The question of simultaneouus or multiple discoveries was initiated by Robert K Merton in "SINGLETONS AND MULTIPLES IN SCIENTIFIC DISCOVERY - A CHAPTER IN SOCIOLOGY OF SCIENCE" PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY 105 (5): 470-& 1961. A huge literature in the "old" sociology of science grew from this paper by Merton. You can trace the influence of this paper at http://www.garfield.library.upenn.edu/histcomp/merton_p-am-philo- soc_v105_p470/ E. Roy Weintraub