Indeed, it's very common for something to be invented independently in different places. (Some would go farther, citing evidence that independent simultaneous i

Indeed, it's very common for something to be invented independently in different places. (Some would go farther, citing evidence that independent simultaneous invention is, in fact, the rule rather than the exception.) Further reading: http://www.kk.org/thetechnium/archives/2009/08/progression_of.php http://www.kk.org/thetechnium/archives/2009/08/progression_o...