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Author Topic:   Plausible Evolutionary Chains for Educational Use
Equinox
Member (Idle past 5141 days)
Posts: 329
From: Michigan
Joined: 08-18-2006


Message 1 of 25 (374019)
01-03-2007 1:30 PM


In an earlier thread, a member asked to see a hypothetical chain (between major groups, like class or order) consistent with the fossil record. In other words, drawings of creatures from a fish (say, a lobe finned fish) through intermediates like Tiktaalik, and Ichthyostega, through an amphibian, to say an early reptile like Dimetrodon. It only has to be plausible (consistent with the fossil record)- not that we have to know for sure exactly that this is the actual descendant.
With such a question, we should have provided a ton of very useful and clear pictures. I find it embarrassing as a scientist, educator, and evolution supporter that we don't have these on the sides of buses, not to mention available in discussion here.
This is not a thread for talking about how we can’t know exact ancestry (which isn’t needed in this case anyway), nor about how evolution produces trees or bushes (which is irrelevant, since a chain will still exist behind each organism that has ever lived, all the way from a redwood to it's gggggreat grandfather bacterium).
Instead, this is a thread for discussing and even finding/making good chains. Also (as a person with the computer skills of a Neanderthal), I'd like to find out what we can do to make these generally accessible. I also am very busy, so I'll contribute and help as I can.
Some for starters:
1. There is a video version on the Cosmos series. I'll find out which episode.
2. The whale series on post #54 here http://EvC Forum: evolutionary chain -->EvC Forum: evolutionary chain.
3. Hominids 29+ Evidences for Macroevolution: Part 1 (also, jaw series there is good).
4. fish to mammal (Jaw/Ear focus) (page down to where it says "inner ear bones" http://www-rohan.sdsu.edu/...iller/chordates2/Chordates2.htm
5. Horse feet: Bpeah.com is for sale | HugeDomains
6. Another video version is in the movie "Mission to Mars", though someone could do a lot better if they wanted to.
7. Another video version is that Bud commercial that was shown only in Europe and not in the US due to worries about fundy reactions to evolution. Again, someone could do a lot better (and more accurately).
RAZD, thanks for suggesting this start. I didn't attach the pictures since I didn't see copyright permssion, but did provide links above. (Mods, feel free to insert pictures if we have copyright permission or whatever we need).
What is our next step to get a bunch of these, especially detailed ones showing many steps (even without fossils for all of them), and make them accessible? Maybe some kind of wiki format? Hosted where? Is there already one that I don't know about?
Which forum? Maybe Biological Evolution?
Thanks all-
Edited by Equinox, : Added suggested forum.

-Equinox
_ _ _ ___ _ _ _
You know, it's probably already answered at An Index to Creationist Claims...
(Equinox is a Naturalistic Pagan -  Naturalistic Paganism Home)

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AdminAsgara
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Message 2 of 25 (374024)
01-03-2007 1:40 PM


Thread moved here from the Proposed New Topics forum.

  
RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 3 of 25 (374291)
01-04-2007 12:10 AM
Reply to: Message 1 by Equinox
01-03-2007 1:30 PM


Good start. I can think of a couple of other examples, but tonight is too late to pull them up here (maybe tommorrow).
It may also be difficult to keep this from being bombarded by discussion of the different chains (and the "gaps" in our knowledge) rather than the issue of providing them.

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 4 of 25 (374788)
01-05-2007 7:16 PM
Reply to: Message 1 by Equinox
01-03-2007 1:30 PM


First Chain - Forams and Transitions
I think the place to start this is with the foraminifera information from Arnold and Parker. This is important for several reasons: it demonstrates speciation - "micro"evolution - over an extended period of time - not just natural selection (peppered moths and galapogos finches) - nor is it "macro"evolution (with the development of significant new features, and the issue of what is "significant" left undefined), and it also shows that the change over time is continuous (albeit at changeable rates) and there is no "stasis" observed in any species.
It will also bring out two main problems that creationists generally have: the age of the earth and the world wide flood mixing of sediments. These are issues that creationists need to address in order to deal with the issue of evolution on a rational level: if they cannot develop some practical physically possible scenario that makes this evidence compatible with either of these concepts then they need to consider that the concepts are wrong.

First, what are forams?

From Ref (1):
quote:
The Foraminifera, or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net. They typically produce a shell, or test, which can have either one or multiple chambers, some becoming quite elaborate in structure. ... They are usually less than 1 mm in size, but some are much larger, and the largest recorded specimen reached 19 cm.
The form and composition of the test is the primary means by which forams are identified and classified. Most have calcareous tests, composed of calcium carbonate. In other forams the test may be composed of organic material, made from small pieces of sediment cemented together (agglutinated), and in one genus of silica. Openings in the test, including those that allow cytoplasm to flow between chambers, are called apertures.
Tests are known as fossils as far back as the Cambrian period, and many marine sediments are composed primarily of them. For instance, the limestone that makes up the pyramids of Egypt is composed almost entirely of nummulitic benthic foraminifera. Forams may also make a significant contribution to the overall deposition of calcium carbonate in coral reefs.

(Phase-contrast photomicrograph by Scott Fay, UC Berkeley, 2005. Image copied from wikipedia to save bandwidth. This image is licensed under the Creative Commons Attribution ShareAlike License v. 2.5: )
The image above shows the protoplasm covered test (shell) and several pseudopods of a living species of foraminifera. Fossil species would be similar, with different shape shells and different numbers of pseudopods (limited by the number of holes in the shells).
Also: http://www.eforams.icsr.agh.edu.pl/index.php/TAXONOMY
- DOMAIN: Eukaryota (Whittaker & Margulis, 1978)
- KINGDOM: Protista (Haeckel, 1866 ..... See Phylogeny of Protista)
- PHYLUM: Granoloreticulosa
- ORDER: Foraminiferida (Eichwald, 1830)
Forams are an 'order' in the macro-taxonomic classifications system, with 'suborders', 'superfamilies' and 'families' before we get down to the species level discussed below (we need not be concerned with the levels of taxonomy at this point in the debate, this is just for information).

The Fossil Record

from Ref (2):
quote:
In recent years, however, scientists began revisiting the oceans, ... Some intriguing results turned up recently in the laboratories of two Florida State University (FSU) marine paleontologists.
Tony Arnold and Bill Parker compiled what may be the largest, most complete set of data on the evolutionary history of any group of organisms, marine or otherwise. The two scientists amassed something that their land-based colleagues only dreamed about: An intact fossil record with no missing links.
"It's all here--a virtually complete evolutionary record," says Arnold. "There are other good examples, but this is by far the best. We're seeing the whole picture of how this group of organisms has changed throughout most of its existence on Earth."
But it's the planktonic variety that chiefly interests Parker and Arnold. Unlike their oversized cousins, free-swimming forams are found almost everywhere in the oceans. Their fossilized skeletons, in fact, were among some of the first biological material recovered from deep ocean bottoms by scientists in the 1850s. For nearly a century, geologists have used the tiny fossils to help establish the age of sediments and to gain insight into prehistoric climates.
Only since the 1960s, though, have scientists begun to fully appreciate fossil forams' potential as a tool for use in evolutionary studies and a host of Earth sciences as well. Advanced deep-sea drilling techniques, combined with computer-assisted analytical tools, have ushered in a whole new vista of foram research. Arnold and Parker are among the first scientists to harness sophisticated technology to a foram project for the express purpose of studying evolution.
As he speaks, Arnold shows a series of microphotographs, depicting the evolutionary change wrought on a single foram species. "This is the same organism, as it existed through 500,000 years," he says. "We've got hundreds of examples like this, complete life and evolutionary histories for dozens of species."

(Image copied from ref (2) to save bandwidth. This same image also appears on ref (4).)
About 330 species of living and extinct planktonic forams have been classified so far. After thorough examinations of marine sediments collected from around the world, micropaleontologists now suspect these are just about all the free-floating forams that ever existed.
The species collection also is exceptionally well-preserved, which accounts largely for the excitement shared by Parker and Arnold. "Most fossils, particularly those of the vertebrates, are fragmented--just odds and ends," says Parker. "But these fossils are almost perfectly preserved, despite being millions of years old."
By being so small, the fossil shells escaped nature's grinding and crushing forces, which over the eons have in fact destroyed most evidence of life on Earth. The extraordinary condition of the shells permits the paleontologists to study in detail not only how a whole species develops, but how individual animals develop from birth to adulthood.
What we have essentially is a jig-saw puzzle with all but maybe 2 or 3 pieces, the whole picture is evident, and where there are a few gaps, these are surrounded by other data that help complete the picture.
This picture shows a continual process of change in species over time, fully realized and documented microevolution, with no reappearance of archaic types in modern species, no "backing and filling" as we see with Peppered Moths and Galapagos Finches, because speciation has occurred, and change moves on to new mutations and new selections of those mutations.
We see significant change in the shape of the shell of one species as it evolves over a period of 6.5 million years.

Conclusions

Several conclusions are readily apparent from this information that apply directly to the issue of microevolution:
  • Microevolution has occurred.
  • Microevolution has been documented over several successive generations of species, and not for just one speciation event.
  • Microevolution is therefore a fact in this fossil record.
  • Because further speciation occurs, microevolution does not limit subsequent changes once speciation has occurred (beyond what can occur through mutation and natural selection of the then existing species - more microevolution).
But that's not all we can glean from this example of microevolution.

Other information

Other facts from Ref (1):
quote:
Because of their diversity, abundance, and complex morphology, fossil foraminiferal assemblages are useful for biostratigraphy, and can accurately give relative dates to rocks. The oil industry relies heavily on microfossils such as forams to find potential oil deposits.
The foraminiferan life-cycle involves an alternation between haploid and diploid generations, although they are mostly similar in form. The haploid or gamont initially has a single nucleus, and divides to produce numerous gametes, which typically have two flagella. The diploid or schizont is multinucleate, and after meiosis fragments to produce new gamonts. Multiple rounds of asexual reproduction between sexual generations is not uncommon in benthic forms.
Forams are used to relatively date marine sedimentary layers due to the distinct morphological differences of the different species.
Also see Ref (5) for more information on relative dating with forams.
Forams reproduce by both sexual and asexual means.
Other facts from Ref (2):
quote:
Through dating analysis, he and his colleague showed that the forams could produce a whole new species in as little as 200,000 years--speedy by Darwinian standards. "But as fast as this is, it's still far too slow to be classed as punctuational," says Arnold.
It may be in what the foram record suggests about how life copes with mass annihilation that eventually draws the most attention to the FSU paleontologists' work. The geologic record has been prominently scarred by a series of global cataclysims of unknown, yet hotly debated, origin. Each event, whether rapid or slow, wreaked wholesale carnage on Earth's ecology, wiping out countless species that had taken millions of years to produce. Biologists have always wondered how life bounces back after such sweeping devastation.
One of the last great extinctions occurred roughly 66 million years ago and, according to one popular theory, it resulted from Earth's receiving a direct hit from a large asteroid. Whatever the cause, the event proved to be the dinosaurs' coup de grace, and so wiped out a good portion of the marine life--including almost all species of planktonic forams.
The ancient record of foram evolution reveals that the story of recovery after extinction is indeed busy and colorful. "What we've found suggests that the rate of speciation increases dramatically in a biological vacuum," says Parker. "After the Cretaceous extinction, the few surviving foram species rapidly evolved into new species, and for the first time we're able to see just how this happens, and how fast."
As the available niches fill up with these new creatures, the speciation rates slow down, and the pressure from competition between species appears to bear down in earnest. The extinction rate then rises accordingly. This scenario, says Arnold, suggests that the speciation process is sensitive to how fully packed the biosphere is with other species, not the number of individuals.
The shortest observed time interval for speciation was 200,000 years.
The rate of speciation was observed to increase after a major extinction event as there was less natural selection pressure from competition between species on new mutations in their ability to fill available ecological niches.
Other facts from Ref (3):
quote:
One of the findings already is being described -- perhaps too hastily -- as disproving Cope's Rule, so named for it's synthesis by the American paleontologist Edward Drinker Cope (1840-97). The time-honored evolutionary principle basically holds that all animal groups tend to start out small and increase in size over time.
"We've found out that apparently, lineages don't exactly work that way," Arnold said. "Many of the forams start out small, and essentially stay that way until extinction. Others do manage to wander into dramatically larger sizes, but they're the rare ones."
But the find doesn't necessarily contradict what Cope said, only what many scientists think he said, says Parker. "Cope's observation was simply that there are a few extremely large examples (of individuals) in any given lineage, and these examples always occur at the later stages of the organism's development. And that's apparently true.
"But our findings show that the vast majority of forams start small and end small, even though the mean size increases somewhat due to a few very large specimens. As you get more and more species evolving, some of them eventually manage to get moderately to very large, but most of them don't increase in size at all."
Of late, much ado has been made of the theory of punctuated equilibrium, formulated in the early 1970s by two paleontologists, Niles Eldredge and Stephen Jay Gould. New species may arise fairly quickly (over thousands instead of millions of years) from small animal populations that somehow become isolated, the theory postulates. Intermediate stages are thus too fleeting to become fixed in the fossil record.
Adherents of Darwin's theory of gradualism, in which new species slowly branch off from original stock, should be delighted by what the FSU researchers have found. The foram record clearly reveals a robust, highly branched evolutionary tree, complete with Darwin's predicted "dead ends" -- varieties that lead nowhere -- and a profusion of variability in sizes and body shapes. Moreover, transitional forms between species are readily apparent, making it relatively easy to track ancestor species to their descendants.
In short, the finding upholds Darwin's lifelong conviction that "nature does not proceed in leaps," but rather is a system perpetually growing in extreme slow-motion. This means that, in foram evolution at least, the highly touted Eldredge-Gould theory of punctuated equilibrium apparently doesn't work.
In divulging this revelation, Arnold could be forgiven for taking a modicum of perverse glee, the kind a highschool smart-aleck displays when he catches the teacher in a mistake. Gould, now among the most famous scientists in the world, directed Arnold's Harvard dissertation. But there's no room for that here, he says. Arnold maintains a warm professional relationship with his former mentor, who paid his lab a visit when FSU's Distinguished Lecture Series brought him to campus last year. Gould concedes that the forams don't fit his model of punctuated equilibrium, Arnold said.
"He was characteristically pleased to be contradicted with this information. His immediate response was that the forams are probably a special case."
The issue of punctuated equilibrium ("PunkEek") is a side issue in the evolution versus creation debate, but one that seems to reflect kinds to creationists and evolution to evolutionists. It is my opinion that this does not come into play until there is active sexual selection in a species that can select for an averaged individual type - stasis - and that until that stage is reached there should be no evidence of punkeek. That would match the evidence we see here - an organism that engages in random sexual reproduction and random asexual reproduction would not have this stasis selecting mechanism. Thus we will have to deal with this issue later if we come to evidence for punkeek.

Further Conclusions

Conclusions that bear on the debate here and further discussion of microevolution (MiE) in the next examples (yet to come):
  • The different age fossils form discrete layers in marine sediment that are identifiable around the world. These fossils all have essentially the same density, size and structure, and are generally less dense than surrounding marine sediment. These different age layers, now that Palmer and Arnold have classified the evolution of the different species of forams, are sorted by age AND evolution within the marine sediment, a fact that cannot be accomplished by any mixed water world wide flood scenario. (A WW Flood concept cannot explain this evidence.)
  • With several generations of speciation observed and the shortest observed time interval for speciation of 200,000 years, the layers of marine sediment together with the evolutionary structure of the foram fossils embedded within it, AND the evidence of the KT extinction event within the data, document an old age of the earth, much older than any YEC model can manage to accommodate. (A Young Earth concept cannot explain this evidence.)
  • Cope's "rule" was observed in some species and not in others, so it is not a universal "rule" or "law" (no real surprise there).
  • PunkEek was not observed in any of the speciation events in this fossil record, even though there was evidence of more and less rapid rates of evolution, particularly in response to the ecological vacuum created by the KT mass extinction event (at the end of the age of dinosaurs).
  • These organisms reproduce by random sexual and asexual means, and do not have an active sexual selection mechanism that could lead to stasis (and thus to the possibility of punkeek).
  • There could be other causes for PunkEek as well, that would not affect foraminifera.
I think that's enough for now.
Enjoy.


References:
(1) "Foraminifera" - wikipedia article (subject to change)
(2) "Evolution at Sea - a Complete Fossil Record from the Ocean Upholds Darwin's Gradualism Theories" adapted from an article that first appeared in Research in Review, published by Florida State University, revised Oct. 1997
(3) "The Foram Fossils: A Classic Tale of Transition - Did darwin have it right about how species evolve?" ibid, revised Oct. 1995
(4) "A Smooth Fossil Transition: Foraminifera" - with links to ref (2) and (3) by Don Lindsay, last modified: 1 December 1998
(5)"Biostratigraphic Chart of the Gulf of Mexico Offshore Region, Jurassic to Quaternary" (pdf), Witrock, R. B., A. R. Friedmann, J. J. Galluzzo, L. D. Nixon, P. J. Post, and K. M. Ross, 2003, Biostratigraphic chart of the Gulf of Publication 60, p. 155-177. American Association of Petroleum Geologists Bulletin, v. 84, p. 1905-1928. Mexico offshore region, Jurassic to Quaternary, U. S. Department of the Interior, Minerals Management Service, New Orleans.
Note: (3) and (4) contain the same basic information as reference (2) but (3) is an earlier date, and may be an online copy of the original paper.

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This message is a reply to:
 Message 1 by Equinox, posted 01-03-2007 1:30 PM Equinox has replied

Replies to this message:
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Equinox
Member (Idle past 5141 days)
Posts: 329
From: Michigan
Joined: 08-18-2006


Message 5 of 25 (376202)
01-11-2007 12:06 PM
Reply to: Message 4 by RAZD
01-05-2007 7:16 PM


Re: First Chain - Forams and Transitions
Wow, RAZD, that one’s awesome. Too bad we aren’t getting any more. The ones you mention are finely and clearly documented with fossils, which is overkill compared to the simple idea of plausible chains (where all the fossil intermediaries aren’t needed).
I think part of the lack here is because to do the drawings, one needs to be an artist, while to know what they should look like, one needs to be a serious biologist/paleontologist. Add to this that most paleontologists are specialized into a time period or type of fossil, and it gets even harder. For these, we need a team of an artist working with a paleontologist. Anybody know of a paleontologist or biologist who is interested in making some of these happen? It seems like it wouldn’t be too hard from there to find an artist who would like to do these, since I think there are more unemployed artists than there are unemployed paleontologists.
In fact, I can imagine a bunch of descent chains going from major forms of life today (for instance, a whale, a person, a snake, a horse, an ostrich, and elephant, a penguin, an octopus, or an eagle) back to prokayotes. These should be a standard part of any biology book, especially high school or below so people can get a feel for this early on.

-Equinox
_ _ _ ___ _ _ _
You know, it's probably already answered at An Index to Creationist Claims...
(Equinox is a Naturalistic Pagan -  Naturalistic Paganism Home)

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mick
Member (Idle past 4985 days)
Posts: 913
Joined: 02-17-2005


Message 6 of 25 (376440)
01-12-2007 6:33 AM
Reply to: Message 5 by Equinox
01-11-2007 12:06 PM


Re: First Chain - Forams and Transitions
Hi Equinox,
Here's a trilobite phylogeny from Paul Selden's (U Kansan) lecture notes - I think what you want to be looking at here is the number of ribs evolving along each branch.
Mick
Edited by Admin, : No reason given.

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mick
Member (Idle past 4985 days)
Posts: 913
Joined: 02-17-2005


Message 7 of 25 (376441)
01-12-2007 6:57 AM
Reply to: Message 5 by Equinox
01-11-2007 12:06 PM


Re: First Chain - Forams and Transitions
And here's one showing the necessary evolutionary modifications leading from dinosaurs to birds. Unfortunately the pictures are a bit blocky and the species aren't named - but it might be possible for somebody who knows about dinosaurs to label some of the species.
Link to source
mick
Edited by mick, : No reason given.

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 8 of 25 (376587)
01-12-2007 6:55 PM
Reply to: Message 7 by mick
01-12-2007 6:57 AM


Subtitles
Nice information - room to flesh out during further discussions.
One thing ... could you edit the subtitles to refer to each of these examples (they're not forams eh?)?
You may also want to make the images smaller with
[thumb=300](image url here)[/thumb]
you get a thumbnail image, width sized by the number (pixels), and you click on the thumbnail to see the full size
I believe it loads faster too, but percy can correct me if I'm wrong.
Edited by RAZD, : thumbnail info

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jar
Member (Idle past 393 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 9 of 25 (376592)
01-12-2007 7:01 PM
Reply to: Message 6 by mick
01-12-2007 6:33 AM


fix width too
and maybe change the width using thumb=500 for example instead of img?

Aslan is not a Tame Lion

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 10 of 25 (376612)
01-12-2007 9:15 PM
Reply to: Message 1 by Equinox
01-03-2007 1:30 PM


Fourth Chain - Horses, Feet to Hooves
People new to evolution often talk question the development of "distinctive" features, although it is sometimes difficult to pin them down on what they mean by a distinctive feature or how much change is enough.
No webpage found at provided URL: distinctively - adv.
in an identifiably distinctive manner; "the distinctively conservative district of the county"
No webpage found at provided URL: distinctly - adv.
1: clear to the mind; with distinct mental discernment; "it's distinctly possible"; "I could clearly see myself in his situation" [syn: clearly] 2: in a distinct and distinguishable manner; "the subtleties of this distinctly British occasion" 3: to a distinct degree; "urbanization in Spain is distinctly correlated with a fall in reproductive rate"
No webpage found at provided URL: dis·tinc·tive - adj.
1. Serving to identify; distinguishing: distinctive tribal tattoos. See Usage Note at distinct.
2. Characteristic or typical: “Jerusalem has a distinctive Middle East flavor” (Curtis Wilkie).
3. Linguistics. Phonemically relevant and capable of conveying a difference in meaning, as nasalization in the initial sound of mat versus bat.
We can talk about horses and the distinctive development of the modern horse and single-toe hoof from the splayed toed dog sized "eohippus":
http://www.flmnh.ufl.edu/...ci/vertpaleo/fhc/relatives10.htm (2)
quote:
Look at how the bones in horse feet have changed over time.
They became longer and more streamlined, enabling horses to run faster to avoid predators.
Check the above link to see images of the legs of four different horse ancestors. You can see a splayed toe stance for Hyracotherium and Miohippus but a single toe stance in Merychippus and Equus.
http://www.geocities.com/...rk/7841/horse_evol/eohippus.html (1)
quote:
Eohippus was a descendent of the Condylarth, a dog-sized, five-toed creature that lived about 75 million years ago. It lived during the early Eocene period, which took place 50 to 60 million years ago. Eohippus, which means "dawn horse," stood about twelve to fourteen inches at the shoulder and weighed about twelve pounds. It looked nothing like a horse. It had an arched back, short neck, short snout, short legs, and a long tail. Its color probably most resembled that of a deer, a darker background with lighter spots.
The legs of Eohippus were flexible and rotating with all major bones present and unfused. It had a choppy, up-down gait and was not very fast. There were four toes on each front foot and three toes on the hind. The vestigial toes - two on the front feet and one on the hind - were still present.
It had a small brain and low-crowned teeth with three incisors, one canine, four distinct premolars, and three "grinding" molars in each side of each jaw. Browsing on fruit and fairly soft foliage, Eohippus probably lived in an environment with soft soil, the kind found on jungle floors and around the edges of pools. Since Eohippus walked on the pads of its feet, it was able to cross wet, marshy ground without much difficulty.
The coloration is pure speculation, of course, but the size and stance are based on the physiology of the skeleton. Now lets also look at the Condylarth:
Paleocene mammals of the world (3)
quote:
Back in the northern hemisphere, another family of condylarths, the Phenacodontidae, may include the ancestors of a more familiar ungulate order: The odd-toed ungulates or Perissodactyla, represented by horses, rhinos and tapirs in the recent fauna. Historically, phenacodontids form the core of the Condylarthra. Well-preserved skeletons are known for the type genus Phenacodus, which is a good model of an ancestral ungulate with beginning adaptations for running. Unlike arctocyonids, periptychids or mioclaenids, the phenacodontids are not part of the first wave of condylarths that populated North America. They first appear with the fox-sized Tetraclaenodon in the middle Paleocene of that continent. The appearance of the more advanced phenacodontids Phenacodus and Ectocion marks the beginning of late Paleocene time in North America. The type genus Phenacodus covers the large size range of phenacodontids and includes roughly sheep-sized animals. Members of the genus Ectocion were usually smaller, with a body mass of only 3 kg in the smallest species, but there is some overlap in size between the two genera. Phenacodontids were the dominant mammals in the latest Paleocene of North America and account for up to 50% of all mammal specimens in faunas of that age.

Figure 5: Reconstruction of the late Paleocene to middle Eocene Phenacodus, a sheep-sized herbivore with improved capabilities for running. From Savage & Long (1986).
This is the most "horse-like" image from this site, and it looks much more like a dog than a horse eh? Of course the coloration and fur are speculation, but the size and stance are again based on the physiology of the skeleton.
To see what the skeletons looked like for the four species used for the leg examples at the start we go to:
http://www.flmnh.ufl.edu/natsci/vertpaleo/fhc/Stratmap1.htm (2)
quote:
(NOTE: LINKS INTENTIONALLY BROKEN - this image is copied from the original to save bandwidth, go to the original Stratmap for the links to work).
(Hyracotherium)- This small dog-sized animal represents the oldest known horse. It had a primitive short face, with eye sockets in the middle and a short diastema (the space between the front teeth and the cheek teeth).
Although it has low-crowned teeth, we see the beginnings of the characteristic horse-like ridges on the molars.
Hyracotherium is better known as "eohippus" - which means "the dawn horse." The name also refers to the fact that it lived during the Eocene.
(Miohippus) - Species of Miohippus gave rise to the first burst of diversity in the horse family. Until Miohippus, there were few side branches, but the descendants of Miohippus were numerous and distinct. During the Miocene, over a dozen genera existed.
Fossils of Miohippus are found at many Oligocene localities in the Great Plains, the western US and a few places in Florida. Species in this genus lived from about 32-25 million years ago.
(Merychippus) - Merychippus represents a milestone in the evolution of horses. Though it retained the primitive character of 3 toes, it looked like a modern horse. Merychippus had a long face. Its long legs allowed it to escape from predators and migrate long distances to feed. It had high-crowned cheek teeth, making it the first known grazing horse and the ancestor of all later horse lineages.
Fossils of Merychippus are found at many late Miocene localities throughout the United States. Species in this genus lived from 17 - 11 million years ago
(Equus) - Equus is the only surviving genus in the once diverse family of horses. Domesticated about 3,000 years ago, the horse had a profound impact on human history in areas such as migration, farming, warfare, sport, communication and travel.
Species of Equus lived from 5 million years ago until the present. Living species include horses, asses, and zebras. Fossils of Equus are found on every continent except Australia and Antarctica.
I selected the same species as were listed for the legs above for convenience here - on the original link you select by clicking on the skulls.
So we have a sequence of species that starts with one standing on the fleshy pads of several splayed toes to the modern species that stands not just on one toe but on the toe-nail of that single toe. But that is not all:
http://muextension.missouri.edu/...agguides/ansci/g02740.htm (4)
quote:
A horse's hoof is composed of the wall, sole and frog. The wall is simply that part of the hoof that is visible when the horse is standing. It covers the front and sides of the third phalanx, or coffin bone. The wall is made up of the toe (front), quarters (sides) and heel.
The wall of the hoof is composed of a horny material that is produced continuously and must be worn off or trimmed off. The hoof wall does not contain blood vessels or nerves. In the front feet, the wall is thickest at the toe; in the hind feet the hoof wall is of a more uniform thickness. The wall, bars and frog are the weight-bearing structures of the foot. Normally the sole does not contact the ground.
As weight is placed on the hoof, pressure is transmitted through the phalanges to the wall and onto the digital cushion and frog. The frog, a highly elastic wedge-shaped mass, normally makes contact with the ground first. The frog presses up on the digital cushion, which flattens and is forced outward against the lateral cartilages. The frog also is flattened and tends to push the bars of the wall apart (Figure 3). When the foot is lifted, the frog and other flexible structures of the foot return to their original position.
When the foot is placed on the ground, blood is forced from the foot to the leg by the increase in pressure and by the change in shape of the digital cushion and the frog. The pressure and the change in shape compress the veins in the foot. When the foot is lifted, the compression is relieved and blood flows into the veins again. In this way, the movement of these structures in the hoof acts as a pump.
This is much more difference in a feature than "just an increase in length" (as in an elephants trunk), it is a totally different structure to stand on (eohippus stood on his toes pads, equus stands on a hoof which not only is not a toe pad, but a feature that wasn't present in the eohippus) and it incorporates a new {added\changed} structure to increase blood flow by acting as a secondary pump.
Not only that the effect of changing the foot structure from a flat footed splayed toed eohippus to the single toed equus also involves standing the foot up on the tip of the toe and using each of the bones between the tip and the heel to effectively make the leg longer for faster running while also making it more flexible than just adding length to the bones of the leg. Probably useful for getting through tight spots and to keep from tripping ... it certainly helps horses jumping in shows from hitting that top bar.
Totally different foot structure, coupled with totally different leg structure (with some ex toe bones now effectively used as leg bones).
The question again is how much change is enough? Try walking around the house on the tip of one toe, then compare your foot to that of eohippus.
Enjoy.


References:
  1. Anonymous, "Evolution of the Horse: Eohippus" Sarah's Horse Farm, Updated 10 Aug 2000, Accessed 12 Jan, 2007
  2. Anonymous, "Fossil Horse Cybermuseum" The Florida Museum of Natural History, Updated 8 Jan 2007, Accessed 12 Jan, 2007
  3. Jehle, Martin, "Condylarths: Archaic hoofed mammals" Paleocene mammals of the world, Updated ?, Accessed 12 Jan, 2007
  4. McClure, Robert C. et al "Functional Anatomy of the Horse Foot" Department of Veterinary Anatomy, College of Veterinary Medicine, Updated 10 May 2006, Accessed 12 Jan, 2007
Edited by RAZD, : color change for note bedded within quote

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This message is a reply to:
 Message 1 by Equinox, posted 01-03-2007 1:30 PM Equinox has replied

Replies to this message:
 Message 11 by Equinox, posted 01-18-2007 12:19 PM RAZD has replied
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Equinox
Member (Idle past 5141 days)
Posts: 329
From: Michigan
Joined: 08-18-2006


Message 11 of 25 (377798)
01-18-2007 12:19 PM
Reply to: Message 10 by RAZD
01-12-2007 9:15 PM


Re: Fourth Chain - Horses, Feet to Hooves
RAZD - thanks for that horse one, especially that picture of the skulls. You got right to the heart of this question at the end of that post - “ how much change is enough?”. We need to remember that these are plausible chains - thus we don’t need to show fossils for each single step, nor know the ancestry for certain. Ideally, we are looking for hypothetical drawings over huge ranges, like from invertebrates all the way to rabbits.
Nonetheless, the excellant posts by RAZD are good examples of documented evolution (where the steps are all well known).
Mick-
your examples are good, but are not what we are looking for. The trilobite chain could be useful if we took drawings from, say, a vendian precursor to a trilobite and had drawings showing it morphing into a horseshoe crab, but even that is less change than we are really looking for. The dino to bird one isn't useful because the pictures don't show gradual change (adjacent forms aren't clearly the same creature). It would be good to see a hypothetical morphing of a compsognathus into a penguin, for example. Thanks anyway though.
Edited by Equinox, : Added response to mick

-Equinox
_ _ _ ___ _ _ _
You know, it's probably already answered at An Index to Creationist Claims...
(Equinox is a Naturalistic Pagan -  Naturalistic Paganism Home)

This message is a reply to:
 Message 10 by RAZD, posted 01-12-2007 9:15 PM RAZD has replied

Replies to this message:
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arachnophilia
Member (Idle past 1343 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 12 of 25 (377812)
01-18-2007 1:22 PM
Reply to: Message 7 by mick
01-12-2007 6:57 AM


Re: First Chain - Forams and Transitions
Unfortunately the pictures are a bit blocky and the species aren't named - but it might be possible for somebody who knows about dinosaurs to label some of the species.
genera, anyways. it's really hard to tell what they are from the size of the diagram. the dinosaur below archie is maniraptor of some kind (dromaeosauridae, i would guess), and below him appears to be an oviraptor.
in any case, it's not exactly correct. oviraptors have pygostyles and beaks. the bottom should be a crocodilian from the paleozoic, not a modern croc. (i would have started wirh euparkaria, or something that ends in -suchus)
Edited by arachnophilia, : No reason given.


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nator
Member (Idle past 2169 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 13 of 25 (377815)
01-18-2007 1:27 PM
Reply to: Message 10 by RAZD
01-12-2007 9:15 PM


Re: Fourth Chain - Horses, Feet to Hooves
quote:
Not only that the effect of changing the foot structure from a flat footed splayed toed eohippus to the single toed equus also involves standing the foot up on the tip of the toe and using each of the bones between the tip and the heel to effectively make the leg longer for faster running while also making it more flexible than just adding length to the bones of the leg. Probably useful for getting through tight spots and to keep from tripping ... it certainly helps horses jumping in shows from hitting that top bar.
Mostly, I think the elongated, structure of the leg is for efficient speed.
Really, much of the horse's physiology has evolved for running.
Here is an interesting article about it:
source
A horse’s body is like a huge bellows, McKeever explained. Its breathing is dictated by the movement of its body and is in synchrony with its stride. Horses can inhale only when their front hooves are striding outward, they exhale only when all four legs come together -- the in and out of the bellows.
Unlike human runners who can take a deep breath independent of their leg movements, horses cannot take that extra-deep gulp of air when in full gallop, said Lawrence R. Soma, professor of anesthesia and clinical pharmacology at the University of Pennsylvania School of Veterinary Medicine. That means a horse with a longer stride has more time to inhale and exhale, allowing the horse time to breathe more deeply. Horses cannot increase their breathing rate without running faster or shortening their strides.
The horse with the longer stride has an advantage, because it has more breathing time, Birks said.
Edited by schrafinator, : No reason given.

This message is a reply to:
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arachnophilia
Member (Idle past 1343 days)
Posts: 9069
From: god's waiting room
Joined: 05-21-2004


Message 14 of 25 (377817)
01-18-2007 1:31 PM
Reply to: Message 11 by Equinox
01-18-2007 12:19 PM


Re: Fourth Chain - Horses, Feet to Hooves
The trilobite chain could be useful if we took drawings from, say, a vendian precursor to a trilobite and had drawings showing it morphing into a horseshoe crab,
horseshoe crabs are not related to trilobites in that way.
trilobitomorpha and chelicerata (spiders and horseshoe crabs) are separate subphyla of arthropoda.


This message is a reply to:
 Message 11 by Equinox, posted 01-18-2007 12:19 PM Equinox has not replied

Replies to this message:
 Message 16 by RAZD, posted 01-19-2007 6:25 PM arachnophilia has replied

  
RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 15 of 25 (378144)
01-19-2007 6:14 PM
Reply to: Message 11 by Equinox
01-18-2007 12:19 PM


Tall Order better to take a step at a time?
Ideally, we are looking for hypothetical drawings over huge ranges, like from invertebrates all the way to rabbits.
This is a pretty tall order if sufficient detail is included for each step along the way. While this may be the ultimate goal, it would be better broken down into discussable sub-sets.
A good resource for one of these is "Use and Abuse of the Fossil Record: The Case of the ”Fish-ibian’" By Penny Higgins at
Page not found | Skeptical Inquirer
I note that there doesn't seem to be any issue with the transitions of plants, bacteria, bugs, worms and the like from water to land. The reason, I suspect, is that there is not much morphological (to a creationist) difference between land versions and aquatic versions - a worm is a worm.
Once again it comes down to the degree of change involved in the process. Time and again a creationist will say that change {X} is "micro"evolution and that "micro"evolution does not equal "macro"evolution nor is there proof of "macro"evolution. The question they have is when does the big change that is "macro"evolution occur - generally because they don't understand what "macro"evolution is (mostly it is just a human observation that (X) is more different from (Y) than it is from (Z) - an artifact of human observation).
Thus the question becomes at what point do they think that "macro"evolution has occurred in a sequence like the horses above or in the fishibians in the linked article.
Enjoy.

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