Hinduism is older than 8th to 10th century AD. By this time, the Muslims were almost at our door-step in Afghanistan. I'm not sure whether the above evidence proves a hypothesis of a Central Asian origin although I do believe in the Aryan migration theory. One statue doesn't prove much, it could be an aberration.
Oh yes, Hinduism dates back to beyond 3000 B.C. I was just wondering whether the teachings were passed down through several generations until the statues were built. Of course, this is a far-fetched idea and it could be an aberration, as you mention.