Skip to comments.New Insight Into Horse Evolution
Posted on 07/03/2005 2:03:06 AM PDT by nickcarraway
Genetic evidence is shedding new light on the origins of horses in the New World, during a particularly hazy period in their evolution.
As the Great Ice Age came to an end, some 11,000 years ago, North America was thought to be home to as many as 50 species and subspecies of horse.
But studies of ancient DNA tell a rather different story, suggesting the horses belonged to just two species.
These are the stilt-legged horses, now extinct, and the caballines.
The caballines are thought to be the ancestors of today's domestic horse.
"It looks like, as far as we can tell from the DNA, there is only evidence of two species in North America," Dr Alan Cooper from the University of Adelaide, Australia, told the BBC News website.
"We think that, in fact, people have been looking at these fossils and over-interpreting signs of changes in shape and size," he added.
"Probably these animals are adapting to local environments and perhaps they are [anatomically] more [changeable] than the palaeontologists had perhaps thought."
The work has implications for understanding other animals because horses are a textbook example of using fossil evidence to explain evolution.
Although the horse fossil record is very rich, our picture of when and where different species arose is clouded.
Analysis of mitochondrial DNA from fossilised bones, only possible in recent years, gives scientists a new tool to study evolution.
In research published in the open access journal Plos Biology, Dr Cooper and colleagues at Oxford University, UK, analysed mitochondrial DNA from fossilised horse bones.
Mitochondria, the powerpacks of the cell, have their own DNA and are inherited along the maternal line. Their DNA mutates at a stable rate, allowing researchers to look back in time at when different species diverged.
The Oxford research suggests that the stilt-legged horse, which was thought to have migrated into North America from Asia, at a time when the continents were linked by a land bridge, appears, in fact, to be native to North America.
And the Patagonian Hippidion horse found in South America appears to be much younger than previously thought.
It probably moved into South America about 3 million years ago, when the gap between North and South America closed up.
This was a seminal period of evolution, when animals from the two continents were able to mix after a long period of isolation.
My brain hurts....
Actually, I didn't realize that there was any doubt involved. I don't follow closely, but on my last reading the conclusions were that horses were descent from the "Eohippus".
Now in doing some quick research, I've run across a site stating in detail why the evolution of the horse, as stated in previous text, is a fraud. Take it for what it's worth I suppose.
Interesting either way. The Eohippus was said to make it's appearance some 55 million years ago. 50 different subspecies existing some 11,000 year ago isn't such a surprise to me. I don't see their evolution as being limited to a single line resulting in our modern horses. It could have been a series of experiments in design arriving at our present day species. Many people believe the same of early man, who may have faced competition from co-existing with several other man-like species. Even cro-magnon man may have had encounters with the neandertal. So it's not such a leap of imagination to believe in 50 different subspecies of horse.
Of course, more detail would be useful. Yet my coffee is done and my addiction is compelling me to leave my fellow FReepers with the Monty Python GIF, then make a quick exit.
Cool post. Thanks!
Now why would professional scientists do such a thing???
Never mind. I know.
Gotta prove something.....
Let's cut to the chase...I think someone's playing the Race Card again...
Ohio Voter Fraud!!!
As the Great Ice Age came to an end, some 11,000 years ago, North America was thought to be home to as many as 50 species and subspecies of horse. But studies of ancient DNA tell a rather different story, suggesting the horses belonged to just two species... The caballines are thought to be the ancestors of today's domestic horse... The Oxford research suggests that the stilt-legged horse, which was thought to have migrated into North America from Asia, at a time when the continents were linked by a land bridge, appears, in fact, to be native to North America.Fascinating that the horse appears to be native to North America. I believe the same used to be said of the wolf and all domesticated dogs. I doubt that these findings will catch on. I would like to think that they would lead to the demise of mtDNA GIGO.
Mitochondria, the powerpacks of the cell, have their own DNA and are inherited along the maternal line. Their DNA mutates at a stable rate...Heh... Please ping me, if you see articles appropriate for GGG ping.
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
I wish I had me one of them three-toed horses. It would save a fortune on farrier's bills.
I wasn't aware that anyone thought otherwise.
Why, it is undisputable; and any doubter needs only to take a look at Kansas School Board.
Maybe, maybe not. They were pad-footed, kind of like a dog, but with little "hoofies" on their toes. You might have had to have the farrier shoeing 14 little hooves per horse. The Eohippus was also a fairly small critter, about the size of a dog.
On the plus side, they were browsers instead of grazers. I wonder if they ate salal and blackberry bushes? :-)
OK, what gives here? How is it that fossilized bones can contain any DNA. Isn't everything replaced during the fossilization process. I've really got to get out from under this rock more.
Creationist horses say that they aren't related to these earlier horses and say it's a fraud.
There are a number of ways for organic material to fossilize, the most common is by replacement and that is the one everyone is aware of. However, under certain conditions, a type of fossilization called permineralization can occur where the pores and voids are mineralized but some material remains bone. In most cases of this, depending on length of time the fossil is unexposed, even the remaining bone is eventually replaced. With something as recent as North American Equids and Equines many fossils are simply permineralized.
If you are interested, Google on 'Taphonomy'.
Creationist horses are saddled with a poor understanding of the fossil record, how fossil identification is performed and a vested interest in the absence of any transitional forms.
Thanks for the ping!
Did some looking around and didn't find anything all that convincing(to this layman). Fact is, I didn't find an article in my brief search that attributed any DNA from "permineralized" fossils. From this(one of the less academized) article they seem to imply that amber and similar substances which hermetically seal the future fossil(shades of Jurassic Park), is about the only way to retain any DNA over long periods of time.
Amber and Copal:
In amber and copal specimens, an organism becomes entrapped over a relatively short period of time in the various plant resins [exuded from trees such as Agathis, Araucaria (Araucariaceae), Bursera, Protium (Burseraceae), Hymenaea (Fabaceae), Liquidambar (Hamamelidaceae), Pinus (Pinaceae), Shorea (Dipterocarpaceae), and various Taxodiaceae-see Langenheim (1969) for a detailed breakdown of plant sources] that form copal and amber [Schlüter (1990) and Henwood (1992a) give detailed accounts of the imbedding process for specimens in amber and Pike (1993) and Henwood (1993) discuss taphonomy and collecting bias]. Though what is found in these amber and copal media is the actual specimen that died from thousands to millions of years ago, in many specimens, some amount bacterial action may have taken place over time and membranous material supporting the exoskeletal sclerites is often missing. Thus, when one attempts to recover the entrapped specimen by dissolving the amber or copal in a solvent, the result is often a disappointing slurry of floating chitinous plates. However, in some specimens preserved in this fashion, little or no decay has taken place and some muscle tissue complete with mitochondria survives and DNA can still be recovered (Henwood, 1992b). This had led to the exciting field of paleomolecular entomology in which the DNA of fossil organisms over 100 million years old can be studied and comparisons made with putative extant relatives.
Also, at the end of this same article, this item(specifically referring to insects???):
Other Forms of Preservation or Recovery:
Some forms of preservation of fossil insects do not encounter deterioration or mineral substitution of any kind. Those listed in this catalogue include subfossil and tar pit or brea recovery. The ages of these types of fossils listed in this catalogue are relatively young (most from the Pleistocene or Pliocene). In these fossils, all or parts of the insect specimen are visible in three dimensions much the same as those imbedded in amber or copal. Subfossil recoveries of Diptera have been made in peat bogs, caves, and ancient middens of small mammals.
Now if that says what I think it says, THESE specimens should have every cell intact. Which would lead one to believe the DNA would also be intact??? Color me confused.
DNA could be intact, but there's still the problem of cosmic ray bombardment. Some probably good DNA has been extracted from some very old termites in amber. Abstract here. While the DNA had generally been shot up badly, a recognizeable fragment coding for ribosomes was isolated and studied.
The origin of M1 mitochondrial DNA haplotype
University of Cambridge, McDonald Institute for Archaeological Research
Posted on 06/23/2005 8:57:34 AM PDT by SunkenCiv
GEEZ! Always something. Did some snooping around to learn a little about cosmic rays; found this interesting piece from HERE:
What happens when they hit earth?
The combined energy of all the cosmic rays approaching Earth is massive. Fortunately the atmosphere and magnetosphere [§] protect us from them as effectively as a slab of concrete four metres thick. Even so, when cosmic rays collide with atoms in the upper atmosphere, they release showers of gamma rays, X-rays and subatomic particles. Most of these secondary particles will make it to the Earths surface. And the most energetic fragments, although rare, are capable of penetrating miles underground. 
Atomic structures mainly consist of space - space between the nucleus and electrons, space between the individual atoms. Because of this, sub-atomic particles can travel a great distance before they collide with anything. Consequently most cosmic rays and secondary particles pass right through houses, trees, rocks, birds and humans. But a few will occasionally crash into atoms within these structures and beings. Dont be too alarmed; this cosmic radiation is minor compared to the Earths natural background radiation, which in total hardly affects any of us at all anyway.
Thousands of rays and fragments pass through our bodies every minute.  Outside of the Earths atmosphere, where some satellites and astronauts roam, cosmic rays are very dangerous indeed - their sheer frequency means they can ionise electronic circuitry and mutate the genes of astronauts.
Now, what I found interesting is the author, at least in this snippet, said the actual cosmic rays never make it through our atmosphere(only acting as a super collider it seems), but then goes on to consistantly discuss them as if they do make it this far. Color me more confused!
In any case, my point was that it would seem that DNA is being extracted from something other than these extremely rare hermetically sealed fossils. That is, they are able to extract DNA from what is essentially........rock?
So did I miss something?
The idea that underpins this dating technique is that mitochondria, like some kinds of bacteria, do not have sex...
I might suggest a nice dinner and a good wine...
So did I miss something?
Were you trying to?
...my point was that it would seem that DNA is being extracted from something other than these extremely rare hermetically sealed fossils. That is, they are able to extract DNA from what is essentially........rock?
No, not rock. Does that help?
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.