For example, Da Vinci was born in 1452 and the printing press was invented in 1440. So the Renaissance was fully underway in the 15th Century. Others such as Boccacio and Petrarch go back to the 14th Century. But the innovations of that period are based on ideas and break-throughs that go back centuries before that.
The truth is that the Dark Ages were always a misnomer. There were rough decades, such as the decades when the Carolingian Empire collapsed and the Vikings first began pillaging, but on the whole there was a slow steady progress in the six centuries before Luther (with the major interruption of the Black Death). Agricultural innovations had allowed the population in much of Europe to exceed Roman days by the time of the great plague.
I would also submit that a distinction needs to be made between the medieval period and the Dark Ages which preceded them. They're not the same thing.