Posted on 05/05/2005 5:17:03 AM PDT by Aquinasfan
GAINESVILLE, Fla. --- The old gray mare, she ain’t what she used to be, says a University of Florida researcher whose findings show that the evolution of horses had more twists and turns than previously thought.
University of Florida paleontologist Bruce MacFadden momentarily turns his attention away from a prehistoric horse skeleton on Tuesday, March 15, that is on display at the Florida Museum of Natural History on the UF campus. Conventional notions about how horses evolved are now outmoded, said MacFadden, who describes these changes in an article in the March 18 Science magazine. Horses did not uniformly get progressively larger over time, nor did they make a smooth transition from nibbling on shrubs to eating grass on the open plain, he said. (University of Florida/Kristen Bartlett).
According to conventional notions, horses simply became bigger over time and switched from being diminutive shrub nibblers to the statuesque, grass-eating masters of the open plains, said Bruce MacFadden, a UF paleontologist whose article appears in this week’s issue of the journal Science. But the new horse sense is that the equine mammals are adaptable critters whose size, diet and range depended on geography and climate, he said.
“The old ideas about how horses evolved made for a fairly simple and tidy story,” said MacFadden, whose 1992 book “Fossil Horses” is considered the definitive work on the subject. “But many of the concepts about horse evolution that came into being during the 20th century are now outmoded, giving way to an understanding of the fossil horse sequence that is much more complex.”
Because horses have been around a long time, learning about their evolution provides unusual insight into the patterns of evolution in general, said MacFadden, who works at UF’s Florida Museum of Natural History. “Horses are a very good example because there is a long, continuous fossil sequence of horses extending 55 million years in North America, providing the tangible evidence to trace individual steps or changes in evolution over a prolonged period of time,” he said.
MacFadden said horses are credited with shaping human history more than any other domesticated animal. However, it behooves us to be cautious when accepting other beliefs about the popular animals, he said.
Children often learn in social studies classes how the Spaniards brought horses to the New World in the 1500s, eventually producing vast herds of wild horses on the prairies and helping to create America’s legendary cowboys, MacFadden said. But the fossil record shows horses actually originated in North America at least 55 million years ago and roamed the continent before becoming extinct at the end of the last Ice Age, about 10,000 years ago, he said.
Scientists once universally thought the more primitive horses, which lived from about 55 million to 20 million years ago, were primarily leaf-eating browsers, only becoming grass eaters as the prairie grasslands began to spread rapidly across North America during the Miocene Epoch about 20 million years ago, MacFadden said.
The reality is not so clear cut, MacFadden said. Actually, during times of transition, some groups of horses actually became mixed feeders, eating both grasses and leafy material, he said.
MacFadden analyzed the chemistry of fossilized teeth to determine horse diets. Animals incorporate into their skeletons and teeth the carbon content of the plants they eat, he said, and grasses photosynthesize carbon differently than do leaves, shrubs or trees.
John Flynn, Frick Curator of fossil mammals at the American Museum of Natural History, said MacFadden’s findings are important because the history of horses has been one of the mainstays of evolutionary studies, biology textbooks and museum exhibits since the 1800s. “Bruce MacFadden’s Science ‘Perspective’ on horse evolution elegantly summarizes the latest information on their fossil record, and the knowledge that continues to arise from a wide variety of analyses of both new discoveries and existing fossils,” Flynn said. “And there’s no one better than Dr. MacFadden to provide this synthesis, since Bruce has long been a world leader in understanding horses, past and present.”
Although modern horses are primarily grazers, they will feed on fruits and leaves when grass is in short supply, MacFadden said. “Horses are highly adaptable,” he said. “They can exploit different food resources when they have to and are able to withstand a wide range of climates. They live in the tropics. They extend all the way up to the Arctic.”
Just as the scientific knowledge about whether horses were browsers or grazers has changed, so have ideas about the evolution of body size, he said.
The preconceived notion that the horse was once as small as a dog but progressively grew to its present stature now can be proven to be incorrect, MacFadden said.
About 20 million years ago during the Miocene Epoch, horses diversified in size rather than just becoming larger, MacFadden said. While some grew larger, others became smaller or remained the same size, he said.
MacFadden, who was able to estimate the body size of various species of fossil horses by measuring their teeth because they are proportional to the rest of the body, said the old idea was based on the research of 19th-century paleontologist Edward Drinker Cope. Cope’s Law states that within any group of animals there is a tendency for the descendants of a species to grow increasingly larger.
“But there are so many exceptions where you go from small to large and back to small again that you have to ask how many exceptions to the rule you can accept before the central concept is no longer correct, he said.
What scientists learn about fossil horses has implications for understanding other animals because they are one of the classic textbook examples of evolution, MacFadden said. Descriptions of evolution in college textbooks often show family trees depicting the lineage of the horse, he said.
Nominee for an ID ping
Ping!
Uh huh.
If you knew anything about the Theory of Natural Selection, you would recognize that this variation in size as well as other characteristics is EXACTLY what Darwin would have proposed. Differentiation allows for selection. This is a PRO evolution article. Had horses increased in size over time in a linear progression regardless of habitat changes and other environmental stresses, it could have suggested a mechanism other than Natural Selection was at work, but not ID. In fact, evolution takes place over vast amounts of time in both cases. Noah must have had at least one boat dedicated to nothing but horses.
Of course it is. Everything proves evolution. There is no other possible explanation.
I should note there is nothing in this article about evolution. It is all about adaptation.
According to the article, horses appeared 20 million years ago. They did not evolved from another species, they appeared.
This has been known since about 1940 and many people have tried to point out the mistakes in the so called horse evolutionary line, this was all manufactured to push the evolution theory. They knew it was wrong but kept it in school books anyway along with lots of other misinformation about evolution. Nice to see the truth, actually only part of the truth about horses, come out publicly.
Yup. But evolutionists like to conflate adaptation with evolution, for obvious reasons.
I think what Aquinasfan and others are suggesting, is more along the lines of this:
"Evolutionists have long pointed to the simple, direct lineage of the horse as evidence of natural selection at work. Anyone daring to suggest that the fossil record might be misleading is immediately derided as an ignorant, superstitious Luddite or worse. And yet we find that the purported 'straightforward' evolution of the horse -- as suggested by the fossil record as it was known at that point-- was in fact misleading. Why, then, should it be thought incredible that there is uncertainty concerning other aspects of evolution?"
To which the canonical response is: "Evolution is a fact; the changes in the model governing our equine friends not only demonstrates evolution, but proves that science itself evolves in response to accumulation of additional data. When was the last time a Creationist ever changed their mind about anything, no matter what the evidence?"
In other words, I bet the Cre's would give the Evo's much less grief if the Evo's weren't so smug, given the cases where specific evolutionary pathways have been proven erroneouss. And I bet the Evo's would give the Cre's much more, well, "cre-"dence :-), if the Cre's didn't seize on any anomaly as overthrowing the entire logical framework.
Full Disclosure: Get Off Your High Horse, already!
Cheers!
I'll ping, but only as an interest in the topic.
This is an article that can be an argument for natural selection. "Horses growing diversly" and subsequently having some die out would be a strictly evo argument.
Though it DOES challenge conventional wisdom about an increase in size as being the "eventuality" in horses that they evolved to.
And the scenario here would suggest that MORE horses should exhibit the smaller statures than presently do, given the lack of "hostile" environments to a shorter horse. Anywhere a miniture horse CAN exist, there should be a more diverse sample of such (if the other breeds indeed "evolved" from these smaller creatures.)
That's what I see it as. Or like finch beak variation. Evo's can make their own determination.
The big story here, IMO, is that a bona fide paleontologist has wittingly or unwittingly, moved a case of "rock solid" evidence for evolution into the category of ambiguous evidence, at best.
And the textbooks soldier on with the old story, of course.
And then there's the aspect to the story of scientific orthodoxy being overturned; "most scientists" can be wrong; textbook evidence can be wrong.
"Evolutionists have long pointed to the simple, direct lineage of the horse as evidence of natural selection at work. Anyone daring to suggest that the fossil record might be misleading is immediately derided as an ignorant, superstitious Luddite or worse. And yet we find that the purported 'straightforward' evolution of the horse -- as suggested by the fossil record as it was known at that point-- was in fact misleading. Why, then, should it be thought incredible that there is uncertainty concerning other aspects of evolution?"
You read my mind ;-)
NFP
bump later
Not really they are evolving into extra terrestrial theories
trying to buy some time till they can come up with another God denying plan...
The little horse was probably picked up by ETs who tweaked the horses DNA a bit then returned a few breeding pairs...;)
Naturally when the so called ETs show up and start telling
folks this is what they did...
Well...stayed tuned for if and when this happens it should
make some for some interesting Letterman/Leno guests.
Luddite! 8-)
No it wouldn't. The successive small changes in a particular direction is the hallmark of Darwinian theory. Habitat changes and evironmental stresses are a given.
good call Garth.
You are factuall incorrect. Natural selection does not propose 'small changes in a particular direction". Environmental stresses creates evolutionary winners and losers. The winners do not "adapt" to a change in environment, they merely survive. The genetic advantage they have for survival existed as a result of variations in the gene pool due to genetic drift. The genetic differences existed before the particular selection event took place. It only became an "advantage", after the event. If a different selection event had occured, the same genetic difference may have been fatal.
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