fossilized at all, or that they haven't yet been discovered. Now that we are finding more and more complex life forms in pre-Cambrian formations, several lines of development that were once theory now have fossil support.

This has been the repeated story of many once "unbridgeable" gaps in the fossil record and we can expect more of the same in times to come.