Appearance.  Extinct in America before arrival of red man.  In general use by 5000 B.C.  Intelligence approaches that of elephant.  Stealing horses once capital offense.  Tend to flee when frightened. 
Andites of Turkestan first extensively domesticated.  Determined dominance of Andites in Occident.  For food, travel, agriculture, war.  Hunted by Neanderthalers.  Not domesticated in days of Prince’s staff.  Offered barbarians tremendous military advantage.