The earliest primate bipeds originated near the end of the Miocene era to the beginning of the Pliocene era. Plate tectonics and continental drift which occurred in the Miocene era is believed to be the catalyst which created the environment conducive to bipedal development. The collision between Africa and Eurasia caused East Africa to rise in elevation gradually transforming the lush Forrest existing there into a dry savanna. No longer having a rich forest for cover from predators, having to view above tall grasses, and having to search longer distances for food are all contributors, caused by the environment, of bipedal necessity.
Being a nerd, and spending tons of time playing online games, I frequently come across situations where one individual flames another without much or any provocation. Usually the individuals don't know each other, and the degree of anonymity is high. On occasion I have even asked why the person why they felt the need to be so cruel. Among the answers i received was: