Re: Equids
Phillip Bigelow (n8010095@henson.cc.wwu.edu)
Thu, 29 Dec 1994 08:40:05 GMT
whittet@shore.net (whittet) writes:
>The reported extinction of the horse in the Americas after sixty some odd
>million years of sucessful adaptations, followed virtually immediately
>by the reintroduction of virtually identical sucessors in the same
>enviornment seems odd. The horse seems to have survived both climate
>changes and the introduction of man in the Americas. What killed it off?
>When did this occur? Did some gradual dimunation of its range occur as a
>result of its approaching extinction? Might there have been some survivors
>even so late as to have contributed to the genetic pool of its sucessors?
While you guys are discussing the different modern breeds of the modern
horse, it might help the discussion if you considered the fossil record.
The "virtually identical successors" that you assume, actually weren't
identical, at least for North America. The North American Equus was of a
different species, and in fact, this is demonstrable from the fossil record.
There are twelve different species of Equus from the last 4 my of North
America, all extinct, and all clearly distinguishable from the Eurasian
Equus. The following list was compiled from
Groves, C.P. 1974. Horses, Asses and Zebras in the Wild.
Ralph Curtus Publishing, 192 pages.
E. shoshonensis at 3.5 my.
E. rubustus at 3.0-1.0 my.
E. sellardsi at 3.5 my.
E. fraternus at 400,000 - 200,000 ya.
E. complicatus at 200,000 - 100,000 ya.
E. occidentalis at 100,000 - 10,000 ya.
E. andium at 400,000 - 200,000 ya.
E. neogaeus at 200,000- 10,000 ya.
E. conversidens at 200,000- 10,000 ya.
E. scotti at 200,000 - 10,000 ya.
E. laurentius at 200,000- 10,000 ya.
E. ferus (Przewalski's Mongolian Wild Horse) poorly-dated fossil remains
in Alaska (_only_ Alaska).
<pb>
>Would you eliminate the possibility that some native horses survived to
>contribute some genetic material? Would it be possible to test the DNA of
>horses to exclude that possibility?
We don't know what the gene sequences would be for native American horses,
so we wouldn't know what to look for in the sequence to demonstrate
homology. On the other hand, DNA comparisons of the re-introduced North
American mustangs with the DNA of European breeds would definately prove
that the mustang came from Europe. I don't know if it has been done.
<pb>
>Why did so many breeds evolve from the single
>source so quickly?
It's the same with breeds of dogs. You can achieve a new breed in as
little as 20 generations, with proper attention paid to the characteristics
that are desireable.
<pb>
>I am by no means certain that the horse
>did survive in the Americas, even in pockets, or that it was ever
>domesticated in the Americas, even thousands of years prior to the Spanish
>and the event of its extinction, but I have no evidence as yet to exclude
>the possibility either.
>I don't know if there are enough fossil records to clearly identify the
>pattern of the horses decline and re-emergence in the Americas, or to
>show if there was evidence of domestication such as tooth wear and tarter
>buildup from eating grain.
The only conceivable way to deal with this question is to establish the
fossil record of E. ferrus (Przewalski's Mongolian Wild Horse) throughout
the North American continent. As the list above shows, fossil evidence
(although sparce, and in dispute by some) shows a E. ferus-like horse in the
fossil record of Alaska. But the fossil species is not found anywhere else in
North America, and the introduced wild mustangs in the Pryor Mts. of Montana
do not resemble the Przewalski Mongolian Wild Horse, at least in my opinion.
Horses went extinct in North America at the close of the Pleistocene.
<pb>
>Getting back to my original line of thinking, what if the horse was
>domesticated in the Americas, long before the time of the Spanish,
>isn't it as plausible to imagine people migrating from the Americas
>to Siberia with horses, as coming the other way without them?
>Steve
It's possible to imagine anything, I guess. If you don't mind my asking,
but why do you think this is so? It never ceases to amaze me how, in spite
of abundant fossil evidence to the contrary, people will believe what they
want to believe. Archaeological evidence abounds in Eurasia for the
domestication of the horse there. None exists in North America, and in
addition, there is fossil evidence of an extinction in North America. You
are really fighting your way upstream on this theory, pal.
<pb>
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