I've been following this thread
with some interest. I have little to add.
One thing does need to remembered
about horses. Unless you have lots of 'free' grass (as on the Steppe), they are
expensive animals to keep. In the Middle East, horses have always been 'luxury'
animals, kept by the rich, or maintained by the king for military reasons.
It was NOT a democratic animal. From Ukraine east into Mongolia, however, the
horse **WAS** a democratic animal. It was all that free grass.
As regards the steppe tarpan, my
understanding is it was the feral descendant of the earliest domestic horse
(they were exterminated as pests by the Soviets). The Iceland horse gives
one an idea of what the first horses must have been like -- small, tough,
slow-growing.
Mark.