horses and bits

[Max Dashu]

 Stanley Friesen writes,
>Forget bits - there is also evidence, in the form of changes in equine
>anatomy, for domestication at time *preceding* 4000 BC.  Now it is
>possible, even likely, that it was originally domesticated as a food
>animal. However, its transition to a major sacrificial animal, especially
>in association with prestige graves, suggests that by the time the Kurgan
>cultures have emerged it had changed its status to something more
>special.  The general treatment of the horse in ritual in all of the Kurgan
>cultures gives it a central place in their value system.

>Perhaps riding without a bit preceded use of the bit?

This is what I have been wondering. Didn't the Plains Indians ride horses
very well without using metal bits or stirrups? (The latter known to be a
later development in Eurasia, of course.) And if they did use leather
bridles, would that be enough to cause wear in the teeth?

Max Dashu