Comment by deadsy

There are other tooth forms that also satisfy the fundamental law of gearing (constant ratio of angular velocity). E.g. cycloid gearing used typically in mechanical clocks. The involute is popular because its easy to manufacture. It can be auto-generated on a gear hobbing machine- probably less important now with CNC machines, but very important in a pre-digital machine era. The involute is also less sensitive to gear center to center spacing.