I'd bet that the most useful of these practices were also highly-mobile and cross-fertilized by travellers. (It only takes one.) We now know that humanity's bee

I'd bet that the most useful of these practices were also highly-mobile and cross-fertilized by travellers. (It only takes one.) We now know that humanity's been moving around for a -very- long time. 4500 years is relatively short. "Merv is the oldest and best-preserved of the oasis-cities along the Silk Route in Central Asia. The remains in this vast oasis span 4,000 years of human history." - http://whc.unesco.org/en/list/886 http://whc.unesco.org/en/list/886