c. 3200 B.C.

The set of nearly simultaneous impulses which engendered the Great Reversal c. 3200 BCE are the following: the invention of bronze metallurgy; the invention of the plow; the invention of the wheel; the domestication of the horse; and, perhaps most importantly, the initial emergence of the acute infectious epidemic diseases influenza, smallpox, measles, etc. Mounting evidence suggests that this list should also include catastrophic impacts between the Earth and members of a certain group of comets and meteors known as the Taurid Complex, which group seems to be the debris from a single object originally some 100 kilometers wide that first arrived in the immediate vicinity of the Earth just before or during the retreat of the last Ice Age and has ever since been in a periodic relationship with the Earth — a relationship punctuated most severely during the centuries immediately prior to 3200 BCE. http://www.gravity.org/mythology/myth_iframe_all.html