Scholar Richard Carrier (PhD) says that the Dark Ages were a real time period in history and that in that time period, science, living conditions, and a host of other things declined.
Hello, I wrote about Dr Carrier's opinions on the Medieval Period here.
It should be pointed out that he is a Classicist/Ancient Historian and not a Medievalist in any way. He's also clearly got several axes to grind. His ideas around human 'progression' being based on quantifiable technological 'progress' are also lazy at best, and his work is riven with assumptions.