> Although it is unknown why 60 was chosen

Oh come on. This is not rocket science.

There is an easy way to count to 12 with just one hand: place your thumb on one of your phalanxes. There are three for each of the remaining fingers: hence, 4*3=12 possibilities. Babylonians counted this way, hence the duodecimal system.

You can use your second hand to count to five, as usual. 5x12 = 60. If you show one of the fingers on your left hand, and one of the phalanxes of your right hand, it really clearly communicates a number from 1 to 60.

This is why the base 60 was chosen.