VARIATION IN DOMESTIC ANIMALS 461 
now represented by the Mongolian or Prejvalsky horse, was a fleet, 
active horse of about 13 hands height, perhaps most distinctively 
characterized by its large head and Roman nose. The modern Shire and 
Clydesdale exh’bit this type of head, and evidently trace along one line 
to steppe ancestors, as do other Roman-nosed breeds. The Siwalik horse 
of India was a tall finely built horse of racing type. Horses of this type 
may have been over 15 hands high, and they had a peculiar promi- 
nence between the eyes which is still met with among some Arabian and 
Indian horses. Some Thoroughbreds today exhibit characters which 
connect them with ancestors of the Siwalik type. The evidence, there- 
fore, is very strongly in support of the belief in the polyphyletic origin 
of modern breeds of horses. In the characters of these ancient ancestors 
of the horse we may find represented practically all the characters of 
modern horses. 
In historic times there is abundant evidence that mixing of distinct 
types of horses was a very common practice. In Europe the fleet, finely 
built horses of the Oriental desert type, particularly the Arab and the 
Barb, have been used freely in perfecting practically all modern breeds 
of horses. At about the beginning of the 18th Century, three Ori- 
ental stallions, the Godolphin Barb, the Byerly Turk, and the Darley 
Arabian were used extensively in England, and from this foundation 
stock sprang the Thoroughbred and Hackney, and later in America the 
Standard bred. As late as 1820 two gray Arabian horses Godolphin and 
Gallipoli were used on draft mares in La Perche, and they had a remark- 
able influence in the direction of superior quality and action in Percheron 
horses. And this is only one side of the story of diversity in the founda- 
tion stock of modern breeds of horses, for without exception they all have 
a comparatively short history of strict matings confined to the breed 
standards. 
The horse has been chosen merely as an example; other kinds of 
livestock show just as striking ancestral diversity. Among cattle there 
is evidence of zebu ancestry in some breeds like the Shorthorn, whereas 
the Aberdeen-Angus seems to trace to an ancient Syrian race. As in 
horses so in cattle there has been much mixing of types within historical 
times. In the case of the domestic fowl, the opinion is usually defended 
that there ig evidence of monophyletic origin, the wild jungle fowl, 
Gallus bankiva being regarded as the common ancestor. But there is 
evidence that the Malay breeds have descended from another species, 
and in view of the freedom with which the Malay breeds cross with other 
breeds of fowl, it may be wise to reserve judgment of the monophyletic 
origin of barnyard fowls. It is, however, proper to state that many of 
the breeds of fowls do show differences which are of the value of simple 
factor differences, or recombinations of a few such original differences; 
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