Many people think modern running shoes are necessary in order to run safely and comfortably, but they were invented only in the 1970s. Before then, running shoes were just simple running flats that had little cushioning, no arch support, and no built-up heel. Humans were running for millions of years, apparently safely, in running flats, in thin sandals or mocassins, or in no shoes at all. Our research indicates that they may have been able to do so by forefoot or midfoot striking."
For more indepth visit http://www.barefootrunning.fas.harvard.edu/index.html
Also tips on how to..http://www.barefootrunning.fas.harvard.edu/5BarefootRunning&TrainingTips.html