In other words, yes, we use decimal because we have ten fingers.
dig·it [ˈdijit]
NOUN
1) any of the numerals from 0 to 9, especially when forming part of a number.
2) a finger (including the thumb) or toe.In particular, since our hands can show "10" the natural base this would imply is base _11_ and not 10.
Another argument I've heard presented is that since 10 is divisible by 2 and 5 this simplifies many common calculations. There were groups in the past advocating use of other bases (in particular 12 but also 16).
The mayan's number system is base 20 (though the digits are are drawn out of sub digits in base-5).
I'd disagree. Having base 10 allows us to easily imagine 60 as 6 people worth of fingers.
I think I remember learning in school that one of the ancient Mesopotamian civilizations (Sumerian, I think, but I could be wrong) used 60 as the basis for their system because it was divisible by 1, 2, 3, 4, 5, and 6.
To me, it always seemed like 5 was only a common number because of its place in base 10, not the other way around. There doesn't seem to be any reason that 2 and 5 would have been chosen as more significant than 2 and 3 or 2 and 7.