DNA evidence and fossil record

[zoegirl]

When I was doing some research in to the horse question from the Spalding thread, I ran across this article from 2005. It brings up the startling conclusions that many of the horse fossils, when their mitochondrial DNA was examined, are representing the same species of horse. Kind of shakes up their phylogenetic trees AND places the fossil record on shaky grounds. Many of the evolutionary relationships are still based on physical differences of the fossils. THe horse fossil record has always been one of the favorite icons of evolutionists proudly proclaiming the abundant transitional fossils throughout the evolutionary history of the horse, and yet here they are saying that they will have to rethink their phylogenetic trees. AT THE VERY LEAST, this is grounds for approaching the fossil tree with caution. I have always told my students that the weakest part of the fossil record is that we have no real way of knowing which fossils represent different species. (look at the skeletons of the various breeds of dogs!) Actually found at one time a scientific paper admitting that they would consider all of the different breeds of dogs different species if they had found the skulls. I've since lost the reference (so annoyed at myself!)

Just a sample

A final analysis of horse specimens from the Pleistocene, historic, and recent caballines—which have been grouped as separate species based on their diverse size—suggests that all North American caballines may belong to the same species. Altogether, the results suggest that just two horse lineages—caballine and stilt-legged—may have lived in North America during the Late Pleistocene. Both lineages showed regional and temporal variations in size and form. Though these variations have been taken to represent many different species, the authors propose that the two lineages are more likely just two species whose variations reflect adaptations to different environments. If true, this model could provide a tool for exploring how environmental adaptations give rise to morphological variation.

http://www.pubmedcentral.nih.gov/articl ... id=1159167

Any thoughts? Just to clarify my position...Old earth creation...no doubt that the fossils exist or denying their age or existence...simply their relationships with other fossils and their significance with macroevolution

[zoegirl]

Here is another link to the dog skull example

http://lancelet.blogspot.com/2005/12/sp ... -i_07.html

My problem with his explanation is that evolutionists clearly DO use these morphological differences to describe evolutionary trees. Maybe not for cladograms, but for supporting transitional fossils, historical events, well, pretty much everything.

So, thinking that this article on the horse is pretty groundbreaking, inasmuch as it essentially states that all of the previous assumptions on morphology is not as ironclad as they thought. Would love to see this done on the Galapagos finches.

[BGoodForGoodSake]

I was going to post yesterday but your second post covers all my points.


One additional thing to note is that the cladistics are based on modern animal groups.
In other words fossils are arranged in relation to modern flora and fauna.

That is why Cambrian organisms fall into crown groups(phyla).

If there were biologists on the Earth during the Cambrian, the cladistics would be based on Cambrian organisms. And they would all belong within a single clade.

This fact is often misunderstood.

[zoegirl]

No, I agree with you in principle and have no problems with the cladistics; however.... this really wasn't my point. Ultimatley cladistics say that we evolved from a common ancestor with chimps, BUT HOW we evolved from this common ancestor is what I feel is the issue.

When it comes to supporting the evolutionary history, EVERY textbook out there has these great figures and diagrams concerning the evolutionary descent of humans, horses, perhaps whales. They boast of the vast morphological differences that lead them to these great evolutionary trees. Believe me, having taught for 14 years, I am very familiar with what thay say., And without fail, every textbook points to these morphological differences as the basis for making these lovely drwaings showing new species. Just look at the branching in the famous horse evolution. Yet now they have to redraw these trees (and the interesting question will be how long it will take before this is corrected) with, in their words, much puning needed.


My point is that what they have always assumed to be true concering descent and speciation IN THE PAst may not actually be true. Rather significant in what they now have to re-examine. Also changes the assumed speciation events in the past, also significant because this is always used to support the idea in the present. Also significant because it now means that every evolutionary descent theory must now use the DNA evidence and I simply will be fascinated with what this will bring out.


Simply shakes things up a little I hope that this is the direction of a lot of the research.

[pete]

hi there, I'm new here but zoegirl's comment about galapogos finches interested me. I did a quick search for "darwin finch DNA" on google and found an article the phylogeny of Darwin finches. Reference is Sato et. al 1999, proceedings of national academ of sciences vol 6 pages 5101 - 5106. This study was based on mitochondrial DNA, and seems to confirm the speciation based on morphological attributes. It's not the only study and a short article entitled a new perspective on the evolutionary history of darwin's finches mentions a lot of the studies of the galapagos finches."http://findarticles.com/p/articles/mi_q ... i_n9136869

although the article by weinstock et al about fossil horses calls phylogenies based on morphological attributes into question it does not mean that the current evolutional history of all species is incorrect


peace out

[zoegirl]

hi there, I'm new here but zoegirl's comment about galapogos finches interested me. I did a quick search for "darwin finch DNA" on google and found an article the phylogeny of Darwin finches. Reference is Sato et. al 1999, proceedings of national academ of sciences vol 6 pages 5101 - 5106. This study was based on mitochondrial DNA, and seems to confirm the speciation based on morphological attributes. It's not the only study and a short article entitled a new perspective on the evolutionary history of darwin's finches mentions a lot of the studies of the galapagos finches."http://findarticles.com/p/articles/mi_q ... i_n9136869

although the article by weinstock et al about fossil horses calls phylogenies based on morphological attributes into question it does not mean that the current evolutional history of all species is incorrect


peace out

I know that it doesn't destroy the entire fossil record.

I'm good with that...thanks for referencing the article. I will try to get time to read it. I think my interest is that it just provokes more study and leads to more questions. Always good.

I know that some of the species of the finches can still interbreed. I'd like to read that to see more information.

[Forum Monk]

... the Stone Age mind which evolved over the last several hundred thousand years was perhaps more selective about mixing their genes with outsiders.

Or perhaps not so selective. There is growing support for the idea that HSN did NOT go extinct from famine, disease, or warfare; but rather, he was basically "absorbed" into the HSS stream through interbreeding. In spite of the obvious morphological differences, vestiges of his physical characteristics are present in HSS. DNA studies at this point are inconclusive and controversial.

[Forum Monk]

The conclusions are obviously debated and the evidence very preliminary. As you have discovered, Trinkhaus is one of the leading proponents of the idea and clearly much of what we thought we knew about HSN has been turned upside-dwon by recent discoveries. Here are few articles to get everyone's feet wet but at present wet feet are about as far one can go. True, the mtDNA studies are opposed to the notion. But the fossils and archaeological studies are very interesting.

http://news.nationalgeographic.com/news ... thals.html

Recently the fossil was radiocarbon dated to 33,000 years ago and thoroughly examined, revealing the controversial anatomical feature.

The otherwise human skull has a groove at the base of the back of the skull, just above the neck muscle, that is ubiquitous in Neandertal specimens but has never been seen in the remains of a modern human, argues study leader Erik Trinkaus, an anthropologist at Washington University in St. Louis, Missouri.

John Hawks commentary on the above article:
http://johnhawks.net/weblog/reviews/ear ... _2007.html

Anyway, more on early humans in Europe later. The article ends with an interview with Eric Delson, who is not dismissive but not convinced, either. The final paragraph has this priceless quote:

"But the genetic evidence is not in favor of hybridization, and this fossil does not convince me, nor do the several from Central Europe. I am still waiting for a 'smoking gun,' or perhaps in this case 'a bleeding hand axe.'"
Hmmm....that seems a little like demanding a sign from beyond. I grant, a suprainiac fossa is not exactly stigmata, but hey, a bump here and groove there, and pretty soon you're talking real interbreeding!

John Hawks again, on DNA tests conducted on a recent find which was either contaminated or hybrid:
http://johnhawks.net/weblog/reviews/nea ... ?seemore=y

Are we discovering the human equivalent of mules? Perhaps, but the original point - man is not now nor aparently never was very selective about his breeding urges.

[Forum Monk]

huh?
Looks like "an ape" grew wings and flew away. His posts are deleted.

[Kurieuo]

huh?
Looks like "an ape" grew wings and flew away. His posts are deleted.

He/she was using a false email account (another person's who was complaining) and so was deleted.