TITLE: Underlying Reason For Taking Log Base 10
QUESTION [31 upvotes]: For the equation $2^x = 7$
The textbook says to use log base ten to solve it like this $\log 2^x = \log 7$. 
I then re-arrange it so that it reads $x \log 2 = \log 7$ then divide the RHS by $\log 2$ to isolate the $x$. I understand this part.
I can alternatively solve it in an easier way by simply using $\log_2 7$ on my calculator.
Using both methods the answer comes to the same which is $2.807$
My question is twofold:

Why would the textbook suggest to use log base ten rather than simply using log base two?
I can see how using log base ten and the suggested method in the textbook makes me arrive at the same answer but I don't understand WHY this is so. How does base ten play a factor in the whole scope of things.

Thank you

REPLY [2 votes]: The only reason we use base ten for anything (including decimal numbers) is that biological evolution endowed humans with ten fingers. The Mayans are supposed to have used base twenty, apparently because they were barefoot and thought that toes were convenient for counting too.