Yes, but the culture of enlightenment and innovation within Greek and Roman culture had already been falling apart from within. The culture of Classical Antiquity was outcompeted by less enlightened memes.
How so? I'm not sure when, specifically, you're talking about, but the post-expansion Roman Empire still produced such noted philosophers as Marcus Aurelius, Apuleius, Boethius, St. Augustine, etc.
http://vimeo.com/22099396
What do people think of this, from a Bayesian perspective?
It is a talk given to the Oxford Transhumanists. Their previous speaker was Eliezer Yudkowsky. Audio version and past talks here: http://groupspaces.com/oxfordtranshumanists/pages/past-talks