Re: Equids

Kathleen Hunt (
30 Dec 1994 01:18:01 GMT

[discussion about whether _E. ferus_ could have survived in the Americas
and given rise to the mustangs..._E. ferus_ is equated to the modern
Przewalski's horse...]

One obvious point that I just remembered: Przewalski's horses have a
different chromosome count than all domestic horses (2n=66 for the
P-horse, 2n=64 for all reported domestic horses). Offhand I don't know if
anyone has karotyped mustangs or old American mustang-derived breeds (such
as Appaloosas), but this would be very easy. Even if the present-day
mustangs have interbred with domestic horses, if they started wit a
P-horse chromosome count, the mustang population should still have some
individuals with 2n=65 and 2n=66. (A Robertsonian chromosomal
polymorphism, as is currently seen in the kiang & related Asian onagers.)

That said...I am reluctant to equate the P-horse with the entire species
of _E. ferus_. Though the P-horse is often taken as a model for all
prehistoric Asian wild horses, my impression is that it is actually a
local Mongolian variant of the Asian wild horse, so other populations of
the Asian wild horse may have differed in various ways (for instance
color; P-horses are uniformly dun with pangare [pale muzzle and
belly] while the Siberian wild horses seem to have been white).

More notes on color: All wild horses tend to carry the dun gene (dilutes
the basic body color and results in a dark stripe down the back). Onagers
and asses have this dun color gene, too. Western European wild horses
definitely had spotting genes, judging from cave paintings. Western
European domestic horses once carried many spotting genes, though spotted
patterns fell out of favor a few centuries ago almost everywhere except
Spain. Tarpans (eastern European) were uniformly grulla (slate-grey, and
carrying the dun gene). The old Bedouin legends of wild Mideastern horses
seem to show they were chestnut or grey (don't know if this means grulla
or if it means the progressively lightening grey), with some spotting
patterns. I may be wrong there as English translations of Bedouin terms
for horse color may be misleading. P-horses are uniformly dun with
pangare (pale muzzle and belly), never spotted.

The noticeable color trait of mustangs are their common spotting
patterns. The mustang population carries the overo allele, the tobiano
allele, the Appaloosa allele accompanied by various poorly understood
modifier genes, the dun-dilution allele, and the cremello-dilution
allele. These genes were all present in the old western European horses,
especially the Spanish breeds. Certainly none occur in the P-horse. I
don't know if any occur in north-eastern Asian domestic breeds.

BTW, genetic studies on the P-horse show it has probably been separated from
domestic horses for about 200,000 years.

And a note on manes: The wild Asian horses had a stiff mane, judging from
the P-horse. The wild horses of western Europe also did, judging from
cave paintings. The wild tarpan of eastern Europe did NOT, according to
historical accounts; it had a floppy mane like domestic horses. (The
modern zoo-recreated tarpan sometimes has a stiff mane; this is because
they were cross-bred with a P-horse stallion several generations back,
because the zoo breeding them thought that would make them look more
"primitive".) The wild desert horses of the Mideast had floppy manes,
didn't they? (straining to remember the details of those Bedouin
legends...) All zebras, donkeys, and onagers have stiff manes. I need
more info on the Alaskan wild horse, though. I was at U.Alaska-Fairbanks'
natural history museum this summer and studied their horse exhibit pretty
closely; they described it as having a stiff mane. But I don't know if
they actually found mummified remains with stiff manes, or if they just
assumed it had a stiff mane.

If I have gotten this right, the only wild equids with floppy manes were
in eastern Europe/Russia, and in the Mideast. Domestic horses mostly
have floppy manes (one exception is the Norwegian Fjord breed; I don't
know its ancestry). Mustangs all have floppy manes.

So far I am still not seeing any real evidence for mustangs being derived
from the prehistoric American wild horse (which I assuming was similar
to the Alaskan wild horse?).

Kathleen Hunt

If we increase the size of the penguin until it is the same height as
the man and then compare the relative brain size, we now find that the
penguin's brain is still smaller. But, and this is the point, it is
larger than it *was*. (Monty Python)