mitschlag
Posts: 236
Joined: Sep. 2006
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Contra Schindewolf, Part 2 (On horse toes - dialog with George)
I believe that this is where toes were introduced into the discussion:
| Quote (Daniel Smith @ Sep. 28 2007,03:31) | | Quote (Alan Fox @ Sep. 27 2007,11:25) | | If you recall, this thread was originally intended for you to show how the evolution of the horse is a problem for the current theory of evolution. I have not seen a great deal of evidence from you, yet. |
You're right.
In order to keep this thread on topic, I will try to keep my posts focused on the work of Schindewolf and Berg and (at least in the case of Schindewolf) also on the evolution of the horse.
Berg doesn't say a lot about horses other than this from section IV, "Convergence":
| Quote | "At the very time when in North America the Equidae were being evolved, forms of the order Litopterna were being elaborated in South America in the plains of the Argentine. The latter are extinct ungulates, in many respects recalling horses: they had also lost the lateral digits of their limbs, and for progression made use of the median digit; their extremities and neck were likewise lengthened, and in the former, the ball-and-socket joints, by which movements in all directions could be accomplished, were being gradually supplanted by pulley joints, which restricted their limbs to being moved only backwards and forwards; their teeth lengthened and grew more complex (although no cement was present). This group was extinct in South America before the arrival of horses. The Litopterna, or pseudo-horses, thus copied the horses in many ways.
The same course (as to limbs and teeth) as in horses was followed in the evolution of camels in the New World, and of deer, antelopes, sheep and oxen in the Old" |
Nomogenesis, pg. 212.
As for Schindewolf's position, why don't I just start by using the same quote I provided for you over at Brainstorms: | Quote | To this extent,the one toed horse must be regarded as the ideal running animal of the plains. It's early Tertiary ancestors had four digits on the front feet and three on the hind feet, and low crowned cheek teeth. Since in the later Tertiary, an expansion of plains at the expense of forests has been observed, this change in environmental conditions and the consequent change in the mode of life has been represented as the cause of linear, progressive selection leading up to the modern horse.
However, in the formulation of this view, not enough consideration has been given to the fact that the evolutionary trend of reduction in the number of toes had already been introduced long before the plains were occupied in the early Tertiary by the precursors of the horse; these inhabited dense scrub, meaning that they lived in an environment where the reduction of the primitive five-toed protoungulate foot was not an advantage at all. In the descendants, then, the rest of the lateral toes degenerated and the teeth grew longer step by step... regardless of the mode of life, which... fluctuated repeatedly, with habitats switching around among forests, savannas, shrubby plains, tundra, and so on.
If selection alone were decisive in this specialization trend, we would have to ascribe to it a completely incomprehensible purposefulness... |
Basic Questions in Paleontology pp. 358-359, (emphasis his)
Both of these men intently studied real examples from nature and the fossil record and came to the same conclusions:
1. That evolution of types happened suddenly - not gradually.
2. That subsequent evolution proceeded as if constrained by laws.
3. That natural selection had nothing to do with the formation of any organ. |
George challenged Daniel on Schindewolf's claim that reduction in toes preceded the appearance of plains on the planet. Daniel responded:
| Quote (Daniel Smith @ Sep. 30 2007,16:56) | | Quote (George @ Sep. 28 2007,07:44) | | Quote (Daniel Smith @ Sep. 28 2007,03:31) | | Quote | However, in the formulation of this view, not enough consideration has been given to the fact that the evolutionary trend of reduction in the number of toes had already been introduced long before the plains were occupied in the early Tertiary by the precursors of the horse; these inhabited dense scrub, meaning that they lived in an environment where the reduction of the primitive five-toed protoungulate foot was not an advantage at all. In the descendants, then, the rest of the lateral toes degenerated and the teeth grew longer step by step... regardless of the mode of life, which... fluctuated repeatedly, with habitats switching around among forests, savannas, shrubby plains, tundra, and so on.
If selection alone were decisive in this specialization trend, we would have to ascribe to it a completely incomprehensible purposefulness... |
Basic Questions in Paleontology pp. 358-359, (emphasis his) |
So basically Schindewolf is saying that horses developed single-toed hooves regardless of the selection pressures applied? How does he know what those pressures were? How does he know the scrub was dense? Paleoecologists today can identify what species were present in the landscape at a point in time, but have much more difficulty in determining vegetation structure. This has led to disagreements over what the European landscape of most of the Holocene was. Yes there were lots of oak trees present, but was it closed forest? Was it patches of scrub interspersed with grassy plains? Was it widely spaced parkland-like trees?
In other words, what was the quality of his data and how far is he spreading it with rhetoric? |
He doesn't go into any details (in this book at least - he may have in others or in one of his papers) about how he knew the environmental conditions were such as he described, so I can't tell you how he determined that.
I'm assuming that the man described in 1965 by Stephen Jay Gould's advisor, Dr. Norman Newell as "the greatest living paleontologist", used the scientific method and the accepted evidence of his day to determine these factors.
You might be in a position to show that he made a false claim, but you must base that on evidence from that time period. |
And then:
| Quote (Daniel Smith @ Oct. 01 2007,19:37) | | Quote (George @ Oct. 01 2007,07:22) | You misunderstand me. I'm not saying he was lying. I'm questioning how he knew what Tertiary environmental conditions were like and how good were the data he based his conclusions on. As I said before, it is difficult enough for today's paleoecologists to reconstruct past vegetation. It would have been much more difficult and imprecise for the ecologists of a century ago. Palynology, one of the more powerful tools, was only in its infancy.
To summarise: he may have based his theories on the understanding of the day, but if that understanding is wrong, his ideas crumble. |
Schindewolf's book was published (originally - in German) in 1950. While technically that was in the last century, (so was 1999), it wasn't "a century ago".
This is what he said:
| Quote | Since in the later Tertiary, an expansion of plains at the expense of forests has been observed, this change in environmental conditions and the consequent change in the mode of life has been represented as the cause of linear, progressive selection leading up to the modern horse.
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(emphasis mine)
I assume "has been observed" means that it was well accepted. Perhaps newer data has proved him wrong, I don't know. |
And yet again:
| Quote (Daniel Smith @ Oct. 03 2007,02:22) | | Quote (George @ Oct. 02 2007,07:57) | | Quote (Daniel Smith @ Oct. 01 2007,19:37) | | Schindewolf's book was published (originally - in German) in 1950. While technically that was in the last century, (so was 1999), it wasn't "a century ago". |
My mistake. I thought you said he worked and wrote in the 1920s. |
Perhaps you were thinking of Leo Berg? He wrote Nomogenesis in 1922. | Quote |
I wasn't questioning this statement:
| Quote | Since in the later Tertiary, an expansion of plains at the expense of forests has been observed, this change in environmental conditions and the consequent change in the mode of life has been represented as the cause of linear, progressive selection leading up to the modern horse.
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I was questioning this one:
| Quote | | However, in the formulation of this view, not enough consideration has been given to the fact that the evolutionary trend of reduction in the number of toes had already been introduced long before the plains were occupied in the early Tertiary by the precursors of the horse; these inhabited dense scrub, meaning that they lived in an environment where the reduction of the primitive five-toed protoungulate foot was not an advantage at all. |
(emphasis mine)
My question is how did he know the environment at the time was entirely comprised of dense scrub? If I were to guess, this statement is based on finds of macrofossils or pollen of scrub species coupled with other proxy data that gave clues about climate. This may have been the prevailing view at the time. Don't know. Doesn't matter. But I suspect hand-waving. |
So, after admitting that you "don't know" what evidence Schindewolf based his argument on, you say that it "doesn't matter", because you "suspect hand-waving". Is this how science is done?
| Quote | My point is that knowledge of what species were present at the time doesn't give an accurate picture of what the vegetation structure was at the time, especially over large areas. I presume the ancestors of horses were widely distributed and not confined to a small isolated valley or two.
As you can see as you walk around in "the wild", vegetation structure varies considerably depending on climate, soil and other things, including the activities of grazing animals. It is extremely unlikely that the landscape where the ancestors of horses evolved was completely dominated by "dense scrub". It is extremely likely that there were some more open areas where having fewer toes increased fitness.
Schindewolf was overstating the case that the environment required to select for single-toedness was not present in the early Tertiary. Because of this, he has no grounds for claiming that development of the trait preceeded selection pressure. |
So based on your experience 'walking around in the wild', you've now decided that Schindewolf, one of the premier paleontologists in all of Europe, overstated his case? (a case which, I'm sure, was based on slightly more research than that!)
It's amazing to me how you can delude yourself into thinking you have actually refuted his arguments while presenting no evidence to the contrary from the Tertiary period at all! |
At which point, George seems to have thrown in the towel.
More to come...
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"You can establish any “rule” you like if you start with the rule and then interpret the evidence accordingly." - George Gaylord Simpson (1902-1984)
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