The importance of 12 has been attributed to the number of lunar cycles in a year as well as the fact that humans have 12 finger bones (phalanges) on one hand (three in each of four fingers). It is possible to count to 12 with the thumb acting as a pointer, touching each finger bone in turn. A traditional finger counting system still in use in many regions of Asia works in this way and could help to explain the occurrence of numeral systems based on 12 and 60 besides those based on 10, 20, and 5. In this system, the one (usually right) hand counts repeatedly to 12, displaying the number of iterations on the other (usually left), until five dozens, i.e. the 60, are full.