Whole Sort Of Genl Mish Mash
We've learned much about ancient civilization in the past 100 years, but we still don't know all that much.
Building on what Ron wrote, isn't it more probable that these cultures produced mathematic savants ... their own "Rain Men" so to speak? This would also explain why, even when advanced mathematics was practiced by these cultures, they remained very superstitious and never developed a sophisticated philosophy.
Applying Occam's Razor, perhaps autistic savants showed them how to do that.