Why is base-10 the most common positional notation radix for number representation? I understand that number can have multiple representations, and I can conceive that the positional notation system was better adapted for arithmetics than say the Roman numerals system which led to its wide adoption (or at least I'm willing to believe the Wikipedia article that claims so).
My question is about the common adoption of the radix 10. It's commonly believed that the number was motivated by the natural count of our human fingers, but was this ever demonstrated?
As a programmer, I sometimes have to explain to newcomers the difference between binary, octal, decimal and hexadecimal systems. I start with the general case (before moving to computer specific cases) and usually enjoy pointing out that the base-10 system is more common because of the number of our fingers.
I repeated this enough to start doubting it, and now wonder if anyone has ever tried to know for sure if this claim is true.
In short: Are there proofs or studies that show that the wide adoption of base-10 notations were widely adopted because of the number of our fingers?

I suggest a very old book I once proofread for project Gutenberg.
You will see that some non-decimal structures (binery, ternary, vigesimal, ...)  lure in several languages.
And you will also see that in many langugaes numerals are in fact partially derived from names of body parts.
