I suggest language played a major part in all early inventions and innovations as a way for those prehistoric engineers to bounce ideas around. Let me add to the example previous quote - "Let's all make some new spears and then log-roll our heavy fat deer home and roast them tonight."
Which probably led to campfire discussions (with full tummies) about better ways to make spears, better ways to make fire, better ways to manually machine flint, and improvements to the concept of the wheel ("Hey Gronk, what if we somehow fastened those logs to a platform so we won't have to keep moving them from back to front?".
If not for language and translators and measurements and the printed word followed by machines to print words (and librarians), none of the progress in later centuries would have happened.
Therefore I suggest that the development of language was the enabler for all the technological progress that followed.
Sophisticated language that actually conveyed ideas, not the springtime birdsong that says "This is my tree, all males stay away, females welcome...", or the grunts, growls, barks, and whines that many creatures use to convey threats, submission, hunger, and mating invitations. While this could be considered basic language, it cannot say anything as complex as "I'm cold. Build a fire."
Early humans had the good fortune to be blessed with a vocal tract that was initially intended for eating and breathing, but became a method for modulating sound into meaningful harmonics. Without that ability humans might still be competing with gorillas for food.
I like your answer. And since the question asked included "what was the most innovative century?" I was going to answer, the 19th century.
Or if we could go off grid a little, I would say the century from 1830 to 1930. Most of the fundamental scientific discoveries that enabled everything that has come along since then were made during that 100 year period.
Fuel (or the controlled use of). Of course, fuel comes in many forms, but going back to the first fires to deliver warmth and cook food. [A side question - why did we ever start to cook food?]
The utilization of different types of fuels in different capacities has been a prerequisite to almost every major period of innovation. Wood, Coal, Oil, Fusion (hopefully). Each exponentially increased our capacity to develop as a civilization.
A reader named Roxy emailed these comments: I had to answer your question about the innovation of 1100's compared to today. If we could be half as creative we would still be lucky. I can't imagine memorizing drawings from sand pits or tables and working toward an image that has never been seen, and wich may not be completed in your life time. It never occurred to me that any on those earlier buildings fell down because of design flaws. In my ignorance I didn't realize the ones that remain are only the success stories, explained as being "right in God's eyes". Considering that most of the work force were illiterate and work conditions were brutal the whole building process must have been a challenge to organize and keep on track.
The craftsmen made their own tools and often invented new ones as needed, we would never be able to match the skill, dedication, and work ethic of the time.
And when asked about favorite innovation from the book...
It's been some time since I read either of the books but I would have to agree that the single most dramatic or at least the most significant innovation was the flying buttress. Although seeing those very high stone walls with wonderous images in stained glass and light are still very impressive today, it must have been very awe inspiring to the local peasants.