How old were the inventors of major inventions?

I came across this fun column the other day listing a number of Famous Inventions, like the airplane, the camera, electricity, the car, etc, along with their inventors. A thought crossed my mind: how old were these inventors when they invented these inventions? Were they young like Marconi, who invented the radio in his early 20s? Or were they old like Gutenberg, who invented the printing press in his early 50s? In short, is there an age demographic that is responsible for producing major innovations?

Let's take a look at the data based on 34 major inventions listed in the article I cited above (thanks to Michael Varley for organizing the data).

Here is what the data looks like for the full sample:

I have to admit, I was a little surprised--the median age is 40 (I was expecting younger). In what follows, I report the age distribution for different centuries. I'll save any commentary for another time and let you draw your own conclusions. Feel free to send me links to any literature related to this issue.

Postscript: The demographics of innovation in the United States. Reports that the median age for an innovator is 47 years. It's also interesting to note the disproportionate share of innovation attributable to immigrants and the children of immigrants. 

Postscript April 16, 2016. 

Interesting comment thread here.